An Introduction to Gas Boilers


Gas boilers are central heating systems that act like mini fires, continuously heating water. This heated water is then pumped around the property through pipes and radiators in order to heat space, and either pumped directly to taps and showers (as with a combi boiler), or stored in a hot water tank for future water usage. The boiler uses either on-grid gas or bulk LPG stored on site. This gas is then burned in the boiler’s combustion chamber and warms the water to around 70°C through a heat exchanger.

Are gas boilers dangerous?

Importantly, when natural gas is burned without enough oxygen it burns yellow. This creates a dangerous toxic gas called carbon monoxide, which can be lethal if inhaled for long periods. You shouldn’t have any problems, provided you have a carbon monoxide detector and have your boiler serviced regularly.

Are there different types of boiler available?

There are four main types of gas boiler that are installed up and down the UK:

Combination, or combi boilers do not use a water tank to store the hot water but produce instant hot water direct from the boiler for taps and showers.

System boilers store hot water in an insulated water tank and have one cold water tank.

Regular boilers in essence work in much the same way as system boilers, but can be vented (one cold water tank) or unvented (two cold water tanks).

Combined heat and power (CHP) boilers act as micro power plants by providing your hot water like the previous three, but also generating electricity to use around the home.

>>> The cost of heating your home with gas vs electricity <<<

Are gas boilers efficient?

We recommend replacing your boiler every 12 years or so: this is to compensate for both the loss of efficiency and the lack of available spare parts for repair. If your boiler is pre-2002 the chances are that it is a non-condensing model, which are up to 80% efficient, with new condensing models reaching into the 90s%.

Boiler controls

Gas boilers can be programmed to come on at specific times of the day, to ensure that you never heat your home pointlessly when no one is in. Also, to avoid overheating or under-heating your property, thermostats can be installed to make sure that the required temperature is reached and maintained. For larger properties with rooms that are often uninhabited, thermostatic radiator valves may be installed on each radiator to minimise wasted heat.

Installing a new boiler

Are you thinking about getting a new boiler? 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 install a new boiler in your home, just fill in the form below and we will be in touch shortly!

    Waste Water Heat Recovery Systems


What is a WWHRS and how does it work?

Typically, a waste water heat recovery system works by extracting the heat from the water your shower or bath sends down the drain. This heat is used to warm the incoming mains water, reducing the strain on your boiler and the energy required to heat your water up to temperature. A system normally takes the form of a long vertical copper pipe, where the warm water runs alongside the colder mains water to exchange the heat.

The devices are typically around 60% efficient, so they convert 60% of the potential energy in the waste water back into heat for the incoming water. This can save you money on your bills, especially if you use a lot of hot water in your home. The payback period – as we will discuss – is another matter.

The good news is that it is a fairly simple device. It has no electrical components, no pumps or controllers, and so it requires very little maintenance. It has an expected lifespan of 20 years+. Unfortunately they are usually a little too expensive for the payback they generate in domestic dwellings, but this is beginning to change.

Is it worth retrofitting a WWHRS?

In some cases retrofitting may be possible, but the bulk and length of the recovery device means that most showers or baths wouldn’t be suitable. It is much easier to get it installed when you are fitting a new bathroom.

How much do they cost?

They typically start at around £600 + installation. So you are looking at over a £1,000 to get a unit in your home.

Are they worth it?

Until 2015, installers often used WWHRSs as a means to get a new home up to Sustainable Homes Code standards, rather than a means to save money. Now that the Sustainable Homes Code is no longer around, although you certainly will save some cash with a WWHRS, the payback period is not worthwhile for most people.

A typical saving on an average home might be £20-30 a year. So the payback time is around 40 years typically. Of course, if you use a lot of hot water, it can begin to look a bit more attractive.

Other ways to recover wasted heat

There really are better ways to cut your bills – reducing your hot water use is a great way to cut your bills. That means less time in the shower, fewer baths and using a dishwasher instead of washing up under running hot water. Doing fewer hot washes in your washing machine will also cut your energy use. This is a much better way to save £20 a year, instead of installing an expensive appliance like this.




