How much do solar panels cost?

Solar PV panels have reduced in price by approximately 40% as a result of falling manufacturing costs and increased competition in the market. This means you can now get a decent sized solar PV system installed on your roof for between £4,000 and £6,000.

We would always recommend trying to maximise the number of solar panels that you go for – but this is often limited by the size of the roof space.

A 250w solar panel will typically cost between £300 and £500 and each panel is approximately 1.7m². Therefore for a 3.5kW system, you are looking at a price of between £4,200 and £7,000, and this would take up approximately 23.8m².

For a smaller 2.0kW system, you are looking at paying between £2,400 and £4,000 and this size system would take up approximately 13.6m².

Obviously, the more solar panels you have on the roof, the more electricity you can produce. This therefore means you need to buy less electricity from the grid (as you can use the electricity you produce).

You can also get payment from your energy supplier, provided they are signed up to the Smart Export Guarantee (SEG).

The SEG is a legal obligation for any electricity supplier that supplies at least 150,000 customers to offer an export tariff to those with solar panels for each kWh produced.

The actual export tariffs these energy companies offer can be flat, variable or smart rate (adjusting based on wholesale prices), however the tariff must always be greater than zero (even when wholesale prices of electricity are negative).

There is quite a large discrepancy between the different SEG rates from the different providers – for example in August 2020, Utility Warehouse offer £0.02 / kWh, while Octopus are offering £0.055 / kWh.

SEG versus FIT

The SEG was introduced in January 2020 to replace the older Feed in Tariff (FIT) scheme, which closed to new customers on 31st March 2019.

The main difference between SEG and the FIT scheme was that the FIT scheme paid the owner of the solar panels for both producing the electricity and also for exporting it, while the SEG only pays for exporting it – therefore the SEG is far less generous.

Eligibility for the SEG

To be eligible for the SEG, the solar system being installed needs to be under 5MW (or approximately 20,000 solar panels – so most homes should be okay!). The solar system must also be installed by an MSC certified installer. Finally you need to have a smart export meter installed to measure how much of the electricity is being exported back to the grid.

SEG Tariff vs. using the electricity at home

To maximise the return from the solar PV installation, you will want to use as much of the electricity you produce in your home as possible. In the most basic terms, if you use the electricity you produce in the home, then you don’t need to buy it from your energy provider (a saving of around 15p/kWh). If you export it, you only get paid a fraction of this (£0.05 at most!) – so if you can use it in the home, then it is strongly recommended to use it!

By incorporating battery storage technology into your solar system setup – it allows you to store the electricity you produce to use as and when you need it. You can learn more about battery technology by clicking here.

Solar PV worked examples

So, to start with, we will look at a typical 3kWh system (installed on a new build with a ‘higher’ energy efficiency requirement rating) and see the annual return, based on the percentage you use in the home versus how much you export. Over a year, a 3kW system would expect to be around 90% efficient and generate about 2700 kWh of electricity (an average home used 4,800 kWh per year).

Worked Examples – % of Electricity used in the Home : % of Electricity Exported to the Grid

These numbers are correct as of 18th August 2020.

What impacts the initial cost of your solar PV installation?

The cost of your solar PV system is dependent on two things:

1. The size of the installation

Obviously the larger the system you install, the more electricity it has the potential to produce. The average solar PV system installed in the UK now is 3.5KW, which – working at 90% efficiency – will produce approximately 3150kWh of electricity (depending how much sun you get in your part of the country). As reference, an average house uses approximately 4,800kWh. The number of panels you can install will probably be limited by either the amount you can afford or the size of your roof. Suppliers will also charge different prices for their installation services and it’s important to ensure they are MCS-accredited to qualify for the SEG

2. The quality of the solar panels used

Not all solar panels are the same!

See our guide to the different types of solar panels for more details, but in a nutshell there are three types:

• Monocrystalline solar cells (made from single crystals grown in isolation) are the most efficient at 15-22%, but they are also the most expensive type of solar cell.
• Polycrystalline cells are cheaper than monocrystalline, but their efficiency is far lower at just 13-17%.
• The cheapest solar cells of all are amorphous solar cells, which also have the bonus of being more efficient in low-light (great if you live in the UK!) but they are the least efficient overall at 9%.

How are the efficiency figures calculated? Well it is determined by how many watts of power are produced in a square meter. 100% efficiency means that a square meter of panel would create 1,000 watts. Therefore a panel rated at 18% would create 180 watts from every m^2; it follows that panels with higher efficiency ratings create more electricity (per meter squared) and this is reflected in the price.

>>> How solar return changes based on pitch and shading <<<

As you can see in the table above, the actual price of your installation varies depending on the types of panel you get installed, so a 4kW system could cost as little as £4,800, or as much as £8,000. In the table below we have assumed we are exporting 50% (so this is eligible for the SEG) and 50% is used within the home (so a saving on the electricity bill).

Payback of your Solar System

So looking at ‘System A’ in the table above, the system costs £4,800 and the annual return is £320 per year, so it will take approximately 15 years to pay back. In addition, electricity prices are expected to go up over time, so the £0.15 you save for every kWh of electricity you use in your home will actually increase – and could be nearer 20 pence in just 5 years – therefore the absolute return could actually become bigger.

