Is a solar battery worth it?
A battery makes no electricity at all. What it does is move electricity from when you have it to when you need it — and whether that is worth buying depends almost entirely on two things about your household.
Solar panels generate most in the middle of the day. Most households use most in the morning and the evening. That mismatch is the entire problem a battery solves, and it is worth understanding before anybody quotes you.
What actually happens without one
Your house takes what it needs from the roof as it is generated. Everything else is exported to the grid, and your supplier pays you for it under the Smart Export Guarantee. Then in the evening, when the panels have stopped, you buy electricity back.
The catch is the gap between the two prices. You are paid one rate for what you export and charged a different, higher one for what you import. A battery closes that gap by keeping your own generation for your own evening.
The two things that decide it
1. Your tariff
This matters more than the panels do. On a single flat rate all day, a battery only helps with solar — it stores what you generated. On a tariff with cheap overnight hours, it does something else entirely: it fills up overnight at the low rate and runs the house through the expensive part of the day.
The part people miss. On an off-peak tariff a battery is worth having even with no solar at all. It is arbitraging the price difference between night and day rather than storing sunshine.
2. When you are actually in
A household that is out all day and home all evening gets the most from a battery, because almost none of the generation would otherwise be used. A household with someone home during the day is already using the roof output as it happens, so there is less to store.
What it will not do
- It will not make you more electricity. The panels do that. A battery only changes the timing.
- It will not usually keep the lights on in a power cut unless it has been specified for that, which is a different installation with different equipment.
- It will not pay for itself on every tariff. On a flat rate, with a small array and someone home all day, the case is weak and we will tell you so.
Sizing it
Bigger is not automatically better. A battery larger than your evening use spends its life part-full, which is capacity you paid for and do not use. The sizing comes from your actual consumption, which your smart meter data shows.
That is why we ask for the data rather than guessing from the size of the house. Two identical houses can differ by a factor of three.
Retrofitting to an existing array
Yes, in most cases. Whether the existing inverter can take it depends on what was fitted — some can, some need an additional battery inverter alongside. It does not usually mean replacing the panels.
If your system was installed before about 2016 it may be on the old Feed-in Tariff. Adding storage does not affect those payments, but the paperwork is worth getting right, and we handle that.
VAT
Battery storage is zero-rated for VAT until 31 March 2027, fitted alongside solar or on its own.
Sources. Tariff behaviour varies by supplier and by tariff. VAT position as published by the UK government at the date shown above. Sizing comes from your own smart meter data at the survey, not from a rule of thumb.