Best Solar Battery UK —
Compared Honestly
Tesla Powerwall, Sigenergy SigenStor, Fox ESS and ECOFlow — the battery storage brands we actually install, compared on capacity, installed price and warranty. Features and fit, not sales talk.
Why "Best" Depends on Your Home
Every battery brand review online claims a different winner. In reality, the right battery depends on four things: your budget, the capacity you need, whether you're retrofitting to existing solar or starting fresh, and how much you value a polished app versus straightforward value for money.
We install Tesla Powerwall, Sigenergy SigenStor, Fox ESS and ECOFlow — so we don't need to push one brand over another. This page sets out what each is actually good at, with the capacities and installed prices we quote on real jobs. There are no guaranteed savings figures here — your usage, roof and existing setup all affect the numbers, and your free survey will give you exact ones.
Solar Battery Brands Compared
A feature-by-feature look at the four brands we install most, based on the systems we actually quote.
| Brand | Capacity range | Installed cost from | Battery warranty | Best for |
|---|---|---|---|---|
| Tesla Powerwall 3 | 13.5kWh per unit, stackable to 40.5kWh | £7,200 | 10 years (70% capacity retention) | Premium all-in-one system, integrated inverter, strongest app |
| Sigenergy SigenStor | 6–10kWh per module, stackable well beyond 30kWh | £5,400 | 10 years | Flexible modular sizing, staged installs, V2H-ready |
| Fox ESS | 5.76–11.52kWh per module, expandable | £4,400 | 10 years (inverter warranty varies by model) | Best value for straightforward storage |
| ECOFlow | Modular AC-coupled units, sized to your setup | Priced on survey | Varies by model — confirmed at quote stage | Retrofitting without touching your existing inverter |
Installed cost is our current "from" price for the smallest module of each brand, fully installed. Larger capacities cost more — see the model-by-model pricing below or price your own system on the calculator. ECOFlow pricing depends on the specific model and configuration, so we quote it during survey rather than advertise a "from" price. Figures are not guaranteed savings; they reflect installed cost only.
Model-by-Model Installed Pricing
The same figures we quote on our battery storage page, broken out by model. For how prices move with battery size across the whole market, see home battery costs by size. If you are comparing a supplier offer, read our take on Octopus battery storage.
| System | Capacity | Installed cost |
|---|---|---|
| Fox ESS EP6 | 5.76 kWh | From £4,400 |
| Fox ESS EP12 | 11.52 kWh | From £5,300 |
| SigenStor BAT 6.0 | 5.84 kWh | From £5,400 |
| SigenStor BAT 10.0 | 8.76 kWh | From £5,900 |
| Tesla Powerwall 3 | 13.5 kWh | From £7,200 |
Prices include supply, installation and commissioning of a standalone battery. Combined solar and battery packages are usually better value — see Solar + Battery Packages. ECOFlow is quoted individually as capacity and configuration vary by job. Your free survey will confirm the exact figure for your property.
What Each Brand Is Actually Good At
Tesla Powerwall 3 — the polished all-in-one
13.5kWh of usable capacity with a built-in hybrid inverter, so solar connects directly (DC-coupled) rather than through a separate box. The Tesla app is the cleanest and most intuitive we install, and the brand recognition is unmatched. The trade-off is price — expect to pay more per kWh than the alternatives below.
Tesla Powerwall Installation →- 13.5kWh usable capacity, stackable to 40.5kWh
- Integrated inverter — fewer components on install day
- 10-year warranty, 70% capacity retention guaranteed
- From £7,200 installed
Sigenergy SigenStor — the flexible modular system
SigenStor is built around small, stackable modules, so you can size a system precisely to your usage and add another module later without replacing anything. It carries the same 10-year warranty as Powerwall, costs less per kWh, and is V2H-ready if you're planning to add an EV charger that can discharge back into the home.
SigenStor Installation →- Modular from 6kWh, stackable well beyond 30kWh
- 10-year warranty on battery and hybrid inverter
- Vehicle-to-home (V2H) ready
- From £5,400 installed
Fox ESS — the value pick
Fox ESS is a solid, no-frills battery with LFP chemistry and a 10-year battery warranty when registered via the Fox ESS app, usually the cheapest way into 5.76–11.52kWh of storage. The hybrid inverter carries 10 years on the same terms, which is worth checking when comparing quotes. Good if you want reliable storage without paying for extras you won't use.
