FAQs

Currently it is worth it in relation to supporting the grid to smooth out national peak renewable energy generation to better meet peak demand, and, with some careful attention, is likely to pay itself back over time.   Before investing, it is worth considering whether you are likely to be charging an electric vehicle in the near future. If so, technology is evolving to allow “bi-directional charging” which means that you can store electricity in your vehicle battery in the same way as a stand-alone battery and then use it in your house. That does however depend on when your vehicle [...]

It’s difficult to be certain, but probably yes. Part of the calculation depends on the difference between peak and off-peak rates, but with electricity prices expected to rise it could well improve. 

This is not straightforward and depends significantly on how much you pay to charge your battery overnight in winter: your present supplier may well not have an appropriate low night-time rate.  If you have a battery of about 10kWh and store enough electricity from your panels to keep your house running overnight (and all day during dull winter days) you may not have to buy much electricity at daytime rates. In this case the payback time could be around ten years, similar to the reasonable expectation for battery life – see below for the calculation 

The addition of a battery to your system can greatly increase the amount of solar power you can use and hence reduce the amount you need to buy from the grid. Some electricity suppliers also allow you to charge your battery overnight at an off-peak rate and this can produce reductions in your electricity bill in winter.   However, you should consider how big a battery to buy and financial return. Obtain a separate quote from installers for a battery rather than let it be rolled into a quote for panels plus battery. If you do get a quote, it could [...]

Many manufacturers provide a warranty for their battery of perhaps 10 years or some number of cycles (filling and emptying the battery), whichever is the smaller, with some level of degradation, for example 20%. However, it’s too early to know what the lifetime of batteries will be in practice.  

Installers often encourage you to buy a battery to store electricity, but you should know that the environmental and financial aspects are rather different to those for solar panels. Treat the purchase of a storage battery as a separate decision with different considerations.   Whilst a battery does not save additional carbon in itself, it does mean that the carbon savings from the solar PV are maximised. At times of national peak electricity demand, the UK grid relies more heavily on electricity generated by fossil fuels. The more renewable electricity that can be stored during times of peak renewable energy generation, [...]