Solar and battery
Solar and battery calculator
The question is rarely 'does solar work' — it is whether the battery on the same quotation earns its extra cost. This compares the options consistently, on one model.
The calculator is free, needs no account, and keeps your figures in your own browser.
Compare all three optionsPrefer to look at one part at a time? The solar and battery calculators work through each side separately.
Three options, one set of numbers
No solar, solar alone, and the same solar with a battery are run through the same hourly model with identical household demand, prices and standing charges. That makes the incremental battery saving meaningful rather than the sum of two separate tools.
The number to look at
Not the combined saving, but the difference between solar alone and solar with the battery — set against the extra cost of the battery on your quotation. If that gap is small, a smaller battery or no battery may be the better decision.
Total use, not just grid import
If you already have solar, the electricity you buy from the grid is less than the electricity your home uses. The comparison asks you to confirm total annual consumption so the options are not quietly compared on the wrong figure.
Common questions
- Is it worth adding a battery to a solar quote?
- Judge it on the extra cost against the extra saving, not on the combined system. The battery only earns money on units it actually stores and releases, so a battery larger than your daily surplus and evening demand adds cost faster than saving.
- How is the solar and battery saving modelled?
- An hour-by-hour model runs the same household demand, the same solar shape and the same prices through each option: no solar, solar alone, and the same solar with a battery. Comparing options on one model avoids double counting.
- What size battery suits a home with solar?
- Enough to soak up a typical day's surplus and cover the evening, which for many homes is a modest size rather than the largest on offer. The calculator compares several sizes so you can see where the extra saving starts to flatten off.
- Does round-trip efficiency and backup reserve matter?
- Yes. Some energy is lost charging and discharging, and any reserve kept for power cuts is not available for everyday savings. Both are adjustable so you can see how much they change the result.
- Can a battery pay without solar?
- Sometimes, by charging on a cheap overnight rate and discharging at the day rate. The saving then depends on the gap between those two prices and how much you can shift, which the battery calculator models directly.