How Solar Batteries Work With Your Solar System
A solar panel system generates electricity whenever the sun shines. If you're not home during the day, most of that electricity gets exported to the grid — often at a much lower rate than what you pay to import it. A battery stores that surplus energy so you can use it in the evening when your panels aren't generating.
Most home batteries are lithium-ion and range from 5 kWh to 15 kWh in usable capacity. A 10 kWh battery is the most common residential size — enough to cover the average home's evening and overnight consumption after a reasonably sunny day.
The financial logic is simple: instead of exporting at (for example) 4–15p/kWh and then importing at 25–35p/kWh later, you use your own stored electricity. The saving per kWh is the difference between those two rates.
Battery Costs by Country in 2026
Battery prices have fallen but remain a significant upfront cost. Here are typical installed prices for a 10 kWh home battery in 2026:
| Country | Battery Cost (installed) | Common Models |
|---|---|---|
| United Kingdom | £4,500–£7,500 | GivEnergy, Tesla Powerwall, Solax |
| United States | $9,000–$14,000 | Tesla Powerwall 3, Enphase IQ, LG RESU |
| Australia | A$8,000–A$13,000 | Tesla Powerwall, Sungrow, Alpha ESS |
| Canada | CA$10,000–CA$16,000 | Tesla Powerwall, Generac PWRcell |
| Ireland | €5,000–€8,500 | GivEnergy, Sungrow, BYD |
| New Zealand | NZ$10,000–NZ$16,000 | Tesla Powerwall, Alpha ESS |
Prices vary by battery brand, capacity, and installer. Some installations benefit from government incentives that can reduce costs by 10–30%.
How Much Can You Save With a Battery?
Battery savings come from two sources:
- Avoided import cost: Using stored solar instead of grid electricity during the evening. If you store and use 5 kWh per day at 28p/kWh rather than exporting it at 6p/kWh, you save 22p × 5 kWh = £1.10 per day, or roughly £400 per year in the UK.
- Time-of-use tariff arbitrage: Some batteries can charge from cheap overnight grid electricity and discharge during expensive peak hours, adding further savings independent of your solar generation.
In practice, annual battery savings range from:
- UK: £300–£600/year
- US: $400–$900/year (varies enormously by state tariff)
- Australia: A$700–A$1,400/year (excellent export/import spread)
- Ireland: €200–€450/year (modest gap between export and import rates)
These are the additional savings over solar panels alone — not the total system savings.
Battery Payback Period by Country
Dividing the battery cost by annual savings gives a rough payback period. Here's what that looks like in 2026:
| Country | Battery Cost | Annual Saving | Payback Period |
|---|---|---|---|
| United Kingdom | £5,500 | £420/yr | ~13 years |
| United States | $11,000 | $620/yr | ~18 years |
| Australia | A$10,000 | A$1,100/yr | ~9 years |
| Canada | CA$12,000 | CA$550/yr | ~22 years |
| Ireland | €6,500 | €320/yr | ~20 years |
| New Zealand | NZ$12,000 | NZ$850/yr | ~14 years |
These are mid-range estimates. A battery's warranted lifespan is typically 10–15 years. This means Australia and possibly the UK are the strongest financial cases for batteries in 2026. In markets like the US and Canada, payback often exceeds the warranty period — though batteries frequently outlast their warranty by several years.
When a Battery Makes Sense
A solar battery is most likely to be financially worthwhile if:
- You have a high export-import rate gap. If you export at 5p but import at 30p, storing your own energy is highly valuable. If your export rate is 18p and import is 25p, the benefit is much smaller.
- You use a lot of electricity in the evening. If you're at home during the day, you already self-consume most solar directly — a battery adds less value. If you're out until 6pm and then use heavy appliances, a battery captures what would otherwise be wasted.
- You have a large solar system. A 3 kW system rarely generates large surpluses. A 6–10 kW system regularly exports significant amounts, especially in summer.
- You're on a time-of-use tariff. Tariffs like Octopus Agile in the UK allow batteries to charge at near-zero overnight prices, adding savings beyond solar.
- Energy security matters to you. In areas with grid outages, battery backup has a non-financial value that can justify the cost.
When a Battery Might Not Be Worth It
Skip the battery if:
- Your export rate is already close to your import rate (e.g. Ireland's smart export tariff at €0.185 vs. €0.30 import — the financial case is weak).
- You have a small solar system (under 4 kW) that rarely generates large surpluses.
- Your household uses most solar during the day already (self-employed workers at home, heat pumps, EV charging during daylight hours).
- The payback period exceeds the warranty period by a large margin in your location.
A battery is rarely a bad product — it's more a question of whether the financial math works in your specific situation. Our solar battery calculator lets you enter your actual rates and usage to get personalised numbers.