Calculate your savings
Assumes one full charge/discharge cycle per day at 90% round-trip efficiency. Actual savings depend on usage patterns.
How the savings calculation works
The savings from a home battery come from the tariff spread – the difference between what you pay during cheap off-peak hours and what you'd pay during expensive peak hours. Here's the formula:
Usable capacity = battery capacity × 0.9 (efficiency)
Example (10kWh on Octopus Go):
For a 10kWh battery: (9kWh × 33.5p) − (10kWh × 9.5p) = 206.5p/day, or approximately £754/year
Savings comparison by tariff
| Tariff | Off-peak | Peak | Spread | Annual (10kWh) |
|---|---|---|---|---|
| Octopus Go | 9.5p | ~33p | ~23p | ~£755 |
| Intelligent Octopus Go (requires EV) | 8p | ~34p | ~26p | ~£854 |
| Economy 7 | ~14p | ~30p | ~16p | ~£525 |
What about payback?
Your payback period is simply the cost of your battery system divided by your annual savings. For a 10kWh system:
| Tariff | Annual saving | Payback (£5,500 system) | Net saving over 12 years |
|---|---|---|---|
| Octopus Go | £755 | ~7.3 years | ~£3,560 |
| Intelligent Octopus Go (requires EV) | £854 | ~6.4 years | ~£4,748 |
| Economy 7 | £525 | ~10.5 years | ~£800 |
Factors that affect your savings
Your tariff spread is the biggest factor. A bigger gap between off-peak and peak rates means more savings. On a flat-rate tariff with no off-peak period, a standalone battery saves nothing.
Battery size determines how much energy you can shift per day. A 10kWh battery shifts roughly twice as much as a 5kWh – and saves roughly twice as much.
Your actual usage matters too. If you use less electricity during peak hours than your battery can supply, the excess capacity goes unused. A battery matched to your peak-hour consumption delivers the best returns.
Round-trip efficiency – the energy lost during charging and discharging – is typically 88-92% for modern LiFePO4 batteries. Our calculator uses 90% as a conservative estimate.
Like what you see?
Ready to start saving? Reserve your Habo Energy battery with a refundable deposit.
Reserve for £49