    Flue Gas Heat Recovery Systems


How do flue gas heat recovery systems work?

Flue Gas Heat Recovery Systems (FGHRS) take advantage of heat within waste flue gases resulting from the combustion of gas in your boiler. This recovered heat is used to preheat the cold water entering the boiler, thereby lowering the amount of energy needed to warm the water up to the required level.

Even the most efficient boilers available on the market today are only 90% efficient, as a result of heat lost in the waste flue gas, however the installation of a FGHRS on even a brand new boiler can help further drive up energy efficiency, helping you save money on your energy bills.

Flue gas heat recovery systems requires very little maintenance, with no need for mains electricity. They can they be used in combination with a number of renewable technologies and help cut water use by your boiler by up to 6%, which is helpful if you are on a water meter.

What can a flue gas heat recovery system do for my boiler?

Almost all modern boilers are ‘condensing boilers’. This means that they already have some sort of heat recovery type system built in, making them much more efficient than older boilers. Even so, a FGHRS can further increase the efficiency of these condensing boilers in most cases, delivering the same amount of heat with 7% less gas.

On older boilers the savings are much more substantial – for example, if you install a FGHRS on a G rated boiler you could see gas savings of up to 52%, whilst on older combis the savings can be up to 35%. In many cases, even though these savings are huge, it is probably a more economical decision to upgrade the boiler to a condensing model as well as installing a FGHRS.

Remember that not all boilers work with FGHRS and each system will be different, so you will need to check with the manufacturer to ensure your boiler is compatible.

A typical saving on an A band boiler would be around 5% on your gas bill, and we have done some worked examples to see what that would mean in terms of payback:

Modern A Band Boiler (5% saving)

Gas Usage Cost Savings through FGHRS Payback
10,000kWh (Small property) 400£/year £20 39 Years
20,000kWh (Medium sized property) 800£/year £40 20 Years
30,000kWh (Large Property) 1,200£/yr £60 13 Years

80% Efficient boiler (10% saving)

Gas Usage Cost Savings through FGHRS Payback
10,000kWh (Small property) 400£/year £40 20 Years
20,000kWh (Medium sized property) 800£/year £80 10 Years
30,000kWh (Large Property) 1,200£/yr £120 7 Years

As you can see, even without the GDHIF, it is a great addition to your boiler if you live in a large property.




    Introduction to heating controls


What are heating controls?

Heating controls allow you to easily regulate the temperature of your home. The controls automatically turn the heating on and off based on settings input by the user, to ensure maximum comfort. This process moves away from a fixed, traditional timer system and can therefore be used to better control the temperature within your home.

Thermostats, allowing people to control the temperature of their home, have been around for a long time. Newer heating control systems have evolved to the give residents total control of their heating, and by extension, their bills. The latest technology allows you to automatically control your heating to work around your daily schedule.

Products that make up a heating control system

There are four products that normally make up a full heating control system (based on a home with a traditional central heating system):

  1. A room thermostat
  2. A boiler programmer
  3. A hot water cylinder thermostat
  4. Thermostatic radiator valves

In our experience, many homes currently only have one or two of these.

Room thermostat

Room thermostats take the temperature of the ambient air in the home and feed it back to the boiler to tell it to either fire up to raise the temperature of the home, or to turn off since the home is warm enough and no additional heating is required.

They require free-flowing air so that the sensor can work out the right temperature. You’ll need to ensure that the thermostats are not blocked by household objects like curtains or furniture and avoid placing them near heat-emitting objects (fireplaces, radiators, household appliances etc). It is also recommended to house these in the lounge, since this is where homeowners typically spend most of their time. Having your thermostat in the hallway by your front door, for example, will not give an accurate reflection of the temperature of your home. This is because it’s an area commonly affected by draughts, when the front door is opened and closed.

Boiler programmers

Boiler ProgrammerA boiler programmer is an automated way of turning the boiler on and off. People tend to like their homes to be warm when they wake up or come home from work. There seems little point in heating the home when no-one is there to get the benefit from the heat. A programmer allows you to set very specific time frames for when the heating comes on from day to day.