Read Our Fox ESS Review →- 5.76–11.52kWh per module, expandable further
- 10-year battery warranty, LFP chemistry
- Lowest "from" price of the brands we install
- From £4,400 installed
ECOFlow — the retrofit-friendly option
ECOFlow's AC-coupled units connect on the output side of your existing solar setup, so we don't need to touch or replace your current inverter. That makes it one of the simplest ways to add storage to an existing solar installation. Capacity and pricing are configured per job rather than sold as a single fixed model, so we'll size and quote it during your survey.
Battery Retrofit Options →- AC-coupled — no inverter swap required
- Well suited to retrofitting existing solar
- Modular, sized to your setup
- Priced individually at survey
Which One Should You Choose?
Want the most polished experience?
If the app, the design and the brand matter as much as the numbers, and budget is a secondary concern — Tesla Powerwall 3 is the strongest all-round choice we install.
Want to size it precisely and expand later?
Sigenergy SigenStor's modular design means you can start smaller and add a module in future without replacing what you already have. Also the best fit if you're planning V2H.
Value for money is the priority?
Fox ESS gives you solid LFP battery technology and a 10-year warranty at the lowest installed cost of the four brands, without cutting corners on the storage itself.
Retrofitting to existing solar?
ECOFlow's AC-coupled design means no changes to your existing inverter. If you'd rather keep your current setup untouched, this is usually the simplest route in.
Not sure which category you fall into? That's exactly what the free survey is for — we'll look at your roof, existing setup (if any) and usage, then recommend a specific model and give you a fixed-price quote.
Do You Need Solar Panels First?
No. Any of the four brands above can be installed as a standalone battery, charging from the grid overnight on a cheap-rate tariff and discharging during expensive peak periods. A standalone battery can also provide backup power on systems with that functionality.
That said, if you're planning solar panels at some point too, installing both together is usually more cost-effective than adding a battery afterwards — one set of scaffolding, one installation day, and a system designed to work as a unit from the start. See our Solar + Battery Packages for combined pricing, or our battery retrofit page if you already have solar and want to add storage.
Best Solar Battery UK — FAQs
There isn't one battery that's best for every home — it depends on your budget, the capacity you need, and whether you want the most polished all-in-one system or the best value per kWh. Tesla Powerwall 3 leads on app experience and integrated design. Sigenergy SigenStor offers the most flexible modular sizing. Fox ESS is usually the best value for straightforward storage. ECOFlow suits retrofits where you don't want to touch your existing inverter. We install all four and will recommend the right fit during your free survey.
A home battery typically costs from £4,400 installed depending on capacity and brand (5.8–17kWh+ is the common range). Fox ESS starts lowest, Sigenergy SigenStor and Tesla Powerwall 3 cost more but offer larger single-unit capacity or a more integrated system. Combined solar and battery packages are often better value than adding a battery later — see our solar and battery packages page for current pricing.
Yes. A standalone battery can charge from the grid overnight on a cheap-rate tariff and discharge during expensive peak periods, with no solar required. It can also provide backup power on systems with that functionality. We install standalone batteries as well as combined solar-and-battery systems.
Tesla Powerwall, Sigenergy SigenStor and Fox ESS batteries all carry a 10-year manufacturer's warranty on the battery itself. Terms vary by brand — Fox ESS gives 10 years when the unit is registered via the Fox ESS app, which is not automatic, so it's worth checking what's included when you compare quotes. We'll confirm the exact warranty terms for your chosen system during your survey.
We install Sigenergy, Fox ESS, ECOFlow, Tesla Powerwall, and other quality battery systems. The right choice depends on your existing setup, required capacity, and budget. We'll recommend the best option during your free survey — not the biggest or most expensive system we can sell you.
Ready to Compare Quotes?
Price your own system on the calculator, or see the full battery storage overview and combined solar + battery packages.
How battery storage works, sizing, payback and tariffs
Merged from our battery storage guide. For the related topics with pages of their own, see retrofitting a battery to existing solar, AC-coupled vs DC-coupled, and battery storage without solar.
How Home Battery Storage Works
A home battery system stores electricity so you can use it when you need it, rather than when it's generated or cheapest. There are two main use cases:
With solar panels: Your solar panels generate electricity during daylight. Without a battery, any surplus you don't use immediately gets exported to the grid — often at a low rate (typically 4–15p/kWh via the Smart Export Guarantee). A battery captures that surplus so you can use it in the evening, overnight, or on a cloudy day instead of buying from the grid at 24–35p/kWh. The difference between what you'd pay (buying) and what you'd receive (exporting) is your saving.
