System types
Four kinds of solar system, and what each does in a power cut
The parts are similar. How they are connected decides what you save and whether the lights stay on.
Type 1
On-grid solar, no battery
Panels and a grid-tied inverter. You use what you can as it is generated and export the rest.
- Typical cost
- £6,000 to £8,000 for 4 kWp, installed
- In a power cut
- Off
- Share of solar used at home
- About 30 to 50%
- Best for
- Lowest cost and a short payback
- Cheapest way into solar
- Few parts to go wrong
- A battery can be added later
- No power in a cut, even in sunshine
- Surplus is exported at a lower rate than you pay to import
- Little help on winter evenings
Type 2
Hybrid solar with a battery
One hybrid inverter manages the panels and a battery. Daytime surplus is stored and used in the evening.
- Typical cost
- £10,000 to £14,000 for 4 kWp with a battery
- In a power cut
- Off, unless backup is fitted
- Share of solar used at home
- About 60 to 80%
- Best for
- Homes out all day, time-of-use tariffs
- Much less bought from the grid
- Can charge on cheap overnight electricity in winter
- Most hybrid inverters can add backup later
- The battery adds roughly £2,500 to £6,500
- Payback is often longer than solar alone
- Many are installed with no backup at all: ask
Type 3
Hybrid with automatic switchover
The same hybrid system with a backup gateway. When the grid fails, the gateway isolates your building and the battery carries on.
- Typical cost
- A hybrid system plus £500 to £3,000 for the gateway and wiring
- In a power cut
- On, within seconds
- Covers
- Chosen circuits or the whole building
- Best for
- Homes and businesses with equipment that must stay on
- Nothing to do when the power fails
- Solar keeps charging the battery during the cut
- Lower bills every other day of the year
- Limited by the inverter's power: not every appliance at once
- Changeover is fast but rarely instant, so computers still want a UPS
- Needs extra earthing and network operator approval
Type 4
Fully off-grid
No grid connection. Panels charge a battery bank, and an inverter supplies mains power from it. This is how cabins, narrowboats and campervans run.
- Typical cost
- From about £2,400 in parts for a 16 kWh battery and 4 kW inverter, plus panels and fitting
- In a power cut
- Unaffected
- Sized for
- The darkest weeks of winter
- Best for
- Sites where a grid connection is impossible or very expensive
- No standing charge and no unit rate
- Works anywhere
- Scales from one panel on a van to a whole farm
- A December day gives roughly a fifth of a June day's solar
- Usually needs a generator or shore power in winter
- You are your own power company: you manage what runs when
Side by side
| On-grid | Hybrid with battery | Automatic switchover | Off-grid | |
|---|---|---|---|---|
| Lowers bills | Yes | Yes, more | Yes, more | No bills |
| Works in a power cut | No | Only if backup is fitted | Yes, automatically | Always |
| Earns from export | Yes | Yes | Yes | No |
| Battery | None | 5 to 15 kWh typical | 10 kWh or more typical | Sized for days |
| Typical installed cost | £6,000 to £8,000 | £10,000 to £14,000 | £10,500 to £17,000 | Varies widely |
Cost ranges are for a typical 4 kWp home system and were checked 12 November 2026. Your quotes will differ.