Let’s take the example of a family that go to school/work during the day. Typically the boiler would come on at approximately 6-7am to heat the house ready for when the family wakes up. This would then go off at about 9 when the people in the home leave for work or school. The boiler could then fire up again about 4pm in preparation for everyone coming home and go off just before everyone goes to bed.

These programmers allow you to set different heating patterns for each day, so if at the weekend more time is spent at home, you could use the programmer to reflect that.

The hot water cylinder thermostat

Boiler thermostat

If you have an older boiler with a hot water tank, a hot water cylinder thermostat is a great way of ensuring the temperature of the water in the tank doesn’t get unnecessarily warm. Storing water at very high temperatures increases your bills, since you need to use more gas (or electricity if you use the immersion heater) to heat it. In addition, unless you’re a fan of a scalding hot shower or bath, you tend to add cold water to wash comfortably, which means you don’t need your water to be boiling in the first place.

The hot water cylinder thermostat is strapped to the hot water tank and has a dial on the front where you can adjust the temperature. Normally this temperature is set between 60 and 650c, which is hot enough to kill any bacteria but not so hot as to scold you when it comes out of the tap. It is a important to check the temperature of the thermostat on your hot water cylinder, since if it is set any higher than 650c, the chances are that you can turn it down and still get nice warm water, but save a bit on your gas bill at the same time.

If you don’t have a thermostat on your hot water cylinder it is certainly worth getting one fitted, since they cost less than £20 and can really help you to use less gas, but we do recommend getting a trained plumber to fit the thermostat.

Thermostatic radiator valves

TRVUsing programmers and thermostats you can, in theory, dictate when you want the heating to come on and the temperature that you want it to be. Thermostatic radiator valves (TRVs) allow you additional control to further fine-tune your heating system.

Much like the main thermostat, these TRVs track the temperature of the room in which the radiator is situated and will turn the radiator down (or off altogether) once it reaches the temperature chosen by you. TRVs allow the temperature of each room to be controlled individually from one another.

TRVs therefore really allow you to fine tune your heating system. For example, a room may have a lot of glazing and get warmer than the rest of your home when the sun is out. In this case, the thermostatic valve can shut off just that radiator, ensuring the occupant maximum comfort.

The future: intelligent heating systems

Heating optimisation works through an intelligent system that can help to save consumers additional money on their energy bills. Most people set their heating to come on at least an hour before they need it (in the mornings and evenings), but an intelligent heating system can sense the time it will take to heat the household to the required temperature, and turn heaters on automatically.

For example, a household might get up at 7am and want their home to be warm for this time. The traditional timer turns the heating on at 6am and works for an hour before everyone gets up. However on warmer days, the warmup time may be shorter than on cold days. An intelligent heating system will take this into consideration and set your boiler to fire up later, meaning less fuel will be used, resulting in savings in energy bills.

You might have a standard programmer that at most allows you to turn your heating on or off two or three times per day. An intelligent heating system can set multiple points where you set the time and temperature requirements for that day. The idea being that one may have different heating requirements for each day of the week.

Certain products on the market can have over 20 built-in plans, with further programmes available for customisation to an individual’s personal needs. For example, if you are a flexible worker, you can set customised patterns to suit your needs on different days. When you go on holiday, you can programme your heating not to come for the time you’re away.

In addition, these intelligent heating systems can be linked wirelessly to your phone or computer, so you can set the heating to come on as you are beginning your commute home. If you go away in cold weather, you can bring the heating on in your home even if you are not there to help prevent freezing.

Many of the intelligent heating features discussed above are now built into new heating control products available on the market today, and over the next few years they will become far more commonplace. All of the features work to more effectively regulate the temperature of your home, helping to minimise the amount of gas and electricity required to heat it.

