The Octopus Go maths for a battery without solar panels
On Octopus Go, electricity is cheap between 00:30 and 05:30 every night. A battery charges in that window and replaces electricity you would otherwise buy at the day rate. The saving is the gap between the two prices, every day.
Our worked figures are based on Octopus Go 12M Fixed (GO-FIX-12M-26-10-14, checked 15 October 2026): 9.4p per kWh overnight and 35.293p to 39.3081p per kWh at other times, depending on region. With a 5 kWh battery and an assumed 90% round-trip efficiency:
To deliver 5 kWh you buy 5 ÷ 0.9 = 5.556 kWh overnight, costing 52.22p. That 5 kWh is worth 176.47p to 196.54p at the day rate. Daily saving: about £1.24 to £1.44, or up to about £450 to £530 a year in the best case.
Octopus Go rates change when Octopus launches a new fix, so check the current rates for your region before you decide.
What that is worth as an interest rate
| Measure on £2,499 (best case, based on Octopus Go 12M Fixed (GO-FIX-12M-26-10-14), checked 15 October 2026) | Figure |
|---|---|
| Yearly saving | up to about £450 to £530 |
| Equivalent simple interest (yearly saving ÷ £2,499) | about 18.1% to 21.1% |
| Like-for-like annual return over EcoFlow's 10-year warranty | about 12.6% to 16.5% |
| Payback | about 4.7 to 5.5 years |
The like-for-like return is lower because the money is spent and the battery wears out, unlike a savings balance you get back. See home battery vs savings account for the workings.
When does a battery without solar not save money?
On a flat-rate tariff with no cheap period, a battery without solar will not reduce your bills: there is no price gap to use. If you use less than the battery's capacity outside the cheap window, you will also save less than the best case.
Home battery storage without solar: UK cost
Habo Energy installs a 5 kWh EcoFlow STREAM from £2,499, electrician-wired to your consumer unit. Installed batteries are zero-rated for VAT (0% VAT) until 31 March 2027, then 5%. For sourced prices and kit vs installed costs, see our home battery storage cost guide.
Home battery backup without solar
EcoFlow's UK STREAM pages say that during a power outage the STREAM 5000 switches to off-grid mode: the grid-connected port stops outputting, and the unit supplies power to loads connected to its own AC outlet, provided the battery has enough charge (EcoFlow STREAM 5000). For a single STREAM AC 5000, EcoFlow's FAQ gives 2,500W as the maximum off-grid output of that outlet (its spec table lists 3,000W off-grid AC output; we use the lower FAQ figure). So backup covers what you plug into the unit, not the whole home.
How long it lasts depends on what you plug in and how much charge is left. If backup matters to you, ask your installer what your setup will and will not cover.
How does a battery without solar work?
You need two things: a home battery with an inverter, and a time-of-use tariff. All-in-one units combine the battery and inverter in one box; EcoFlow says the STREAM host includes the battery and grid-tied inverter. For a full overview, see our guide to home battery storage systems.
Why choose a battery without solar panels?
Your roof might face the wrong way, be shaded, or be unsuitable for panels, or you might simply not want solar yet. A battery on a time-of-use tariff can save money without any panels.
Which tariffs work with a battery?
You need a tariff with a cheaper period. Octopus options include Octopus Go (cheap 00:30 to 05:30), Intelligent Octopus Go and Agile Octopus, which changes price every half hour. Check eligibility and current rates on each tariff page, or put your own rates into the savings calculator.
G98 and a battery without solar
G98 covers equipment up to 16 A per phase (about 3.68 kW on a single-phase supply), in total at the property; your installer fits it and notifies the network operator (G98 single premises guide). Anything bigger needs a G99 application first. EcoFlow lists a single STREAM AC 5000's grid-connected output as 2,500W and a single STREAM 5000's as 3,000W. Your installer confirms which route applies to your home. See our guide to G98 vs G99.
Can you add solar panels later?
It depends on the battery. EcoFlow lists the STREAM 5000 with four solar inputs (MPPTs), so panels can be connected later. Check the spec of the model you are quoted. See batteries with solar panels.
Renting, or in a flat?
If you rent or own a leasehold flat, check your tenancy agreement or lease and ask your landlord or freeholder before arranging a wired-in installation. A plug-in battery does not power the whole home. Our guide to battery storage for flats covers the options.
What to look for in a battery
- Usable capacity: match it to how much electricity you use outside the cheap window. See what size battery.
- Charge rate: check it can fill the battery within your tariff's cheap window.
- Backup: check exactly what the battery can supply in a power cut.
- Warranty: warranties vary by brand, so check years, cycles and end capacity.
Habo's approach: set and forget
Habo sets a timer schedule at installation: the battery charges in your tariff's cheap window and powers your home afterwards, so you do not need to manage it day to day.
Get home battery storage without solar
Habo fits a 5 kWh EcoFlow STREAM, electrician-wired to your consumer unit, from £2,499 installed. Not a plug-in battery. Best case up to about £450 to £530 a year, based on Octopus Go 12M Fixed (GO-FIX-12M-26-10-14), checked 15 October 2026, so real savings will be lower (see how we worked it out). Habo will try to serve anyone who registers in an area where we have an electrician. Join the waitlist. Nothing to pay today.
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