For a low-use home, yes. For a typical one, for most of the year. Ofgem's typical values from July 2026 put a medium home at 2,500 kWh a year, which in this site's model is about 4.1 kWh a day outside solar hours on average and 5.0 kWh on a December day. Batteries sold as 5 kWh deliver about 4.1 to 5.3 kWh after charging losses, so most cover that home's average evening and only the largest covers a December one. On a flat tariff with solar that rarely matters; on a time-of-use tariff a 10 kWh battery saves far more.
Guide · Published by SEO Dons Ltd · Updated 6 October 2026
How much a house uses when the sun is down
A battery is only as useful as the energy it can move each day, so the starting point is how much electricity your home uses when solar panels are not generating. Ofgem revised its typical household figures on 1 July 2026, lowering each of them. This site’s model assumes 60% of a home’s electricity is used outside solar hours, and scales each month by the season, so December use runs about a fifth above the yearly average:
| Household (Ofgem, from July 2026) | Use a year | Average a day | Outside solar hours, average day | Outside solar hours, December day |
|---|---|---|---|---|
| Low | 1,600 kWh | 4.4 kWh | 2.6 kWh | 3.2 kWh |
| Medium | 2,500 kWh | 6.8 kWh | 4.1 kWh | 5.0 kWh |
| High | 3,800 kWh | 10.4 kWh | 6.2 kWh | 7.6 kWh |
| Heat pump or electric car | 6,000 kWh | 16.4 kWh | 9.9 kWh | 12.0 kWh |
The high-use and heat pump figures are where 5 kWh clearly runs out. The medium home is the borderline case, and it is the one most people are asking about.
What “5 kWh” actually delivers
Two things shrink the number on the label. Batteries keep a reserve, so the usable capacity is lower than the nominal one, and charging and discharging lose energy along the way; this site’s model assumes 10% over a full cycle. Among products commonly sold as 5 kWh:
| Usable capacity | Examples | Delivered to the house after losses |
|---|---|---|
| 4.6 kWh | Sunsynk Elite, myenergi libbi 5 kWh module | about 4.1 kWh |
| 5.0 kWh | Enphase IQ Battery 5P | about 4.5 kWh |
| 5.84 kWh | Sigenergy SigenStor BAT 6.0 | about 5.3 kWh |
Set against the first table, a 4.6 kWh product just covers the medium home’s average evening and falls about 0.8 kWh short on a December one. The Sigenergy unit covers both. For the low-use home, any of them is enough all year; for the high-use home, none is.
When 5 kWh is enough, tariff by tariff
Coverage is not the same as savings. What the battery saves depends on the tariff, and on some tariffs a battery bigger than the evening load still earns. This site’s model, for a London home with the same annual use, compares 5 kWh and 10 kWh:
| Household | Flat tariff, 4 kWp solar: 5 / 10 kWh | Octopus Flux, 4 kWp solar: 5 / 10 kWh | Agile Octopus, no solar: 5 / 10 kWh |
|---|---|---|---|
| Low, 1,600 kWh | £120 / £120 | £186 / £438 | £175 / £182 |
| Medium, 2,500 kWh | £159 / £159 | £176 / £423 | £196 / £285 |
| High, 3,800 kWh | £159 / £190 | £177 / £399 | £210 / £379 |
Modelled annual savings at Octopus’s London rates for 26 September 2026.
So 5 kWh is enough in two situations. On a flat tariff with solar, the low and medium homes save exactly the same with 5 kWh as with 10, because the battery’s only job is to hold surplus solar for the evening. And a low-use home without solar on Agile gains just an extra £7 a year from doubling the size.
It is not enough on Octopus Flux, where a bigger battery is paid for exporting stored energy at the evening peak whatever the home’s use, or for medium and high users on an overnight tariff. Our analysis of whether a bigger battery saves more shows what the second 5 kWh costs and how fast it pays back.
The winter gap, and what it costs
When a 5 kWh battery runs short on a December evening, the house simply draws the rest from the grid at whatever rate applies then. For the medium home that is about 0.8 kWh a day with a 4.6 kWh product. On a flat tariff it costs nothing extra compared with having no battery for that part of the evening. On a tariff with an expensive 4pm to 7pm peak, it is bought at the peak rate, which is the main reason time-of-use homes do better with more capacity.
How to check your own home
- Find your yearly use on your bill or your supplier’s app.
- Divide by 365 and take 60% of it: that is roughly what you use outside solar hours. Add a fifth for December.
- Compare it with what the battery delivers after losses, not with the number on the label.
- Then look at your tariff. On a flat tariff, match the battery to your evening; on a time-of-use tariff, run the calculator at both sizes.
If your evening figure is under about 4 kWh, a 5kWh battery covers it with room to spare, and modular products let you add capacity later if an electric car or heat pump arrives.
If 5 kWh turns out to be too small, the next price to check is in the solar battery cost guide, which shows what the average installation of each size cost in 2025/26. For a pick by situation across all sizes, see the best solar battery guide.
Questions people ask
How many kWh does a house use in an evening?
Ofgem's typical values from July 2026 are 1,600, 2,500 and 3,800 kWh a year for low, medium and high use on a single-rate meter. This site's model assumes about 60% of use falls outside solar hours, which works out at about 2.6, 4.1 and 6.2 kWh a day on average, and roughly a fifth more in December.
Will a 5 kWh battery last all night?
For a low-use home, usually; for a medium one, on most nights outside winter. A battery sold as 5 kWh holds 4.6 to 5.84 kWh you can use, depending on the product, and loses about 10% of what goes in to charging and discharging. That leaves about 4.1 to 5.3 kWh for the house, against about 4.1 kWh used outside solar hours on an average day by a 2,500 kWh home and 5.0 kWh in December.
Is 5kWh enough with a heat pump or electric car?
No. A home using 6,000 kWh a year, typical of a heat pump or an electric car charged at home, uses about 9.9 kWh a day outside solar hours on average and about 12 kWh in December in this site's model. On Octopus Go that home saves £425 a year with 10 kWh but only £73 with 5 kWh.
Can a 5 kWh battery run an electric shower or an oven?
Capacity is not the limit there; power is. A battery delivers only as many kilowatts as its inverter allows, and 5 kWh products are commonly paired with inverters of about 3.2 to 5 kW. A 9 kW electric shower draws more than that, so the rest comes from the grid. Ask for the continuous output in kW as well as the capacity in kWh.