Once you have ‘made your money back’, then any money you make is paid directly to you as profit – so you will be in line to receive the SEG indefinitely while you are exporting electricity.

There are a few other costs to think about with solar PV

Maintenance

There are maintenance costs associated with your solar PV installation, including cleaning them at least twice a year to ensure they are working as efficiently as they can.

Replacing Inverters

In addition, despite the solar panels being good for 20 years plus, the inverters have a lifespan of about 10 years, and replacing these will cost just shy of £1,000 – so factor this in to your calculations when your solar installers give you a quote.

>>> Microinverters can also increase Solar PV return – click to find out more <<<

Insurance

You will need to insure you solar PV array as part of your home insurance, so your insurance premium payments will slightly increase.

Planning Permission

Installing solar panels on your roof does normally not require planning permission. However if you live in a conservation area or world heritage site, you will need to speak to your planning authority to get the necessary permission. Note: there will also be legal fees associated with this.

Installing Solar PV

Are you thinking about installing a solar PV system at home? We have scoured the country for the best tradespeople, so that we can make sure we only recommend those we really trust.

If you would like us to find you a local installer to help install a solar PV system in your home, just fill in the form below and we will be in touch shortly!

If you are a company looking to benefit from the feed in tariffs, there are a few prerequisites that you need to meet. And just like a domestic property, you will need a valid EPC to get the payment.

What is different for a business claiming the Feed In Tariff?

There aren’t really any distinctions made for businesses applying for the tariff, but there are several points that are more likely to apply to a business over a residential application:

-You will need a commercial EPC rather than a domestic EPC if you are getting the panels on a business property.

-The rates paid as part of the generation tariff decrease with larger systems, which generally doesn’t affect small residential systems.

-Businesses with multiple installations at various sites may receive a reduced rate.

What is a commercial EPC?

A commercial EPC is a certificate issued against a non-domestic  property, giving the property an energy rating and an outline of energy efficiency improvements that could be carried out, as highlighted in the recommendation report. The cost of the EPC will vary depending on the type and size of the property, and they are a little different and generally more expensive than a domestic EPC. You can find out all about commercial EPCs here.

How much Feed in Tariff will you get?

A commercial property is more likely to have a larger PV or wind system than a domestic property – for a couple of good reasons: the property will often be larger and have bigger roof space (although not always) and it will often require more energy than a domestic property, especially during daylight hours when PV is most effective.

Imagine a store with rows of large freezers running all day long, and fluorescent lighting on all day because the daylight is insufficient. That is a lot more energy use than an average house, especially during daylight hours when many people are out and not at home. It means that solar PV is a great option for business, and large systems, where possible, will provide excellent returns.

Here is the table with the various rates depending on the size of system:

Just like with domestic properties, you will need a D rating or higher on your EPC to get the standard FiT rate. If your EPC is lower, you will only get the lower rate (shown in the table above). This is not applicable for wind turbines.

As you can see from the table, the rates go down appreciably with larger systems, but they are very large systems. You need about 4 panels to generate a kW of power, so anything over a 16 panel system is likely to fall in to the 4-10kW range. You would need 40 meter square panels to get up to a 10kW system, at a cost of around £15,000 or more, so chances are most business will fall into the 2 lower tiers, unless you have some serious roof space.

Does solar pv make sense for business?

Solar pays back within 8-10 years of installation, which usually falls within the period businesses would consider worthwhile. For some businesses who would use close to 100% of the energy generated (I.e. those with high base loads during daylight hours such as offices and shops), the payback may be even quicker. Unfortunately, the feed in tariff is paid over 20 years, for both residential properties and business – which most businesses don’t tend to budget for. There are plenty of businesses that will benefit however, so give us a call and see if it is worth getting solar pv for your business.

Think we missed something? Do you have a different opinion?

Comment below to get your voice heard…

Mr Chaggar from Ealing, London not only benefits from a well insulated home but he and his family can utilise renewable heating and electricity both produced on site. As the home is fairly new and has been insulated throughout, which means it requires less amount of energy to provide for the needs of the people residing there.

Mr Chagger used TheGreenAge’s partner Complete Plumbing Clean Energy (CPCE) to carry out the work on the heating and solar PV system. CPCE provide a high level of precision and engineering expertise to deliver projects of this type.

By combining electricity produced on site means that some of this energy is then used to power the compressor on the air source heat pump, there is little use for gas central in this instance.

The installation includes the following:

• Mitsubishi Ecodan air source heat pump
• Underfloor heating throughout the property
• 1kWp Bisol solar PV system
• High efficiency hot water tank

Grants and Subsidy benefits to the customer

• Renewable Heat Incentive (RHI) payments for producing renewable hot water on the air source heat pump;
• Feed-in Tariff payments for the electricity produced and exported by the solar PV system

While there is an upfront cost component to paying for the solar PV and the air source heat pump, because of the Government subsidies available, the cost should be recovered within the first 7-8 years on both systems. While there isn’t Green Deal Finance help on the air source heat pump (due to the RHI), customer can get help from this funding for a solar PV system.