The importance of heating controls

Installing huge quantities of loft or wall insulation will increase the energy efficiency of your property. However to get the biggest savings on your energy bills, it is absolutely key to be able to regulate the temperature of your home. Thermostats and TRVs are a really important way to help benefit from the increased energy efficiency of the envelope (floor, walls and roof) of your home. If you don’t have them, your boiler will continue to operate as it always has, which means your home will be warmer, but you will be using the same amount of gas.

It is also worth remembering that most of the features discussed will run behind the scenes in your home, so once you have set them up, you can then forget about them.

Finally – and this is one of our favourite tips – turning your thermostat just one degree can cut your energy bills by as much as 10%!




    Introduction to Hot Water Cylinders


There are two types of hot water cylinders found in homes today. The newer pressurised unvented hot water tanks and the older style vented hot water tanks.

Unvented hot water cylinders

Unvented hot water cylinders were only made legal in the UK in 1986, but have since grown rapidly in popularity. In an unvented system there is no cold water tank – instead, the sealed hot water cylinder is fed directly by the cold water mains. Since they are operating at mains pressure, they offer much better flow rates, meaning your shower and bath performance should be higher.

The other major benefit is that you don’t need to maintain a cold water tank in the loft (which vented systems require). This is good news since not only does it free up space, it also removes the potential freezing issue during our long cold winter periods.

In addition, since you aren’t relying on gravity to move the hot water around the home, the unvented cylinder can be located pretty much anywhere in your property.

Other advantages of installing an unvented system include reduced noise in the system (since there is no cold water filling of the water storage cistern), and since there is no water storage cistern and the system is essentially sealed, the cold water is not at risk from contamination.

Unvented water cylinders and the water expansion issue

Since water increases in volume as it gets warm, unvented cylinders need to include a mechanism that allows the expansion to take place, thereby keeping the cylinders operating at a safe pressure.

There are two methods of allowing this expansion to take place safely. The first is the bubble top unit, which uses an internal air bubble that is produced and trapped at the top of the cylinder when it is installed. The other type is the external expansion unit that utilises an expansion vessel to contain the expanded hot water.

The major issue with unvented hot water cylinders is that since hot water flow depends on the cold water main pressure; if for any reason the mains water is turned off, your home will be without access to any hot water.

Since unvented hot water tanks operate at higher pressure than vented systems and have additional safety features installed, these cylinders need to be installed by boiler specialists who hold a qualification that complies with G3 of building regulations. This means they tend to be far more expensive to install than traditional vented hot water systems.

Vented hot water systems

Vented hot water tanks are still the most common type of hot water system found in the UK. Unlike newer unvented tanks, these copper tanks are fed by cold water from a header tank (normally located in the loft) and they use gravity to drive the hot water around the home. A vent pipe links the vented hot water cylinder and the cold water in the header tank.

As with the unvented system, expansion of warm water is still an issue, but in this case the expansion simply takes place via the vent pipe and in the header tank.

The hot water pressure tends to be governed by the height of the water tank above the tap or shower feed. This means that although on the ground floor of the home the pressure might be excellent, in rooms on upper floors the pressure will be lower. As a result, many showers in homes with vented hot water tanks use electric pumps to drive the hot water to the shower at increased pressure.

Vented hot water cylinders are far less complicated than the pressurised vented systems and for this reason they are much simpler to maintain and install. This makes them a far cheaper option when compared to the unvented system.

Indirect systems

Most hot water cylinders are heated via an external heat source such as a gas boiler or solar thermal. In this case the hot water is heated and then travels through a copper coil in the hot water tank. The heat is then transferred from the from the external heat source to the water inside the hot water tank.

Indirect cylinders tend to be fitted with a direct backup (such as a immersion heater). Even if the boiler is broken, you can still produce hot water as and when you need it.

You can get both vented and unvented indirect systems.

Direct systems

In a direct cylinder system, the hot water is heated directly by an internal element such as an immersion heater. The hot water tends to be more expensive to produce in direct systems. Some homes have no access to gas, for example a mid-level flat. In this case they are forced to go with a direct system for their hot water, so they may choose to take advantage of Economy 7, which will give them a cheaper electricity at night to heat the hot water with.

