Home battery storage
London
Store cheap overnight electricity and run the house on it through the expensive hours, or keep the solar you generate instead of exporting most of it. Fitted with or without panels, with 0 percent VAT.
- 5kWh battery from 3,500 pounds installed
- 0 percent VAT on home battery installations
- Works with or without solar panels
- Sized from your actual half-hourly usage, not a guess
10kWh: 5,500 to 7,000 pounds. 15kWh: 7,500 to 9,500 pounds.
- Electro Heating LimitedCompany 12609754, registered in England and Wales
- NICEIC and Gas Safe registeredHeld by the parent company
- MCS certifiedFor heat pump and solar work
- 10+ years in LondonSame engineers, same company
A home battery costs 3,500 to 4,500 pounds for 5kWh and 5,500 to 7,000 pounds for 10kWh installed, with 0 percent VAT, and it is worth fitting even without solar panels if you are on a time-of-use tariff.
The saving without solar comes from charging overnight at the cheap rate and discharging through the day. Whether that pays depends on the price spread on your tariff and on how much electricity your house actually uses.
Battery sizes and what they cost
| Capacity | Installed cost | Covers | Suits |
|---|---|---|---|
| 5 kWh | £3,500 to £4,500 | An evening and overnight for a small household | Flat or 2 bed house, no heat pump |
| 10 kWh | £5,500 to £7,000 | Most of a day for a typical family | 3 to 4 bed house, the common answer |
| 15 kWh | £7,500 to £9,500 | A full day including a heat pump in winter | Heat pump or EV in the house |
| 20 kWh and above | From £9,500 | Multi-day or high load | Large house, or a business |
Includes battery, hybrid or AC coupled inverter, electrical installation, DNO notification, commissioning and 0 percent VAT. Backup power in an outage is a separate specification and adds cost, so say if you want it.
The two ways a battery makes money
1. Storing your own solar
Without a battery, a London house typically uses only 40 to 50 percent of what its panels generate, because the panels produce most at midday when nobody is home. The rest is exported for a few pence and bought back later at four or five times the price. A battery flips that: self-consumption rises to roughly 70 to 85 percent.
2. Time shifting on a cheap tariff, with no panels at all
This is the case nobody explains properly. On a time-of-use tariff with a cheap overnight rate, you charge the battery at night and run the house on it through the expensive daytime and evening rates. There is no generation involved. The saving is purely the difference between the two prices, multiplied by the kilowatt hours you shift.
For a house with an air conditioning system running through July afternoons, or a heat pump running through a February, that difference adds up quickly, because those are exactly the loads that fall in the expensive hours.
Sizing it from your real usage
Most battery quotes are sized from the number of bedrooms, which tells you almost nothing. The right method is to look at your half-hourly consumption data, which your supplier can provide if you have a smart meter, and size the battery to cover the expensive window rather than the whole day.
- Typical London household, no heat pump or EV: 5 to 8 kWh used between 4pm and 8am. A 5 to 10kWh battery covers it.
- With a heat pump: winter overnight use can double. 10 to 15kWh.
- With an EV: the car is usually better charged directly on the cheap rate than through the battery, because putting energy through the battery twice loses some of it both ways.
- With air conditioning: the load falls in the afternoon peak, which is the most expensive part of most tariffs and the best case for storage.
What we fit and why
We use lithium iron phosphate batteries rather than older lithium chemistries, because they are more thermally stable, tolerate daily cycling better and hold capacity longer, which matters a lot when the battery is cycling every night on a time-of-use tariff rather than only when the sun shines.
Everything we install is notified to the distribution network operator and commissioned properly, with the certificates issued to you. A battery installed without DNO notification is a problem you inherit when you sell the house.
Battery storage questions
How much does home battery storage cost?
A 5kWh battery installed is typically 3,500 to 4,500 pounds, a 10kWh battery 5,500 to 7,000 pounds, and 15kWh 7,500 to 9,500 pounds. Those figures include the inverter work, the electrical installation and 0 percent VAT.
Retrofitting a battery to an existing solar system usually costs a little more than fitting both together, because an existing string inverter often needs an AC coupled battery inverter alongside it.
Is a battery worth it without solar panels?
It can be, and this is the part most installers skip. On a time-of-use tariff you charge the battery overnight at the cheap rate and discharge it through the expensive daytime hours. The saving comes from the price difference rather than from generation.
Whether it pays depends on the spread between your night and day rates and on how much electricity you actually use. For a house with a heat pump, an EV or air conditioning, the numbers are usually good. For a low-usage flat, often they are not, and we will say so.
What size battery do I need?
Look at your overnight and evening usage rather than your total. A typical London household without a heat pump or EV uses 5 to 8 kWh between 4pm and 8am, which is what a 5 to 10kWh battery is sized to cover.
Add a heat pump and that rises sharply in winter. Add an EV charging at home and the answer changes completely, because the car is usually better charged directly on the cheap rate than through the battery.
Will a battery keep my house running in a power cut?
Only if it is specified for it. A standard grid-tied battery shuts down in a power cut for safety, so that engineers working on the network are not exposed to your system backfeeding it.
Backup requires a battery and inverter that support an islanded mode, plus a changeover arrangement and usually a dedicated backup circuit. It adds cost and it has to be designed in from the start, so tell us at survey stage if it matters to you.
How long does a home battery last?
Modern lithium iron phosphate batteries are typically warranted for 10 years or a stated number of cycles, with around 70 to 80 percent of original capacity remaining at the end of the warranty period. In practice they carry on working past that with reduced capacity.
Cycle life is what matters if you are charging and discharging daily on a time-of-use tariff, because that is 365 cycles a year rather than the 200 or so a solar-only system does.
We will tell you if a battery is not worth it
Send your annual usage and your tariff. If the numbers do not work for your house we will say so, because a battery that never pays back is a bad advert for us.