To claim the RHI, and potentially get some funding from Green Deal Finance for solar PV, the customer has to have a Green Deal Assessment (carried out here by us, TheGreenAge) and have an MCS certificate produced by the installer (produced by CPCE).

UPDATE: The Feed-In Tariff is now closed for new applications. To find out about the new scheme designed to replace it, click here.

On the first of April 2014, the headline solar PV feed in tariff is reducing to 14.38p / kWh from 14.90p / kWh.

For an average 4 kW system (16 panels), this would reduce the annual return by about £20. On the face of it not much, but when you consider you receive the Feed-in tariff generation payment for the next 20 years, that equates to £400.

Remember the feed-in tariff payment is split into two parts; the first is the generation tariff, which pays you for every kWh of electricity you produce, regardless of whether this is used in the home or sold back to the gird – this is the part of the feed-in tariff that is reducing.

The Solar PV Export Tariff for 2014 / 15

The second part of the feed-in tariff is known as the export tariff, which pays you for every unit of electricity you export back to the electrical grid.

From the 1^st April 2014, the export tariff will be 4.77p / kWh.

So with the generation tariff reducing in just a month’s time, you need to act fast to lock in the higher solar PV feed-in tariff, guaranteed for the next 20 years.

If you would like to get your solar PV system installed before the April 1^st deadline call TheGreenAge now on 0208 144 0897, with prices starting from as little as £1650 per kW of panels installed.

[Update: As nuclear and coal stations are wound down in the UK, this could mean the death of the Economy 7 tariff. This would mean storage heaters becoming more expensive to run, and as such we no longer recommend people install new storage heaters. Read our latest advice here under ‘The future of storage heaters’.]

Do storage heaters still have a place in the home?

Read more

Economy 7 and storage heaters

To make the most of a storage heater, you need to be on an Economy 7 tariff. Unfortunately, a lot of people don’t know how to best utilise this and end up charging their heaters at the wrong time.

The easiest way to understand storage heaters is to visualise them as a big rechargeable battery; they require charging prior to discharging the energy contained within them. With Economy 7 tariffs, the electricity is supplied to your home at two rates: expensive ‘peak-time’ electricity and cheap ‘off-peak’ electricity. The cheapest way to ‘recharge’ the storage heater would be to do so using the cheap ‘off-peak’ electricity, but it just so happens that this is only available during the middle of the night – usually from 12 until 7 in the morning.

If you charge the storage heater during the middle of the day then you will be charged the peak rate and this quickly becomes a very expensive way to heat the home.

Will storage heaters leak heat?

Unlike a battery that will retain a lot of its charge until required, the storage heater will begin to leak heat almost immediately. Obviously the longer the storage heater can retain the heat, the more useful it is, and therefore companies will make you pay more for these products.

As a rule of thumb though, a storage heater will lose the majority of its stored heat over a 12 hour period. This means that if you get in from work at 7pm, the majority of useful heat will already have dissipated into the home – so the storage heater will not provide you with the temperature uplift you would expect from a traditional heating system.

Obviously this can be mitigated to a certain extent by having a really well insulated house, since the heat can’t escape the property. However any solid brick or uninsulated cavity wall home is going to struggle.

How to set up your storage heater controls

Most storage heaters have 2 key controls:

1. Power switches – this determines whether you are using off-peak on peak electricity to charge the storage heater (remember off-peak is considerably cheaper!)
2. Input and output controls – the input control determines how much electricity the storage heater will use to charge (and therefore the amount of available heat once the storage heater is charged). The output control controls the rate at which the storage heater emits heat into the room.

In terms of running the storage heaters in the most effective (and cheapest) manner possible, the first thing to ensure is that you don’t use the peak electricity power switch unless absolutely necessary – obviously you don’t want to get cold, but try to avoid using this unless in the middle of the winter when you need a heating boost. The idea is to make sure the storage heater only charges during off-peak hours.

Obviously turning the output control right up will mean that the storage heater does all its heating very early in the morning, so not ideal if you want to be warm in the evenings. If you do get a new storage heater it should retain the heat until mid/late afternoon – it is then that you should turn up the output, so the house warms for when you get home.

Make sure you turn the output to zero when you are not at home or when you go to bed – there is no point releasing the heat as the storage heater charges, since this means that it won’t have any ‘charge’ for when you need it – instead, it will function more as an electric radiator.

Solar PV and Storage Heaters

Some people ask if it is worth running their storage heaters from electricity generated by solar PV. The answer to this is actually not as straightforward as you would think.

Firstly, you generally use more heating during the winter, at a time when your panels are not producing as much electricity as in the summer. Storage heaters require a lot of electricity, and if you had them on all day during the winter, rather than at night, the additional peak rate grid electricity you would need to supplement the solar panels would be prohibitive, unless you had a really big 10kW+ system (40 panels).

Solar PV Optimisers and Storage Heaters

Having said that, there are ways you can make solar and storage heaters work for you. Technology like the Apollo Gem or the Optimmersion work by utilising all the leftover unused energy generated by your solar system that would otherwise go back to the grid.