Normally this type of cylinder would be fitted with two different immersion heaters, one for the peak electricity and one for the off-peak electricity. If this is the case, you really need to make sure that the immersion heaters are set up on the timers correctly to ensure you are paying the least possible for the hot water. There is no point heating water via your peak immersion heater during the middle of the night.

You can get both vented and unvented direct systems.

Combi boilers

We have covered combi boilers in more detail here, however it is worth mentioning that they can produce hot water for your home without the need for a hot water cylinder. While you can use electric point of use hot water heaters, gas currently is about ¼ of the price of electricity. Therefore it makes sense to use gas to heat the water as well as to carry out your heating.

The issue with combi boilers is that since they operate at mains water pressure, as soon as there is a pressure drop (i.e. more than one tap is opened in the home) then the hot water pressure is split between the two outlets. They are however ideal for smaller properties since there is no need to store hot water which is not very energy efficient.

>>> Should I replace my conventional boiler with a combi? <<<

Installing an unvented hot water cylinder

Are you interested in getting an unvented water cylinder? We have scoured the country for the best plumbers and heating engineers, so that we can make sure we only recommend those we really trust.

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

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      Regular Boiler


    What is a regular boiler?

    Regular boilers are the simplest types of boiler and in the past have been installed in the majority of homes in the UK. They create both the hot water required for your central heating system and the hot water that comes out of your taps.

    A regular boiler will always require a hot water tank

    A regular boiler will always require a hot water tank and may also require a cold water header tank in the loft, depending on whether you are operating a vented or unvented hot water cylinder system.

    Basically though, unvented hot water systems (also known as sealed systems) operate under mains pressure, and take advantage of a bubble of air in the cylinder or a separate expansion vessel to allow expansion of the hot water. For this reason no cold water header tank is necessary.

    Vented hot water systems also require a cold water tank

    Conversely, in a vented hot water system, the hot water uses the vent pipe for expansion (which connects the hot water tank and the cold water header tank); therefore it requires a cold water tank in the roof.

    Advantages of regular boilers

    Since regular boilers are the most basic type of boiler, they are reliable and cheaper to install than other types.

    The other major benefit of having a hot water tank in your heating system is that you can pull hot water from multiple sources at the same time without any loss of pressure, since you have a large store of readily-created hot water.

    In addition, most hot water tanks have electric immersion heaters associated with them so you can still get hot water even if your indirect hot water source (i.e. the hot water from the regular boiler) stops entering the hot water tank. This is obviously a benefit over combi boilers, which if broken will not be able to create any hot water at all.

    Limitations of regular boilers

    Since you are always required to install a hot water tank (and may also need to install a cold water tank, depending on the hot water cylinder type) when you install a regular boiler, they take up far more space than a combi boiler. This means they may not be suitable for particularly small properties.

    Another issue with having a hot water tank cylinder is that as soon as you use all the hot water, then the boiler (indirect heating system) or immersion heater (direct heating system) will need to be switched on to replenish the water.

    The final issue is that since you are storing hot water, there will obviously be heat lost from the hot water cylinder. Conversely combi boilers create hot water on demand, so there are no heat loss issues with these.

    Condensing regular boiler

    As with the other types of boiler, any open vent boiler bought today will be a condensing open vent boiler, and will capture the latent heat in the exhaust fumes of the boiler with a heat exchanger, so less fuel is used to produce the same amount of heat.

    Regular boilers with solar thermal

    Like system boilers, regular boilers are also compatible with solar thermal solutions. By creating hot water using the sun’s rays, you can take advantage of the RHI scheme.

    Depending on its age, replacing an old boiler with a new equivalent system should result in large savings to your energy bills. This is not only a result of the condensing element of the regular boiler, but also of the technical advances that have led to increased fuel efficiency, meaning more of the fuel is converted to useful heat in the boiler.




    Installing a new boiler

    Are you thinking about getting a new boiler? 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 install a new boiler in your home, just fill in the form below and we will be in touch shortly!


      Combi Boilers


    What is a combi boiler?

