3kW sits at the lower end of what is now typically installed. It suits a smaller house, a smaller roof, or a household with modest electricity use.
Last reviewed 6 Nov 2026.
The basics
| System size | 3kW |
| Panels | around 8, depending on their wattage |
| Roof area needed | Roughly 14 to 17 square metres |
| Estimated generation | 2,550 to 3,000 kWh a year |
Generation assumes a reasonably oriented, unshaded roof. Yours will differ with orientation, pitch, shading and where you are in the country. See what affects output.
Panel count is not a useful comparison between quotes. Panel wattages vary enough that one installer’s ten panels can be another’s twelve for the same system size. Compare the size in kW and the generation estimate in kWh.
The grid connection point
It is also close to the 3.68kW grid connection threshold, which is why a lot of quotes land near this size: it connects under G98 with no prior permission needed.
See grid connection.
What it costs
A system of this size typically falls within the £6,600 to £8,400 range that covers most domestic installations, with a battery adding £3,500 to £5,500.
Prices do not scale neatly with size. Scaffolding, certification, network paperwork and most of the labour cost much the same whatever the system size, so a smaller system carries more of those fixed costs per watt. That is why stepping up a size often costs less than you would expect. See comparing system sizes.
VAT is currently 0% on installed solar until 31 Mar 2027.
Indicative ranges, last reviewed 6 Nov 2026. Only a quote is a price.
Is this the right size for you?
The generation figure is not the useful number. What matters is how much of it you use rather than export, because a unit used saves you about 26.32p and a unit exported earns roughly half that.
So this size suits you if it broadly matches your daytime consumption, or if you are adding a battery, an electric car or a heat pump, any of which raise how much you use.
Getting quotes
We are not taking quote requests at the moment. When you get quotes, ask each installer what this size would cost and what the next size up would add, because the marginal cost is usually the interesting number. Take the questions list with you.