Solar Panel Cost Calculator UK 2026
A useful solar panel cost calculator starts with the full installed quote, not just the panel price. System size, roof access, scaffolding, inverter choice, electrical work, battery storage and installer quality all change the result.
Energy Saving Trust currently describes an average home solar panel system as around £6,100, with domestic systems generally around 3.5kWp. Treat that as a planning anchor, not a promise that your roof will cost the same.
Cost calculator inputs to check
| Input | What to enter | What to verify |
|---|---|---|
| Solar-only system | The full installed quote including VAT treatment. | Scaffolding, inverter, monitoring, warranty and VAT treatment. |
| Battery storage | The installed battery add-on, if you are comparing one. | Usable kWh, cycle warranty, backup capability and install timing. |
| Generation estimate | Installer kWh/year estimate, or a conservative PVGIS check. | Roof orientation, shading, pitch, array layout and local weather data. |
| Cost per kW | Total solar-only cost divided by system size in kW or kWp. | Whether two quotes are using the same system size and inverter output. |
The simple cost formula
Solar cost per kW = installed solar-only quote ÷ system size. Payback years = total upfront cost ÷ annual benefit.
What makes one quote more expensive?
- Roof complexity: awkward access, slate roofs, multiple roof faces or roof repairs can increase labour and scaffolding costs.
- Equipment choices: panel brand, inverter type, optimisers, micro-inverters, battery brand and monitoring all change the quote.
- Electrical work: consumer unit changes, long cable runs, DNO work and export-limiting equipment can add cost.
- Aftercare: workmanship warranty, monitoring support and a responsive installer are worth comparing, not just the headline price.
VAT and battery cost notes
GOV.UK VAT Notice 708/6 says a temporary zero rate applies to the installation of specified energy-saving materials from 1 May 2023 to 31 March 2027. The notice includes photovoltaic panels, and from 1 February 2024 it also includes batteries for storing energy converted from electricity when the conditions are met.
Energy Saving Trust says battery storage costs depend on type and size, with a 5kWh battery system around £4,600 and wider costs ranging from £1,500 to £10,000. If your quote includes a battery, compare the battery's extra cost against the extra annual benefit, not just the combined system payback.
How to compare quotes fairly
- Compare the same system size in kWp and the same battery capacity in kWh.
- Ask for the annual generation estimate and the assumptions behind it.
- Check panel, inverter, battery and workmanship warranty periods separately.
- Confirm whether the installer is MCS certified if you want SEG export payments.
- Enter each quote into the calculator and compare payback and 20-year net value.
Using costs in the calculator
If you have no quotes yet, use a mid-range planning figure to understand sensitivity. Once quotes arrive, rerun the numbers. A cheaper system is not automatically better if generation assumptions are optimistic or the warranty support is weak.
For each quote, run three cases: the installer's generation estimate, a 10% lower generation case, and a battery case only if the battery cost and usage pattern are realistic.
Next: use the calculator · understand payback · compare solar prices · compare battery impact