Typically this is used to heat your water, but there is no reason why you cannot connect this up to your storage heaters. It won’t be enough to meet all your heating needs, and you will still need a charging cycle at night, but you could use it to top up your heating during the day, and ensure that you have some useful heat still left when you get home in the evening.

Installing storage heaters

Need new storage heaters? We have scoured the country for the best tradespeople, so that we can make sure we only recommend those we really trust.

If you would like us to find you a local installer for storage heaters, just fill in the form below and we will be in touch shortly!

I thought in this blog I would just briefly share a discussion I had with a lady on Tuesday, during a Green Deal Assessment. She was interested in solar, her electricity bills were really high and she was a stay at home mum, meaning energy usage was relatively even during over the course of the day.

Installing solar PV is great, since producing your own electricity means you don’t need to buy as much from the grid. The issue is that you would need a massive amount of solar panels and a battery storage system to produce ALL of your electricity and be able to use it at night when the sun doesn’t shine.

On the whole people tend to choose a grid tied solar system, because they are simple and if you need any additional electricity you can simply buy it from the grid. These systems cost about £6000 and for that you will get you a 3.5kW system, which if the sun shines an average amount during the year will produce about 2,900kWh of electricity per year.

If you could use every kWh of the electricity you produce, that would mean that on average you would be saving about £450 per year. That is great, but for the savings to pay back a £6000 system, it would take about 14 years which is not ideal!

The Solar Feed-in tariff

The solar feed-in tariff makes getting solar PV installed on your property economically worthwhile.

There are two parts to the feed-in tariff, the first is the one that gets all the press coverage – and is known as the Generation tariff. Currently that is set at 14.90p, which you get paid for every kWh your solar PV installation makes, regardless of whether you sell it back to the grid or you use it in the home, and this is guaranteed for 20 years.

So for a £6000, 3.5kW system you could get expect to get a quarterly cheque for £112 (just shy of £450 a year). Couple this with your energy bill saving and we this is starting to make financial sense!

The Export Tariff Bonus!

The final payment is known as the export tariff and this is a payment you get paid for every kWh you sell back to the grid. Unfortunately the price you get paid is about a third of the price you would need to pay your energy company for that same unit of electricity, but things aren’t all bad as we are about to see!

Solar PV systems are installed with a generation meter, which means that you can simply give the readings to the electricity company every quarter to get the exact payment for the electricity you generate. In most cases however, an export meter is not installed, so what the energy company will do is make the assumption that you export 50% of your energy. Now obviously if you are using 50% or more of the electricity you produce, you are still going to ‘export’ 50% in the energy companies eyes.

So in theory if you were to use 100% of the energy in your home, which would produce the maximum energy saving on your bill, you are also going to get a payment for exporting 50% of the energy (despite the fact in practise you don’t actually do it).

This is when the export tariff works in your favour, and until smart meters are rolled out, domestic solar installations will be installed with no mechanism for accurately reading how much energy you export.

What this actually means is that in a household that uses 80% plus of the electricity they produce, they are going to get this bonus payment.

I have done a worked example below:

3.5kW system produces 2900kWh of electricity per year, of which 90% of this is used in the home:

• Generation Tariff Payment – £432 (2900 x 14.9p x 100%)
• Energy saving – £391 (2900 x 15p x 90%)
• Export Tariff Payment – £66 (2900 x 4.55 x 50%*)

*That is payment for exporting 50% of the electricity however in reality you are only going to be export 10% of it.

Once I had explained this all to her – she simply said ‘well that’s a no brainer’. We agree – it really is and with the cheeky bonus export tariff payment offering potential returns of over £900 a year now really is a great time to take advantage of it. You may of read about the ‘end of cheap solar panels’ in a blog I wrote a couple of weeks ago, so don’t delay. If you are interested in finding out if solar may work for you, give us a ring on 0208 144 0897.

Have a great weekend and enjoy the sun!

Solar Prices are Getting Cheaper

In a world that seems to be getting more expensive on a daily basis it is refreshing to read that one of the great hopes for our future energy security is significantly reducing in price across the globe.

The following graph shows the price of crystalline silicon photovoltaic cells when they came onto the market in 1977 and how the price has decreased over ever since.

The rule of thumb for this decrease is that the cost to generate the photovoltaic cells falls by 20% with each doubling of global manufacturing capability.

Solar – A maturing market

The solar industry is a funny one, since only a few years ago installing solar panels on your roof was seen as somewhat of a luxury because they were prohibitively expensive and the financial payback was 15 – 20 years or more.

Then all of a sudden, the Chinese Government invested heavily in solar via the Chinese Development Bank, which provided very cheap debt to solar manufacturers as well as tax breaks and subsidies. In 2010 alone, $30bn was handed out to 5 solar companies in China, allowing them to expand their operations very rapidly, leading to a much higher manufacturing capacity.

This move by the Chinese effectively turned the whole industry on its head, but quickly resulted in supply vastly outstripping demand, resulting in solar cell prices tanking.

Now obviously this isn’t good news for the big solar manufacturing companies outside of China who are looking to make profits from the goods they are selling. Only a few weeks ago, Suntech, one of the world’s biggest solar panel manufacturers, defaulted on a $500m bond payment.

