Aside from adding a battery, the best approach is to try to match your electricity usage with your electricity generation. For example, run appliances when the sun is shining, but spread them out to avoid demand spikes.
You can also looking into storing energy as heat, or switch more of your systems, equipment and appliance to electric (see ‘Complementary technologies below’).
You may well have to replace the inverter (the box that converts direct current from the panels mains alternating current) after 10 – 15 years at a cost of perhaps £800 at 2022 prices. The panels themselves should still produce at least 80% of initial power after 25 years.
For batteries, many manufacturers provide a warranty 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.
In the interests of ensuring that we get a good spread of CCG applications from new groups and areas, we will restrict the total number of smaller grants over the lifetime of the fund. We can award a maximum of three small grants per group – up to a total amount of £2,000. Or a maximum of two medium grants per group – up to a total amount of £3,000. If you wish to apply for a combination of small and medium grants, the total amount should not exceed £3,000. This restriction does not prohibit groups who have previously been successful in achieving small or medium grant funding from applying for large grants (up to £10,000) when those funding rounds are announced. Please get in touch with [email protected] if you have any queries regarding this policy.
The other consideration is whether you have any birds nesting in your walls or eaves. It is illegal to disturb them, so you should ensure that there aren’t any before installing panels or erecting scaffolding. Whilst house martins and house sparrows are usually obvious, swifts may not be. If they are present, the work should not be carried out – or scaffolding erected – between mid-April and mid-August.
If bats are discovered before or during a planned installation, extra consideration must be taken. A licence may need to be obtained from you Statutory Nature Conservation Organisation. Further details can be found at: Solar panels – Things to consider when planning works – Bat Conservation Trust (bats.org.uk)
They should be covered by your buildings insurance, but we recommend that you contact your insurer to confirm this.
Experience suggests that with a 10kWh battery you may be able to use about 70% of the 3,400kWh you produce even if you use only 30% directly, i.e. an extra 1,360kWh. Then, your battery will save you 1,360kWh at 34p, i.e. £460 pa. Assuming the battery costs £6,000 the payback time is about 13 years, longer than the currently expected lifetime of the battery. Taking the efficiency of the battery (about 90%) into account the saving reduces to about £420 and the payback time increases to about 14 years.
At 5p per exported unit and assuming you use 30% of what your panels produce, your excess of 2,380kWh pa will provide £118 income. Your total savings will now be about £460 pa and your payback time reduces to 13 years. If you use more than 30% in your home the time is less.
Let’s assume that you pay 34p per kWh for grid electricity and use 30% of what your panels produce, i.e. about 1,020kWh. Then you will save about £350 pa and your £6,000 will take 17 years to pay off. If you use 45% the payback period comes down to 12 years and for 60% it’s 9 years.
Quotes from some installers will make assumptions about inflation rates and will get smaller payback periods. You have to make your own judgement on how much weight to give to this but there seems to be general agreement that electricity prices will continue to rise in the coming years. For every increase in the cost of electricity that happens, the payback period for your panels comes down.
If you have an electric car, or are planning to get one, you may want to consider installing an electric vehicle charge point. 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 is at home and plugged in. If plugged in during the day, it could store electricity generated by your solar panels. If plugged in at night, it could store lower carbon and potentially lower cost night-time grid .
There are technological developments around water heaters that have smart controls and can be directly connected to your solar PV electricity supply, as well as your other energy sources. Have a look at Mixergy and iBoost as examples, but note that we have no experience of actually using these products. Storing excess electricity as hot water is another way of maximising the electricity output from your panels. An example of a homeowner who has adopted lots of complementary technologies is presented in this video presentation.
There are also heat batteries. As explained by the Energy Saving Trust, these store either spare heat or electricity, often generated by renewable energy systems. Heat can be stored in a material when it changes phase from a solid to a liquid. These materials are called phase change materials (PCM). Spare heat or electricity is used to charge the PCM inside the heat battery. When the heat is needed, the phase change material changes back into a solid with a release of heat, which is used to provide hot water.
Whilst a battery does not save carbon in itself, it does mean that the carbon and cost savings from the solar PV are maximised. Renewable energy generation is not constant – it fluctuates depending on the weather. Similarly, there are peaks and troughs in demand for electricity. If we can store excess green electricity and use it later, the UK electricity grid does not need to rely so heavily on electricity generated by fossil fuels to meet peak demand. As well as storing excess electricity that your solar panels generate during the day, you can store electricity at night from the grid, when demand is lower, and the electricity mix is greener.
Adding a battery to a solar PV system has become very common.
Please note, if you install a battery as part of your solar PV system, the whole thing is exempt from VAT. However, as batteries are not classed as energy saving measures in their own right, they are subject to VAT if installed separately i.e. at a later date. Therefore, you may lose out financially if you postpone the decision to get a battery, plus the job may be less attractive to installers.