Solar Panel Payback Calculator UK — By Postcode

How this calculator works

Solar Payback by Postcode is a deliberately simplified, location-first version of our full Solar Panel Savings Calculator. The idea is to answer one question fast — "what's the payback in my area?" — without asking you to understand SCOP, SEG or self-consumption terminology up front. Enter a UK postcode, pick a system size, and the page pulls a representative PVGIS irradiance figure for your outcode and plugs it into the same underlying cash-flow model used on the full calculator. Everything else — £7,200 install cost, 27p/kWh import, 15p/kWh SEG export, 3,500 kWh/yr household use, 4%/yr electricity inflation — uses confident 2026 UK defaults.

PVGIS is the European Commission Joint Research Centre's open dataset, built from decades of satellite-measured solar radiation data. For a south-facing roof at around 35° tilt — the UK-typical pitch — it returns annual specific yield in kWh per kWp. We look up your outcode's representative coordinates, query PVGIS, and feed the number into the payback model. The difference between a cloudy 850 kWh/kWp in the Scottish lowlands and a sunny 1,035 kWh/kWp on the Sussex coast is roughly 22% more generation, which on the same 4 kWp system typically shortens payback by 12–18 months.

Common pitfalls and things people get wrong

• Postcode is a proxy, not a guarantee. We map your outcode (e.g. SW1A) to a representative latitude and longitude, then PVGIS quotes a yield for that point. If you live on a north-facing slope, behind a hill, or next to a large tree, your own yield can be 10–25% below the headline figure for your area.
• The default assumptions are friendly. We use £7,200 installed (a fair mid-market 2026 price for 4 kWp), 27p/kWh import (the current Ofgem cap ballpark), and 15p/kWh SEG (Octopus Outgoing-level). If your quote is £9,500 and your SEG is 5p, your real payback is longer than the headline — use the full calculator to model your own numbers.
• Regional cloud vs regional irradiance. Many people assume Glasgow is "hopeless" for solar. In reality, Glasgow at 850 kWh/kWp still generates meaningfully — a 4 kWp system puts out around 3,400 kWh/yr and saves a typical household £500–£600 in year one. Solar is worthwhile across the whole UK; it is just more-worthwhile in the south.
• Panel quality is flattened out. Modern Tier-1 panels all sit within a narrow band of real-world performance. The single biggest swing in yield for a given postcode is orientation and shading, not which brand of panel the installer proposes.

UK-specific context

The UK's retained VAT zero-rating on solar and battery installs runs to at least March 2027, which is a material saving versus the rest of Europe. Most UK DNOs (Distribution Network Operators) now permit up to 3.68 kW export per phase under G98 without prior approval — so a single-phase home can usually install any size system and export-limit to 3.68 kW in the inverter settings. If you want to export more than that, your installer applies under G99, which is routine but adds 4–8 weeks to commissioning. The SEG market is competitive: rates refresh roughly yearly, and switching export supplier is a 10-minute task.

When this isn't the right answer

This postcode tool is a quick-look. It does not let you model a battery, an east-west roof split, different household usage, time-of-use tariffs, or the impact of an EV. If any of those apply to you, hop over to the full Solar Panel Savings Calculator — same engine, more levers, more honest scenario comparison. And if you are in a flat with no south-facing roof, or considering ground-mount solar on a smallholding, please do not rely on an outcode-level yield number; get a site survey.

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