    A combi boiler combines a highly efficient water heater and a central heating boiler into one compact unit. As a result, the combi boiler is fast becoming the heating system of choice in new homes across the UK, comprising 50% of new boiler installations.

    Combi boilers and storage space

    Combi boilers provide central heating and hot water without the need for a hot water cylinder in an airing cupboard or a cold water tank in the loft. The combi boiler is not only an ideal space-saving solution, but it also limits the amount of wasted heat when compared to traditional models, as it does not have a hot water tank.

    Combi boilers and heating hot water

    Combi boilers take water from the mains and then heat it as required, but are on standby when there is no water demand. Therefore hot water is available 24/7 and also just as importantly, the water is delivered at mains pressure, so no pump is required to deliver the ‘power shower’ experience (provided your home has adequate mains water pressure).

    To produce the hot water that comes out of the taps, the cold mains water passes over a highly efficient heat exchanger. The heat exchanger transfers the vast majority of the heat from the burnt gas (90% or more) to the cold water, and then delivers it to the taps as required. Since combi boilers do away with the hot water tank, they are much more energy efficient, since there are no heat losses associated with stored hot water, it is simply created as needed.

    >>> Should I replace my conventional boiler with a combi? <<<

    Combi boilers and your central heating system

    On the central heating side, combi boilers pump the water round the heating system in a completely sealed system. The boiler incorporates an expansion tank internally, so there is no need for an external feed and expansion tank in the loft, which obviously saves a great deal of space.

    One of the issues with a combi boiler is that they struggle to produce both hot water and central heating at the same time, so priority is given to your domestic hot water whenever a hot water tap is opened in the home. For example, if you are running a bath, during this time no hot water will be circulated through your heating system, but as soon as the bath is full, the central heating circulation will resume.

    Combi boiler efficiency

    Since combi boilers don’t have to store any hot water, the heat losses via the hot water tank are zero, helping save you money on your gas bills.

    Most boilers installed today are condensing boilers, so if you choose a combi boiler, this will be a condensing model. These types of boilers use the heat contained within exhaust gases that would normally be released in to the atmosphere via the flue. They take advantage of heat exchangers to make the most of this latent heat, so less fuel is needed each time to heat the water, thereby further reducing your fuel costs.

    The main 2 issues with combi boilers

    The first issue is that since the hot water is produced at mains pressure, if the hot water is required in multiple outlets at the same time (e.g. a shower and the washing machine are running at the same time), there will be pressure drops at the different outlets. There are two solutions for this; firstly you can install a mains booster which recognises when pressure and flow are low and automatically boosts the performance of the incoming mains water. These cost in the region of £300 – £500. The second solution is to install an accumulator tank (approximately £500 – £1000 depending on the size), which is a steel vessel that stores mains water at the pressure it is supplied into the home. Air within the steel vessel (trapped in a rubber diaphragm) is compressed by the mains water. When a tap is opened, the water can rush out of the vessel to the tap faster than the mains can get into the property. The downside of the accumulator tank is that once all the water in the tank is gone, you have the same pressure issues that you would experience without it.

    The other issue is that if your combi boiler breaks, you will have no hot water generating facility other than the kettle. Most hot water tanks (within the system or regular boiler systems) come equipped with an electric immersion heater, so even if the boiler breaks you can still produce hot water for showers and baths (albeit in a rather expensive way).

    Final thoughts on combi boilers

    In homes where hot water demand is not huge, then a combi boiler is the most effective central heating/hot water system. They are very reliable and simple to install, they save space (since they do away with cold and hot water tanks) and produce the hot water on demand as it is required in the home. As a result, in most situations we would recommend installing this type of boiler when your current boiler reaches the end of its useful life.




    Installing a new boiler

    Are you thinking about getting a new boiler? If you would like us to find you a local installer to install a new boiler in your home, just fill in the form below and we will be in touch shortly!

      System Boilers


    What is a system boiler?

    System boilers are very similar to regular boilers; however they include some additional units in the boiler itself. There is an expansion vessel (which is required for vented hot water systems), as well as safety features like a pressure release valve which allows the boiler to release water if the pressure gets too high.

