What battery storage does for your solar system
Without a battery, the average Midlands solar install exports 60-70% of what it generates to the grid — earning a few pence per kWh on the Smart Export Guarantee — while you continue to buy the evening peak from the grid at 28-31p/kWh. The economics don't quite balance.
Adding a 5-10kWh battery stores midday surplus and discharges it at evening peak. Self-consumption jumps to 75-85% on a typical system. The maths: a 4kW + 5kWh combination saves roughly £900-£1,100 per year vs grid-only, vs around £550-£700 for solar-only.
The second use case — arguably more valuable in 2026 — is off-peak arbitrage. Octopus Go and Intelligent Octopus charge at around 7p/kWh between 23:30-05:30. The battery charges off the grid overnight, then discharges through the morning and evening peaks. Even without solar, this saves a typical 4-person household £400-£600 a year on electricity. Combined with solar, the savings compound.
Tesla Powerwall or Fox-ESS — which?
Tesla Powerwall 3 (13.5kWh, integrated inverter): the gold-standard if you want one device that does it all. Powerful (11.5kW continuous), elegant app, whole-home backup capable. Premium price — typically £9,500-£12,000 installed.
Fox-ESS EP5 / ECS: strong residential performer, large stackable range, slick app. Lower price than Tesla, similar capability per kWh. £4,800-£8,000 installed.
We model both in your quote with payback projections, so you can pick the one that suits your priorities — not what we'd push on margin.
Retrofit battery to an existing solar system
If you already have solar panels (Midlands homes that fitted between 2014-2022 are particularly common retrofit candidates), we can add a battery without replacing your existing inverter. Two patterns:
AC-coupled: a separate battery inverter sits alongside your existing solar inverter. Works with any solar system, regardless of brand. Slightly less efficient (~5% round-trip loss vs ~3% DC-coupled) but maximum flexibility.
DC-coupled / hybrid replacement: we replace your existing inverter with a hybrid (solar + battery in one). Better efficiency, fewer devices, single warranty. Cost-effective if your existing inverter is approaching 10+ years.
MCS battery certification applies to retrofits as well as new installs — qualifying you for 0% VAT until 31 March 2027.
How long does a battery installation take?
For a typical retrofit on an existing solar system, allow 1 day on site. For a new combined solar + battery install, 1-2 days total. We handle DNO notification (G99 for batteries over 16A), AC isolation, EPS (Emergency Power Supply) wiring if backup is included, app configuration, and integration with off-peak tariffs.
MCS battery certification is issued within 7 days of commissioning. SEG application updates within 6 weeks if you're adding a battery to an existing solar system (your generation profile changes).
EV charging and battery storage together
If you have a Zappi, Ohme, Myenergi EV charger, or a Pod Point Solo, we configure them together with your battery and solar so the system intelligently routes:
- Solar surplus → first to home loads, then to battery (until full), then to EV (smart charge from solar) - Off-peak grid → top up the battery between 23:30-05:30 - Peak grid avoidance → battery discharges to home + EV during 16:00-19:00
The right tariff (Intelligent Octopus, EDF GoElectric) means the EV often charges at ~6p/kWh — vs ~50p/kWh on petrol-equivalent costs for an ICE car. We've done dozens of these integrated installs across Birmingham, Coventry and Leicester suburbs.