Do you need a battery for plug-in solar? The honest UK guide
30 August 2026 · Guide
The most common question after "is it legal?" is "do I need a battery?" The short answer: no - but it depends how much of your solar you want to use yourself. Here is the honest breakdown.
How plug-in solar works without a battery
Without a battery, the system is simple:
- Panels generate power during daylight hours
- Your home uses it first - running the washing machine, kettle, fridge, TV
- Anything you don't use flows back to the grid
Typical self-consumption is 30-40% without a battery. If you work from home, it can reach 45-55% because you're using power as it's generated. If you're out all day, it can drop to 15-25%.
What a battery changes
A battery stores the surplus you would otherwise export, and releases it in the evening when your solar has stopped generating but your usage peaks. With a battery, self-consumption typically rises to 70-80%.
In financial terms, every kWh you store and use yourself is worth your full electricity rate (~24.5p), instead of the 4-15p you'd get exporting it. That gap is what makes batteries attractive - but the battery itself costs money.
What batteries cost
- Small battery (1-2 kWh): EcoFlow STREAM AC Pro 1.92 kWh - £699-£899
- Medium (3-4 kWh): EcoFlow STREAM Ultra 1.92 kWh with panels, or Ultra X 3.84 kWh - £1,299-£1,649
- Large (expandable): stackable systems up to 23 kWh - from £1,999+
Battery chemistry is lithium iron phosphate (LiFePO4), typically rated for thousands of cycles - 10+ years of daily use is realistic, though warranties are usually 5 years.
The maths: when a battery pays off
Let's compare an 800W kit in southern England with and without a 1.92 kWh battery:
With 1.92 kWh battery: ~800 kWh/year, 75% self-consumed → saves roughly £160-£180 a year. Kit + battery £1,300-£1,700 → payback 8-10 years.
On pure payback, the no-battery option usually wins. The battery adds comfort and evening independence, but extends payback by several years. Where batteries shine: time-of-use tariffs (charging the battery cheaply overnight, though plug-in systems can't do this from the grid - only from solar), and homes that use a lot of evening power.
Our advice
- Start without a battery if you're on a budget or want the fastest payback. Most expandable kits let you add one later.
- Add a battery if you use lots of power in the evening (cooking, heating, EV charging at home) and want to shift your solar into those hours.
- Consider it from day one if you're out during the day and have a good sunny position - without a battery, most of your solar would go to the grid at low export rates.
- Check if your kit is expandable before you buy - EcoFlow STREAM, Anker SOLIX and UKSOL's newer kits all support adding storage later.
Battery safety and rules
- Buy a battery with proper UK certifications - don't import uncertified cells
- Batteries must be installed per the manufacturer's instructions; keep them dry and ventilated
- The 800W AC cap applies to what flows into your home circuit, regardless of battery size
- Your G98 notification still applies - file it before connecting
Want to see the numbers for your own home? Try the savings calculator - toggle the battery option to compare with and without storage.