What do you get for the price?
A compliant kit is sold as a complete set. Each ENA register entry covers the whole kit configuration, not just the inverter. The Interim Product Specification (IPS) sets out what it includes:
- Panels: up to 2,000 W in total, no more than four modules (IPS §4.1, §4.2.2).
- A microinverter with an AC output of no more than 800 W (SI 2026/848).
- A moulded BS 1363 plug with a fuse of no more than 5 A, on a lead that goes straight into a fixed socket (IPS §6.2.3).
- Mounting hardware, which must be reversible and non-permanent (IPS §5.5.1). Some kits include a balcony, wall or ground frame; others sell it separately.
- A warning label to fix near your consumer unit (IPS §8.2.3.1).
Loose parts are not a plug-in kit
A standalone microinverter or a pile of loose panels won’t be listed as Compliant, however cheap it is. See the compliance checklist.
What extra costs should you check?
- Mounting, if it isn’t included or doesn’t suit your balcony, wall or garden. See mounting.
- An electrical check or upgrade. Homes with older fuses and no RCBOs should be checked and upgraded by an electrician (IPS §8.3.2, footnote 9). For kits with more than 960 W of panels, manufacturers must advise you to “consider professional assessment” of your wiring (IPS §4.1). See sockets and wiring.
- An outdoor socket, if you’d need one. It must be rated at least IP55 (IPS §4.2.3), and fitting one is electrical work.
- Delivery, which some listings include and others don’t.
Planning permission usually isn’t a cost: in England, a setup within permitted development needs no application. See planning permission.
Cost per watt or cost per kWh?
Cost per watt (price ÷ panel watts) is quick, but it misleads in two ways:
- From about 1.2 kW of panels, the 800 W inverter cap starts to clip output, so extra panel adds less than the wattage suggests (see how much electricity).
- It ignores where the panels go. A vertical balcony kit makes about a quarter less than the same kit tilted at 35°.
Cost per kWh allows for both.
How to work out cost per kWh
- Get year-one output. Take the kit’s first-year output for your location and angle from the calculator.
- Convert to ten years. Multiply by 9.78. That’s ten years with output falling 0.5% a year, our standard ageing assumption.
- Divide. Divide the price by the ten-year figure.
Worked for our reference kit (0.88 kWp, two panels of about 440 W, PVGIS 2005–2023 averages):
| Setup | Year-one output | Ten-year output | Cost per kWh, per £100 of price |
|---|---|---|---|
| London, 35° south | 897 kWh | 8,771 kWh | 1.14p |
| Manchester, 35° south | 780 kWh | 7,627 kWh | 1.31p |
| London, vertical south | 654 kWh | 6,395 kWh | 1.56p |
Multiply the last column by the kit price in hundreds of pounds. A £500 kit in London at 35° works out at 5 × 1.14p = 5.7p per kWh generated.
What price pays back within ten years?
You only save on electricity you use yourself. Surplus exported power usually earns nothing (see export). So compare the price with the ten-year value of self-used electricity.
At the October–December 2026 GB average cap of 26.32p/kWh (Ofgem) and medium daytime use (50% of output used at home):
| Setup | Ten-year self-used | Value at 26.32p |
|---|---|---|
| London, 35° south | 4,385 kWh | £1,154 |
| Manchester, 35° south | 3,813 kWh | £1,004 |
| London, vertical south | 3,197 kWh | £842 |
A kit priced below that figure pays for itself within ten years in that setup, if the unit rate stays the same.
- With low daytime use (33%), the London 35° figure drops to £762.
- With high use (63%), it rises to £1,454.
- Regional rates for October–December 2026 run from 25.36p to 27.86p.
Is a bigger kit better value?
Not always. The second panel is worth less than the first, because it adds output at the same sunny hours when your daytime use may already be covered. See 400 W vs 800 W.
You can't add a second kit later
The network rules allow only one plug-in device per household (Ofgem, G98 Issue 2 Amendment 1). Choose the size you want now.
What to do next
- Compare current prices on in stock (Compliant kits only by default).
- Get your own output figure from the calculator.
- Read is it worth it for payback in months per £100.