    System boilers always require a hot water tank

    They will always still require a hot water tank, since they create the hot water and then need to store it somewhere. However since a system boiler includes some of the components of a sealed system, such as the expansion vessel, then these will only ever be used in conjunction with an unvented hot water cylinder.

    System boilers do not require a cold water tank

    The great thing about a system boiler is that it means you can do away with cold water tanks altogether, which is obviously a nice space saver, although they still retain the hot water tank (unlike the combi boiler which does away with all external water tanks).

    The hot water storage tank is useful because it allows hot water to be vented at numerous sources (e.g. taps and showers) within the home without losing any water pressure – this is a problem sometimes experienced with combi boilers. However by producing and storing hot water before it is needed and not at the point of demand, there is more heat loss compared to a combi boiler. As a result the hot water storage tank itself will need an insulating coat to ensure that it keeps in as much heat as possible. In addition, you will need an easily accessible space to house the tank, which means cupboard space will have to be sacrificed.

    One of the major issues with a system boiler is that the hot water is limited by the size of your hot water tank. Therefore if you require a greater volume of water at any one moment than the capacity of your tank, you will need to wait until the boiler produces the hot water again (normally based on a timer system) – although this can be overridden by your heating controls if you know demand is going to be especially high.

    System boilers are more complicated since they include some of the components required in an unvented system. This means that they are more expensive than regular boilers, and they will also take up more space when they are installed.

    System boilers are compatible with solar thermal solutions

    System boilers are also compatible with solar thermal solutions. By creating hot water using the sun, you can also take advantage of the RHI scheme.

    System boiler installation

    Today any system boiler you may get installed within your home would most likely be a condensing system boiler. Much like a condensing combi boiler, a condensing system boiler reuses the heat contained within exhaust gases that would normally be released into the atmosphere via the flue, which makes it more efficient. They take advantage of heat exchangers to make the most of this latent heat, so less fuel is needed each time to heat the water, thereby further reducing your fuel costs.

    System boiler efficiencies

    It is possible to purchase A-rated condensing system boilers, which means that they convert more than 90% of the fuel into heat. These highly energy efficient system boilers will ensure you see large reductions in your heating bills – potentially over £300, depending on the boiler that you are replacing.




    Installing a new boiler

    Are you thinking about getting a new boiler? 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 install a new boiler in your home, just fill in the form below and we will be in touch shortly!

      CHP Boilers


    What are CHP boilers?

    Combined heat and power (CHP) boilers produce both heat and electricity in one single process. This process is sometimes referred to as cogeneration and the technology that supports it has been around since the 1970s, but has mainly been confined to industry and large dwellings such as hospitals and sports centres.

    As the price of fuel has increased over the last few years, it now makes economic sense to bring CHP technology into the domestic setting.

    A micro-CHP boiler is defined in the EU Act on Cogeneration as a domestic unit that is limited to 50kW of capacity.

    The different types of CHP boiler

    There are three types of micro-CHP boiler:

    The Stirling engine CHP boiler

    The Stirling engine CHP boiler is a type of external combustion engine, where the combustion engine is heated when the boiler is fired up to produce the hot water. This heats up the fully enclosed working gas within the Stirling engine, causing it to expand. The expansion of the working gas forces a piston to turn up and down between a copper coil, generating an electrical current, which can then be used in the home. The working gas usually used in a Stirling engine is helium, due to its strong heat transfer properties.

    The main limitation of this type of boiler is that it only produces electricity when you have the central heating on, so despite being a very efficient type of boiler, it does not produce an abundance of electricity. A key advantage is that the combustion process involved in a Stirling Engine CHP boiler is much quieter and more efficient than internal combustion engines.

    The internal engine CHP boiler

    This type of CHP boiler is commonly used in large dwellings such as hospitals. It involves using a fuel source to drive a turbine, which is connected to the electricity generator. The waste heat from this combustion process is captured to produce hot water for the space heating and warm water. This is the most common form of CHP boiler found to date. However the process is noisy and you have far less control over the hot water generated, so fuel cell and the Stirling engine CHP boilers are often preferred.

