Tesla Powerwall Working in Combination with Solar PV

With a 90% efficiency rate, the Tesla Powerwall is a leading technology being used in homes to save energy by working in sync with solar PV systems. Solar PV is a renewable energy source for many homes across the world, using sunlight to generate electricity. The Tesla Powerwall is a chance for homeowners to improve their solar PV systems by storing excess electricity and allowing it to be used in the home instead of being exported back to the grid.

What is the Tesla Powerwall?

The Tesla Powerwall is a battery storage system that was launched in 2015 by entrepreneur Elon Musk, with hopes of saving energy and money for the homeowner. It consists of a rechargeable lithium-ion battery, and is designed to store excess energy generated in off peak times. For example, on a sunny day solar PV can generate more electricity than you need, and without storage this would be exported back to the grid.

For those with older solar PV systems the ability to store excess electricity is particularly useful because of the Feed-in Tariff. The feed-in tariff pays those with solar PV systems for producing electricity, but you also get paid for exporting electricity back to the grid. Typically older solar PV systems never had an export meter installed, so the energy companies didn’t know how much electricity was being exported – instead they paid you 50% of what was generated – regardless of whether you exported 0% or 100%.

Therefore, in this instance it makes sense to store all the electricity and export as little as possible back to the grid. The owner of the Solar PV system will be paid as if they are exporting 50% of what is produced regardless, but they benefit from being able to use all the electricity they produce!

If you find yourself in the position where the the sun isn’t shining (so your solar PV system is unable to generate any electricity), and there is also no stored energy in the Tesla Powerwall, then you don’t need to panic – the Tesla Powerwall is connected directly to the grid, so you can still use electricity as normal, although you do have to pay for it!

Why should I install a Tesla Powerwall in combination with Solar PV?

  1. It provides an interruptible power supply. The Tesla Powerwall is fitted with a back-up gateway which can predict power cuts, by communicating with the grid. The Tesla Powerwall can then prepare and ensure electricity supply in your home during a power cut.
  2. A solar Powerwall system allows you to use all the electricity you produce from your solar PV system even if there is little demand for the electricity as it is being produced (i.e. you can produce it during the day and then use the electricity when you come back from work in the evenings).
  3. By using more of the electricity you have created for free – you are saving on your energy bills.
  4. The Tesla Powerwall can be installed indoors or outdoors which makes it an easily accessible appliance for maintenance.
  5. It works using AC power not DC, therefore is easy to install alongside existing solar PV systems.
  6. If you are on an economy electricity tariff, such as Economy 7, where electricity rates are cheaper at off-peak times, it could save you even more money. By charging your Tesla Powerwall overnight (an off-peak time) using grid electricity, it will save you having to charge it in the daytime at a higher rate.
  7. The Tesla Powerwall comes with a mobile app which notifies you of potential risks to your power supply (such as bad weather) and it also keeps track of your power flow. The power flow reports on demand, solar PV energy generation, and how much grid energy you are using.

How will it work in my home?

How much electricity will the Tesla Powerwall in combination with solar PV supply?

An average house in the UK uses 10KWh of electricity every 24 hours. The Tesla Powerwall has a maximum storage capacity of 13.5KWh, meaning it could power a house for a full day without having to recharge. However, this depends on the demand for electricity in the house as well. The Tesla Powerwall has a maximum power output of 5kW at one time, therefore most household electric appliances are covered by the stored electricity, however some higher wattage appliances are not. An electric shower (10kW) or an electric vehicle charger (7kW) would only be partially covered. This would mean the shortfall in electricity would need to be pulled from the grid (or solar system)

How many solar panels are needed to recharge the Tesla Powerwall?

Well, a 4KW solar PV system (16 panels) can produce 20KWh on an average sunny day which would fully charge the battery and supply enough electricity to run the home. However, in winter when there is less sunshine and sunlight, a 4KW solar PV system might only produce quarter of what it does in the summer. Therefore, there will be less electricity generated from the solar PV system, and less to recharge the battery. Due to this lack of stored electricity the demand for the grid will increase.

Can you install the Tesla Powerwall and Solar PV system in commercial buildings?

Yes you can! More batteries will need to be installed to ensure enough electricity is stored for the amount of people it is providing. Larger buildings will also need more or bigger solar panels, as they will need to generate more energy. The size of a solar panel depicts how much energy is generated per square metre. Compared to domestic properties, larger buildings home to businesses use electricity on a much larger scale, due to electrical appliances such as computers, machinery and kitchen equipment being used every day non-stop. So, by creating and storing their own energy this will save the business money in the long term.

How much does the Tesla Powerwall and Solar PV system cost?

The Tesla Powerwall 2 is priced at £5500 and up for the maximum storage capacity of 13.5KWh. If you have an existing solar PV system this is a reasonable price to start saving energy and money in your home. However, if you happen to be new to this with nothing in place already, you are looking at a much higher price. A 4KW solar PV system costs around £5000, which doubles the complete installation of both solar PV and the Tesla Powerwall 2. Most installers of the system are quoting between £8600-£10,500 depending on the complexity of the system.

The Tesla Powerwall does come with a 10-year warranty, providing some security to the customer. It is predicted to last many years longer, however keeping in mind that the capacity will reduce gradually over time. If the capacity falls below 80% of the original amount during the 10-year warranty, you will be guaranteed a replacement.

How much will the Tesla Powerwall and Solar PV system save me?

A solar PV system on its own saves £700-£800 a year in a domestic property, It is proven that the system will pay for itself in 9.5 years if electricity usage is average. Additionally, if the system is in place for 20 years, you will see a £5000-£6500 profit!

With the Tesla Powerwall 2 added to the solar PV system it will increase these savings dramatically. By allowing you to store the excess electricity generated from your solar PV system it is reducing the dependency on the grid even more. It is also increasing the possibility of your home running entirely on your own generated, renewable energy.