In fact, in an effort to slow the massive influx of Chinese manufactured solar panels, the EU has imposed anti-dumping duties on Chinese solar imports having found that they were selling them in Europe at 88% lower than cost. This tax import rate is currently set by the EU at 11.8%, however if China refuse to stop their solar panel dumping the rate will go up to 47.6% in August.

This unfortunately has created an issue for many UK based installers who get their panels directly from China, since they will no longer be able to import them so cheaply; a situation that could mark the end of the cheap home solar PV installation

 The Tanking solar Price is (currently) great for Consumers

Thus far, this fierce competition introduced by the influx of new Chinese solar companies has been great for consumers (driving down prices of solar panels), but if UK installers need to start paying almost 50% tax on the panels they import then their prices will need to increase accordingly.

It is currently possible to buy a 4kW system in the UK for approximately £7,000 – £8,000. A system this size should produce about 3,400kWh of electricity per year. If you were to use half of this yourself and sell half back to the grid you would make approximately £850 per year as per the calculations below.

Therefore the payback is less than 9 years, and then you will continue receiving the subsidies for the next 10/11 years (20 years after installation).

This is obviously the situation as it is today, but this could change in a matter of weeks – so act quickly to ensure you get the best deal on your solar panels. The Feed in tariff is also reviewed on a quarterly basis, so is likely to continue to fall over the coming years, so now is the perfect time to install a solar system.

Looking Forward to the Future

Despite the issues surrounding the cost of the panels resulting from the sudden increase in Chinese manufacturing capacity and the EUs decision to tax panels made there, the technology that goes into making the panels is improving on a seemingly daily basis.

Even last week, the Stanford Institute for Materials and Energy Sciences announced massive efficiency improvements (about a 100 fold increase) on a solar cell that can convert all solar wavelengths into electricity (current PV only uses the visible spectrum). Where heat negatively impacts traditional solar PV cells, this new technology performs substantially better in warm conditions.

I have written before that it will be a big day for solar when installed it can produce electricity at the same price as traditional fossil fuels (which is almost the case in California now) – known as grid parity. And hopefully one doesn’t have to look too far into the future to a time when grid parity could be reached in sunny UK too, there just might be a few speedbumps along the way!

Introduction to solar power plants

The majority of our power comes indirectly from the sun, but the challenge is to make use of solar energy directly and in a non-polluting fashion.  This is not a new idea; development of solar energy dates back more than 100 years, to the middle of the industrial revolution. In this section, we discuss solar PV and solar heating for the home, but there is also a lot of capital investment directed at producing electricity from solar on a commercial scale.

Types of solar power plant

There are two types of large scale solar power plants: the first type are photovoltaic power plants, the largest of which is situated in Canada and is the 97MW Sarnia PV power plant. There are currently eight PV plants, located mainly in Europe, that have a power outage of over 50MW, however there are eight plants planned for the USA that have received funding guarantees that are in excess of 150MW, and these are all due to be completed between 2013 and 2015. The largest planned installation is in China, and this will produce 2000MW at peak (as a reference point the largest nuclear power plant is rated at more than 7900MW)

The other type is the commercial concentrated solar power plants (CSP); these were first developed in the 1980s. The largest CSP is located in the Mojave Desert in California, known as SEGS CSP and has an output of 354MW. The majority of CSP plants are parabolic troughs (see below), and are located in Spain and the USA. Solar power plants provided Spain with 3% of its electricity in 2010, and with many more CSP plants in the pipeline this is sure to increase over the coming years.

How solar photovoltaic power plants work

The process of converting light (photons) to electricity (voltage) is called the solar photovoltaic (PV) effect. Photovoltaic solar power cells convert sunlight directly into solar power (electricity). They use a thin layer of semi-conducting material, usually silicone, encased between a sheet of glass and a polymer resin. When exposed to daylight electrons in the semi-conducting material become energised. These electrons are then able to flow through the material generating a direct current (DC). These are also used for residential needs on a smaller scale, and are discussed in more detail here.

How concentrated solar power plants work

CSP power plants do not convert sunlight directly into electricity, instead they use lenses and mirrors and tracking systems to focus a large area of sunlight into a small beam, which is then used as the heat source much like in a conventional power station. There are a few types of CSP power station but all use the same principal of heating the working fluid by direct sunlight.

Parabolic trough solar power system

In the case of the parabolic trough system, the sun’s energy is concentrated by parabolically curved, trough-shaped reflectors onto a receiver pipe running along the inside of the curved surface. This energy heats working fluid flowing through the pipe, and the heat energy is then used to generate electricity in a conventional steam generator.A collector field comprises many troughs in parallel rows aligned on a north-south axis.

Power tower solar power system

A power tower converts sunshine into clean electricity for the world’s electricity grids. The technology utilises many large, sun-tracking mirrors (heliostats) to focus sunlight on a receiver at the top of a tower. A heat transfer fluid heated in the receiver is used to generate steam, which in turn is used in a conventional turbine-generator to produce electricity.

Early power towers (such as the Solar One plant) utilise steam as the heat transfer fluid; current US designs (including Solar Two, pictured) utilise molten nitrate salt because of its superior heat transfer and energy storage capabilities. Current European designs use air as the heat transfer medium because of its high temperature and its ease of use.

