The maths
(Octopus Go)
(Octopus Go, by region)
(after efficiency)
(5 kWh, per year)
Best-case range for a 5 kWh battery, one full cycle a day, on Octopus Go 12M Fixed (checked 10 October 2026), so real savings will be lower. Daytime rate varies by region. See how we worked it out. Check your region.
Savings by battery size
| Battery Size | Daily Savings | Annual Savings | Payback (approx.) |
|---|---|---|---|
| 5 kWh (Habo EcoFlow STREAM) | up to £1.15 to £1.34 | up to £420 to £490 (best case) | 5.1 to 6.0 years on £2,499 (best case) |
| 10 kWh | ~£2.07 | ~£755 | depends on installed cost, typically 6–8 years |
| 11.5 kWh (typical UK install) | ~£2.38 | ~£870 | depends on installed cost, not the Habo product |
| 15 kWh | ~£3.10 | ~£1,130 | depends on installed cost |
These figures assume daily cycling and account for ~90% round-trip efficiency. Your actual savings depend on your usage patterns and tariff rates. Habo sells the 5 kWh row. The larger sizes are honest other-size maths, not Habo SKUs. For help choosing between tariffs, see our guide to the best tariffs for battery storage.
How the calculation works
Take the Habo Energy 5 kWh EcoFlow STREAM on Octopus Go 12M Fixed (checked 10 October 2026). The night rate is 9.5p/kWh and the day rate runs from 33.555p/kWh (Yorkshire) to 37.4209p/kWh (Merseyside and North Wales). EcoFlow does not publish a round-trip efficiency, so we assume 90%: to deliver 5 kWh you buy 5 / 0.9 = 5.556 kWh overnight.
Cost to charge overnight: 5.556 kWh x 9.5p = 52.78p
Value of 5 kWh at the day rate: 5 kWh x 33.555p = 167.78p, up to 5 kWh x 37.4209p = 187.10p
Daily saving: 115.00p to 134.33p
Annual saving: x 365 = £419.74 to £490.29
That is a best case: one full cycle every day, all used at the day rate, so real savings will be lower. It is up to about £35 to £41 a month, not £70 to £80. See how we worked it out. Check your region's exact rate.
Savings by tariff (5 kWh)
| Tariff | Off-peak rate | Peak rate | Annual saving (5 kWh) |
|---|---|---|---|
| Octopus Go | 9.5p | 33.6p to 37.4p | up to £420 to £490 (best case) |
| Intelligent Octopus Go (requires EV) | Check your Octopus rates | Depends on your rates: use the calculator | |
| Economy 7 | Rates vary by supplier and region | Depends on your rates: use the calculator | |
What about after payback?
Once your battery has paid for itself, in about 5.1 to 6.0 years on £2,499 in the best case, every year after that is the annual saving. With a battery lifespan of 10 to 15 years, that is potentially several years of up to £420 to £490. Do not stack old 11.5 kWh lifetime totals onto the new 5 kWh price. For a detailed breakdown of upfront costs, see our home battery storage cost guide.
More savings with solar
If you have solar panels, savings can increase. Instead of exporting surplus solar electricity to the grid at 4 to 5p/kWh, your battery stores it for evening use. A 5 kWh box still has a 5 kWh ceiling. It will not match the annual kWh of a 10 to 15 kWh wall kit.
You don't need solar to start. A battery-only setup delivers the overnight-tariff return on its own, and you can always add solar later.
Save up to about £420 to £490 a year, best case
Join the waitlist for a Habo Energy 5 kWh EcoFlow STREAM. From £2,499 fully installed, electrician-wired.
Join the waitlist