    Fuel cell CHP boiler

    Fuel cell CHP boilers use fuel cells which convert fuel and air directly into power and heat through a quiet, efficient, solid-state electro-chemical reaction. A video demonstration of how a fuel cell CHP boiler operates in the home can be found on the Ceres Power website.

    Fuel cells generate power significantly more efficiently than internal combustion and Stirling engine CHP boilers. This is because fuel cell CHPs convert chemical energy directly to an electrical current, maximising their efficiency.

    This type of CHP boiler is still in development so is not yet commercially available on a wide scale.

    How CHP boilers work in the house

    A home would typically use a boiler to meet its heating and hot water needs only, and then source its electricity from the grid. Central generation wastes a significant proportion of the energy it creates, through heat losses in the power station and in the transmission and distribution network.

    Micro-CHP boilers avoid these losses, and capture the heat for use within the home. This efficiency can save the consumer around 25% of total energy costs (around £600 off your bill if you have a typical 3-bed semi-detached house), and reduce each home’s CO2 emissions by up to 1.5 tonnes per annum. Micro-CHP boilers are designed to generate all of the heating and hot water and a significant percentage of the electricity needed by a typical UK home.

    The CHP boiler can use a variety of fuel options including the gas that is supplied by your current provider, but also hydrogen, LPG & biofuels. Even during the summer when the home’s central heating system is turned off, the heat produced by the micro-CHP boilers when generating electricity can be stored in a back-up hot water cylinder and then used for domestic hot water. Therefore the micro-CHP boilers are capable of operating all year round, maximising energy bill savings 365 days a year.

    Micro-CHP boilers are designed to one day replace your normal condensed boiler, using the same types of connections; they also have similar installation and maintenance requirements. A micro-CHP boiler only requires one connection to the electricity network in the house and it’s ready to go!

    Industry development

    Micro-CHP boilers are an example of a microgeneration product for the home. The UK Government has estimated that microgeneration products (such as micro-CHP boilers) have the potential to supply over 30% of the country’s total electricity needs and help meet its international environmental obligations, such as the 2020 EU carbon emission reduction targets. Owning a micro-CHP boiler is one step in the right direction. Full costs in the UK of a micro-CHP boiler including installation are yet to be made fully transparent; however incremental cost estimated in the region of £2,500 to £3,500 versus a condensing boiler, therefore a full installation is then estimated at between £5,000 to £7,000.

    Research commissioned by the Government has shown that micro-CHP boilers have the potential to become the micro-generation ‘system of choice’, replacing the condensing boiler, which is the standard system in most UK homes today. Commercial experience has also shown that realising the benefits early pays off the most over the long-term.

    Currently only the Stirling engine-type micro-CHP boilers have been made available on the domestic market. For example the Baxi Ecogen product is one of the few available micro-CHP boilers that is commercially viable and available for the home. By the middle-end of this decade, the expectation is that fuel cell models such as the Baxi Gamma 1.0 will be fully available to the UK consumers.

    When fuel cell micro-CHP technology is commercially available, the consumer should see the price of Stirling engine models fall. In addition with the competition in the fuel cell space (Baxi, Ceres Power, etc), this should also make those models commercially competitive. Current evidence suggests that the take-up in UK homes has only been limited, with a lower number of Micro-CHP boilers currently installed in the UK than expected by the government – as opposed to Denmark and Germany where the technology has been more widely adopted.

    CHP Boiler Technology Summary

    The following list is a quick summary of the CHP boiler features:

    Remember micro-CHP boilers are efficient because they generate heat and electricity in one place. They will save you money and help the environment. Currently only the sterling engine type of CHP boilers are available to the residential market (internal engine CHP boilers are available for large properties), but in a few years’ time fuel cell micro-CHPs will also be available. Micro-CHP boilers are a strategic domestic technology for micro-generation that will help homes with their energy needs, but also help the UK (and other EU countries) meet external carbon emission targets.





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