Parabolic dish solar power system

Parabolic dish systems consist of a parabolic-shaped point focus concentrator in the form of a dish that reflects solar radiation onto a receiver mounted at the focal point. These concentrators are mounted on a structure with a two-axis tracking system to follow the sun. The collected heat is typically utilized directly by a heat engine mounted on the receiver moving with the dish structure.

Solar power and the UK industry

Producing electricity on a mass scale in the UK does is not currently as commercially viable as wind power or hydroelectricity, although small scale community projects do exist. For example the Westmill Solar Plant, built in 2011, has one of the largest number of arrays, situated between Oxford and Swindon. Although the level of Feed-in Tariff support was cut for small scale producers, twice this year, ROC support still remains at two certificates per mWh of electricity produced for generators of over 5MW. In addition, the UK remains one of the leading nations in terms of providing solar power engineering expertise and solar energy services round the world and will continue to do so over the next few years.

What is solar PV?

The process of converting light (photons) to electricity (voltage) is called the solar photovoltaic (PV) effect. Photovoltaic solar cells convert sunlight directly into solar power (electricity). They use thin layers of semi-conducting material that is charged differently between the top and bottom layers. The semi-conducting material can be encased between a sheet of glass and/or a polymer resin.

When exposed to daylight, electrons in the semi-conducting material absorb the photons, causing them to become highly energised. These move between the top and bottom surfaces of the semi-conducting material. This movement of electrons generates a current known as a direct current (DC). This is then fed through an inverter, which converts the power to alternating current (AC) for use in your home.

Types of solar panel

Different types of solar PV installations require slightly different components. However in the next two sections we have explained in detail all the main components that will make up your solar PV array and provide you with 100% renewable, free electricity.

The solar panel is the key component of any solar photovoltaic system, which takes the sun’s energy and converts it into an electrical current. There are three main types of solar panel (as well as the hybrid version) currently in commercial production, all of which are based on silicon semiconductors:

Monocrystalline solar cells

This type of solar cell is made from thin wafers of silicon cut from artificially-grown crystals. These cells are created from single crystals grown in isolation, making them the most expensive of the three varieties (approximately 35% more expensive than equivalent polycrystalline cells), but they have the highest efficiency rating – between 15-24%.

Polycrystalline solar cells

This type of solar cell is also made from thin wafers of silicon cut from artificially grown crystals, but instead of single crystals, these cells are made from multiple interlocking silicon crystals grown together. This makes them cheaper to produce, but their efficiency is lower than the monocrystalline solar cells, currently at 13-18%

Amorphous solar cells

These are the cheapest type of solar cell to produce, are relatively new to the market and are produced very differently to the two other types. Instead of using crystals, silicon is deposited very thinly on a backing substrate.

There are two real benefits of the amorphous solar cell; firstly the layer of silicon is so thin it allows the solar cells to be flexible, and secondly they are more efficient in low light levels (like during winter).

This, however, comes at a price; they have the lowest efficiency rating of all three types – approximately 7% – 9%, requiring approximately double the panel area to produce the same output. In addition, as this is a relatively new science, there is no agreed industry-wide production technique, so they are not as robust as the other two types.

Hybrid solar cells

This is not a type of solar cell in its own right; instead it is a combination of both amorphous solar cells and monocrystalline solar cells. These are known as HIT solar cells (Heterojunction with Intrinsic Thin Layer – a bit of a mouthful!), and have higher efficiency ratings than any of the other three types of solar cell alone. In addition, they are also better suited in sunnier climes, where temperatures often exceed 25⁰C, creating up to 10% more electricity.

We think in many cases polycrystalline cells are the most suitable option, as they provide value for money while still also being relatively efficient.

Future solar technologies

• Research is currently underway to develop almost 100% transparent solar glass, which can be used in building applications. Organic polymer photovoltaics will be ultra-thin and more efficient than existing types, and could see windows transformed into electricity generators!
• Perovskite is a new type of solar cell which is more efficient than current types on the market. The technology is currently in refinement, as it has a number of flaws which would need to be resolved before it could be mass-produced.

Solar PV inverters

All the electricity produced by the solar panels is produced as direct current (DC), which differs from the electricity that is distributed through the grid and we use in our homes, which is alternating current (AC). For this reason most solar photovoltaic systems are now connected up with some type of inverter, which changes the DC to AC, allowing the individual to sell the electricity back to the grid (in grid-tied systems) or to be used easily in homes.

There are 2 major types of inverter that can be installed in your solar photovoltaic system:

1. String inverters (also known as central inverters)

These are used in grid-tied systems where the solar panels are wired together in series, which is known as a string of panels. Each string of panels is connected to a string inverter, which converts the DC current to AC for use in the home and selling back to the grid. You can imagine each string as a mini power station, producing electricity.

The main issue with string inverters is that if one of the panels in the string fails or produces less electricity (from things like shading), this impacts the output of all the panels. They will all operate at the output of the worst panel, so a small amount of shading or debris on your solar array can disproportionally reduce the total output of your entire solar photovoltaic system.

They also have relatively short lifespans when compared to micro inverters.

