Choosing
Solar only, battery only, or both?
The routes side by side
| Route | Typical price | Saves a year | Payback |
|---|---|---|---|
| Solar only, 4 kWp | £5,500 to £7,500 | £490 to £730 | 9 to 12 years |
| Solar 4.5 kWp and 5 kWh battery | £8,500 to £12,500 | £640 to £960 | 11 to 16 years |
| 5 kWh battery on existing solar | £2,750 to £4,750 | £90 to £130 | 25 to 43 years |
| 5 kWh battery, cheap overnight rate, no solar | £2,750 to £4,750 | £180 to £270 | 12 to 21 years |
Estimates as of October 2026. They assume 0% VAT, 3,000 kWh a year, and 10p for the cheap overnight rate. Not quotes.
Solar only fits if
- Someone is usually home in the day.
- You want the shortest payback on the table.
- You are unsure about a battery. You can add one later, though a later job may carry 5% VAT after 31 March 2027.
Solar only is the plain option and, on our numbers, the cheapest way to cut a bill. Panels do their work whether or not anyone is in, and whatever you do not use is sold to your supplier. The battery in the middle row of the table is what you buy if that sold power bothers you. See solar only.
One more point. If you pick solar only, tell the installer you may add a battery in a few years. They can then choose an inverter that will accept one, and that costs far less than swapping it later.
Both fits if
- The house is empty all day and busy from teatime.
- You have an electric car or heat pump, or plan one.
- You want some cover when the grid goes down, and will pay for it.
The table shows the cost: the payback runs 11 to 16 years against 9 to 12 for solar alone. The battery is a convenience you pay for, and the number is not massaged. Details on solar and battery.
Plenty of people buy both for reasons that are not on the table, and that is fine, as long as you know which reasons they are. If the honest answer is that you like using your own power in the evening, the sums will not argue with you, but they will not agree either.
A note on budget
Money is often the deciding factor, not the sums. If you have about £5,500 to £7,500 to spend, solar only is within reach. If you have £8,500 to £12,500, the pairing is. A battery on its own sits around £2,750 to £4,750, and that is the one with the longest payback. Spend what makes the sums work, not what the quote allows.
Battery only fits if
- You already have solar and export a lot.
- You have a smart meter and can use a cheap-rate tariff that suits a battery.
- The roof is unusable, and you accept a long payback for flexibility.
Read the battery only page and the tariff guide first.
The fourth route
If you live in a flat, rent, or just want a small start with no roof work, plug-in solar is a separate route with its own rules. Only approved kits are allowed, each is limited to 800W, you can have one per home, you must register it before use on the UK Plug-in Solar Registration website, and renters and flat owners need permission from the landlord or freeholder. Read our plug-in page first.
Questions people ask
Which pays back fastest?
Solar only, on our numbers. Batteries pay back slowly unless a cheap overnight rate keeps them busy.
Can I start with solar and add a battery later?
Yes. Ask for an inverter that suits a battery so you do not pay twice.
Is a bigger system always better?
No. Size it to your roof and your use. See the sizing guide.
Where do I start?
Run your bill through the estimator, then ask for a survey of the roof.
Want numbers for your own house? Try the estimator or ask for a free quote.
Sources
- Energy Saving Trust: solar panels
- Energy Saving Trust: battery storage
- GOV.UK: VAT Notice 708/6, energy-saving materials
- Energy Saving Trust: plug-in solar panels
More guides
- What solar and a battery cost for a Faversham house
- Is a home battery worth it?
- What size solar and battery do I need?
- 0% VAT on solar and batteries, and what it means
- Planning permission and network approval in Faversham
- Cheap overnight tariffs and home batteries
- Pairing an EV charger with solar and battery
- Smart Export Guarantee: real rates, October 2026
- Solar by house type in Faversham