Without solar panels: You charge the battery on cheap off-peak electricity (e.g. 7–15p/kWh on Octopus Agile overnight) and use it during expensive peak hours (typically 4–7pm at 30–38p/kWh). This is called grid arbitrage and can save £280–£650/year depending on battery size and tariff spread.
In both cases, the battery connects to your home via a hybrid or battery inverter. A battery management system (BMS) inside the unit protects the cells, manages charge cycles, and communicates with any smart tariff or solar forecast system.
What Size Battery Do You Need?
Battery sizing depends on three things: how much solar you generate, how much electricity you use in the evening and overnight, and whether you want backup capability. Most batteries do nothing in a power cut unless they are fitted with an EPS output or a backup gateway, so check what backup really involves before you choose.
| Home type | Daily evening use | Solar system | Recommended battery |
|---|---|---|---|
| 1–2 bed flat / low usage | 2–3 kWh | 2–3 kWp | 2.9–5 kWh |
| 3 bed semi — average usage | 3–5 kWh | 3.5–4.5 kWp | 5–7.5 kWh |
| 4 bed detached — higher usage | 5–8 kWh | 5–6.5 kWp | 10 kWh |
| 4+ bed with EV or heat pump | 8–15 kWh | 6–10 kWp | 13.5–20 kWh |
Don't over-size against your solar. A 10 kWh battery on a 2 kWp south-facing roof in Milton Keynes will only fill to about 60% on a good summer day — and barely charge at all in December. Match battery capacity to roughly 1.5–2× your typical daily solar surplus.
Battery Storage Payback Period
Payback depends on the installed cost and your annual saving. For most UK households with solar:
- 5 kWh battery at £3,000 saving £400/yr → 7.5 year payback
- 10 kWh battery at £5,000 saving £650/yr → 7.7 year payback
- 13.5 kWh Tesla Powerwall 3 at £9,500 saving £800/yr → 11.9 year payback
LFP (lithium iron phosphate) batteries like the Fox ESS ECS series are warranted for 6,000 cycles over 10 years — and typically last 15–20 years in real-world use. So even a 10-year payback leaves 5–10 years of free savings.
Where people go wrong: sizing the battery too large for their solar system (a 10 kWh battery on a 2 kWp system will rarely fill up in summer and sits empty in winter), or buying on Agile and not actually shifting usage. Battery payback is real but requires the right setup.
Best Energy Tariffs for Home Battery Owners
Your tariff choice has as much impact on your savings as the battery itself. Standard variable tariffs give you some benefit from solar self-consumption, but time-of-use tariffs unlock significantly more:
| Tariff | Off-peak rate | Peak rate | Export rate | Best for |
|---|---|---|---|---|
| Standard variable | ~26p/kWh (flat) | ~26p/kWh (flat) | 4–15p (SEG) | Solar self-consumption only |
| Octopus Go | ~9p/kWh (12am–5am) | ~30p/kWh | ~15p (SEG) | EV owners + battery |
| Octopus Flux | ~17p/kWh (off-peak) | ~34p/kWh (peak) | ~17p (off-peak export) | Solar + battery (best all-round) |
| Octopus Agile | Varies: 5–20p/kWh | Varies: 25–60p/kWh | ~15p (SEG) | Tech-savvy users, automation |
For most battery owners with solar, Octopus Flux is the standout tariff — it pays you more for exporting during peak hours and charges less for importing off-peak. Your battery can charge cheaply overnight and you export solar surplus at a better rate during the day. It requires a smart (SMETS2) meter — if you don't have one, Octopus will install it free.
Read more on this
- how home battery storage works, and what it costs
- our full Fox ESS battery review
- the SigenStor reviewed
- our Powerwall 3 review
- what a Tesla Powerwall 3 actually costs installed
- AC-coupled vs DC-coupled batteries
- fitting a battery without solar panels
- solar vs battery storage — do you need both?
- alternatives if you're moving away from GivEnergy
Get a Free Battery Storage Quote in Milton Keynes
Tell us which brand appeals, or let us recommend one after a free survey. Either way, you'll get a fixed-price quote with no guesswork.
Or email info@depthoflight.co.uk | Send a message
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