The benefits include simple wiring and that you can use thinner wires within your solar PV system, so less copper is used which makes the system cheaper. Buying one string inverter (which is normally the case of most home solar PV systems) is also considerably cheaper than buying multiple micro inverters.

2. Micro inverters

These are a newer technology and service each solar panel individually, so each panel requires its own micro inverter and acts as an individual power station.  As a result, micro inverters do not suffer the same performance reduction as a result of shading because any power reduction in a particular solar panel is handled by one micro inverter, having little effect on the combined power output from the entire solar photovoltaic system.

Micro inverters are much more expensive than the string inverters. However much of this cost is offset by the increased performance (25% more power produced using micro inverters) and the fact that they are more reliable than string inverters (warranties for micro inverters are up to 25 years).

Buying inverters for your solar PV system

When looking for which inverters to buy, ideally you want your alternating current (AC) to match that provided by the utility companies. Waveform relates to the quality of the AC signal that an inverter produces. Cheaper inverters will provide modified sine wave signal, while the more expensive versions will produce the pure sine wave signal. Some appliances (such as computers) simply don’t work unless they are powered by a pure sine wave signal, so we recommend strongly that you spend a little more to get this type of inverter.

Grid tie inverters differ slightly from your regular inverters in that the AC pure sine wave signal has to be perfectly coordinated with the waveform from the grid. As such, these tend to be more expensive than the typical inverters that you buy. They also have a built-in safety feature to cut off power from the solar array if the electricity grid goes down for any reason.

It is also worth noting that most inverters now also have ‘Maximum Power Point Tracking’ (known as MPPT) installed within them, which helps to maximise the electrical output of your solar photovoltaic array system.

The principle of MPPT is to extract the maximum available power from the photovoltaic module by making them operate at the most efficient voltage (known as the maximum power point voltage). The algorithm included in the MPPT inverter compares the output from the photovoltaic module with grid voltage and then fixes it at the most efficient voltage, to allow you to export the maximum amount of kWh of electricity back to the grid. An MPPT charger in your solar photovoltaic system will improve your power gain by 20-45% in the winter and 10-15% in the summer.

Benefits

• All solar PV panels are rapidly decreasing in price due to better production techniques and increased competition between manufacturers and suppliers.
• Monocrystalline solar PV cells are the most efficient type of solar PV cell (rated between 15-24%), so smaller panels can produce equivalent amounts of electricity compared to other solar cell types.
• Polycrystalline solar PV cells are easier to produce than the monocrystalline solar PV cells and therefore cheaper to buy, still providing decent efficiency levels (13-18%).
• Amorphous solar PV cells are the easiest to produce and as the silicon is deposited on any surface, these panels can be made into any shape.
• Hybrid solar PV combine amorphous and monocrystalline cells giving you the advantages of both of these two types of solar cell.

Limitations

• Polycrystalline and amorphous solar PV cells are less efficient than monocrystalline, and therefore bigger panels are needed to produce the equivalent electricity output.
• The technique for building monocrystalline solar cells is more difficult and this is reflected in the higher price of this type of panel.

The battery

One of the major issues with solar PV systems is that they only produce electricity when the sun is shining. If you are looking to go ‘off-grid’ or have battery back up in times of grid blackouts, you will need batteries within your solar PV system.

In these systems, electricity produced from the solar cells is either used in the home as required, or if there is no demand in the home, it is converted to chemical energy in the form of batteries. These batteries can then produce the electicrity at night to allow you to use your solar PV system ’24/7′.

The electricity produced by your solar system is stored in deep-cycle lead acid batteries that look very similar to the ones found in most cars today (although structurally different). The two most popular types of battery are GEL and Absorbed Glass Mat (AGM), which store the charge very well and do not degrade nearly as fast as the common lead acid (wet cell) battery. Both types of batteries are designed to gradually discharge slowly and recharge 80% of their capacity a multiple number of times.

An automotive battery is a shallow-cycle battery, and this is designed to discharge only about 20% of its electricity so is unsuitable for solar photovoltaic set-up. The reason being is that if any more than 20% is drawn more than a few dozen times, it will get damaged and no longer take charge.

Solar photovoltaic batteries tend to operate at 12 volts, and can be arranged in banks (multiple batteries), increasing the storage potential of your solar photovoltaic set up. A bank of batteries organised in a series increases the capacity of your storage but also increases the voltage delivered from your bank, while multiple batteries organised in a parallel circuit increase the capacity, but keep the voltage the same (mains electricity runs at higher voltage, so if you have a grid tie system it is likely you will try to match this by running the batteries in series).

Solar Charge Controllers

Solar Charge Controllers (also known as Solar Charge Regulators) are used in solar photovoltaic systems to prevent the batteries from being overcharged. If you decide to implement a ‘grid-tied’ system, a solar charge controller is not necessary, as any excess electricity that you don’t use at any particular moment is sold directly back to the grid.

However, for any of the other three setups, a charge controller is necessary; it acts to regulate the flow of electricity between the solar photovoltaic modules, the batteries and your appliances (known as the load).

