How to size a home battery: a plain-English guide
A home battery can make solar more useful and take advantage of cheaper off-peak tariffs. Getting the size right matters more than buying the biggest one.
Start with your usage
Look at how much electricity you use in a typical day, and when you use it: evenings, overnight or daytime. Your bills or smart meter app will show this.
Then look at your solar (if you have it)
If your panels often export spare power in the afternoon, a battery can store it for the evening. If you export very little, a big battery won't fill.
Then your tariff
On a time-of-use tariff, a battery can charge at cheaper times and run the home at peak times. That can make a battery worthwhile even without solar.
The rule of thumb
The best size is the one you'll actually fill and use most days. An oversized battery sits half-empty, and an undersized one runs out early in the evening.
Other things to check
Whether your existing inverter can work with a battery
Where the battery will go (garage, utility, outside wall)
The SP Energy Networks connection process (G98 or G99)
VAT
Home batteries are 0% VAT until 31 March 2027, including batteries added to existing solar.
Next step
FAQs
Do I need solar to have a battery?
No. On a time-of-use tariff, a battery can charge from the grid at off-peak times.
Can I add a battery later?
Often, yes. It depends on your inverter and wiring.
What VAT is charged?
0% until 31 March 2027.
Pentland Renewables surveys the property, sends a written quote, and arranges the work.
Send the form with your postcode and what you want priced. We survey your home, then send the written quote. You decide after you have read it.