When the load is drawing power (e.g. you are watching television), the charge controller allows electricity to flow from the solar panels directly (if the sun is shining), or from the battery, or from a mixture of the two. The charge controller also prevents damage to the battery by monitoring the flow of electricity in and out. For instance if your system overcharges the battery, it will damage them. The same is also true if you completely discharge all the charge held within the battery.

At night, when the solar units are no longer producing electricity, the solar charge controller prevents reverse current flowing from the batteries back into the solar panels.

Solar charge controllers also are equipped with highly effective charging programs that maximise the charging speed, while still preventing overcharging.

Most are also equipped with maximum power point (MPPT) charging. The principle of MPPT is to extract the maximum available power from the photovoltaic module by making them operate at the most efficient voltage (known as the maximum power point voltage). The algorithm included in the MPPT solar charge controller compares the output from the photovoltaic module with the battery voltage and then fixes it at the best charging voltage, to get the maximum charge into the battery. The maximum power produced by the solar photovoltaic module is dependent on the amount of sun hitting the solar cells and the temperature of the cells. Incorporating a MPPT charger into your solar photovoltaic system will improve your power gain by 20-45% in the winter and 10-15% in the summer.

Solar array mounting

As discussed earlier, the amount of power that your solar photovoltaic system produces is dependent on the intensity of light hitting your solar array. There are three types of mounting you can get for your solar panels to help maximise the amount of light that they receive.

Fixed solar array mountings

These are the simplest of all the mounting systems, and also the cheapest. In this system, the solar panels will not move at all at any time during the year, so you want to ensure that when you put in the panels they are facing the equator to maximise sunlight.

Manually adjustable solar mountings

These can be changed a few times a year to adjust for the winter and summer sun. The sun is highest in the sky during the summer months and lower in the winter, so by being able to adjust the angle of your solar array ensures that the sunlight hits the array at the best angle to avoid reflection.

Fully automated tracking solar mount

These mountings track the sun, to ensure that at all times the angle of the solar array is maximising sunlight. These are certainly the most expensive type as they are constantly moving, but they are also by far the most efficient. Despite this, it has been proven to be more cost effective to add an extra solar panel to your array and use the fixed or adjustable mountings.

Installing Solar PV

Are you thinking about installing a solar PV system at home? We have scoured the country for the best tradespeople, so that we can make sure we only recommend those we really trust.

If you would like us to find you a local installer to help install a solar PV system in your home, just fill in the form below and we will be in touch shortly!

Each solar setup has its own benefits and limitations, and it is important to gain a real understanding of these before you invest in a potentially expensive solar PV system, to help avoid disappointment further down the line.

Grid-tied solar PV Systems

99% of solar systems installed on people’s homes in the UK are what’s known as ‘grid-tied’ systems. These grid-tied systems allow you to use the free electricity you create from the solar PV system, as well as electricity from the National Grid. This gives you flexibility, since you have a constant supply of electricity, whether or not the sun is shining.

Any shortfall in supply from your solar PV array can be met by additional electricity supplied via the grid, but there is also the added benefit of being able to sell any surplus back to the grid. In essence, a grid-tied system will go some way to reducing your dependence on the utility companies, and also save you money, while still giving you the comfort of as much electricity as you need from the grid. The lack of batteries also makes this type of solar setup cheaper to install.

Grid-tied solar PV installations have become incredibly popular in the UK recently due to generous government subsidies (guaranteed for 25 years from the date of installation).

Solar PV home battery storage

Read more

Off-grid/standalone solar PV systems

Producing 100% of your own electricity in a clean and sustainable manner is the dream scenario for many people; the thought of never paying another electricity bill, and never suffering from grid blackouts is obviously a very attractive proposition.

However, an off-grid system does not need to be very sophisticated and grand in scale – it can simply power a light in your garden shed, or a water fountain in your garden. For this reason, off-grid installations are the most common type of solar installation across the globe, providing electricity to any isolated location (normally where no other electricity source is readily available).

The disadvantage is that you essentially become the utility company, so any costly repairs fall under your remit. Also, if there is a problem with your supply for any reason, you will not have electricity. Solar power is also an intermittent source (i.e it doesn’t power 100% of the time), so if you need electricity during the night (for lighting etc), you will need to install batteries within your system. These enable you to store energy during the day and use it when you are not generating.

The rewards for installing an off-grid system are clear; however the increased responsibility of owning your home’s electricity supply could make this kind of system a potentially daunting task for solar PV beginners.

Grid-tied with battery backup systems

The issue with this system is its added complexity compared to the grid-tied solar PV system described above. The batteries will require additional maintenance and add significantly to the final cost, and they will also introduce additional inefficiencies within your system – potentially a 15% loss in overall performance.

Grid fallback systems

This is where electricity is taken from the batteries and run through an inverter to provide the electricity required in the home. Once the batteries begin to go flat, the system automatically switches over to grid power, allowing the solar panels to once again charge the bank of batteries, and the process starts again.

Installing Solar PV

Are you thinking about installing a solar PV system at home? We have scoured the country for the best tradespeople, so that we can make sure we only recommend those we really trust.

If you would like us to find you a local installer to help install a solar PV system in your home, just fill in the form below and we will be in touch shortly!