Solar Panel & Battery Calculator
Estimate what solar, a battery, or both would do for your home in 2 minutes. No contact details needed — just enter a few details below.
Calculations use real Milton Keynes solar yield data (950 kWh/kWp/year) and the Ofgem price cap for 1 October – 31 December 2026 (26.32p/kWh).
How the Calculator Works
Transparent methodology — no black box estimates.
Real MK Solar Yield Data
Uses 950 kWh/kWp/year — the actual annual yield for Milton Keynes and surrounding areas, not a national average. South-facing is the 100% baseline; east/west drops to 85%; north drops to 65%.
Current Energy Prices
Savings calculated at 26.32p/kWh (Ofgem price cap, 1 October – 31 December 2026) and an export rate of 12p/kWh. Grid electricity saved is worth roughly 2× more than electricity exported.
Realistic Self-Consumption
Without a battery we assume 40% of what you generate is used in the house. With one, that rises to between 62% and 86% depending on the battery size. The difference explains most of the battery saving.
Calculator Assumptions
All inputs are visible and adjustable. Your precise quote will use actual measurements from your property.
| Variable | Value Used | Source |
|---|---|---|
| Solar yield (MK) | 950 kWh/kWp/year | PVGIS / SAP calculations for MK1 postcode area |
| Grid electricity rate | 26.32p/kWh | Ofgem price cap, 1 October – 31 December 2026 |
| Smart Export Guarantee rate | 12p/kWh | Octopus Outgoing fixed rate since 1 March 2026; other suppliers vary |
| Self-consumption (no battery) | 40% | Typical for a household that is home some of the day |
| Self-consumption (with battery) | 62–86% | Rises with battery size: about 66% at 6kWh, 74% at 10kWh, 82% at 13.5kWh |
| CO₂ factor | 0.177 kg/kWh | DESNZ 2025 greenhouse gas conversion factors, UK electricity |
Already Have Solar? Use the Battery-Only Mode
You do not need to model a whole new system to find out what storage is worth.
Retrofit to Existing Panels
If your panels are already up, the calculator will price a battery on its own. Most retrofits are AC-coupled, which means the battery sits alongside your existing inverter rather than replacing it.
Where the Saving Comes From
Without storage a typical household uses about 40% of what it generates and exports the rest at a fraction of what it pays to buy back. A battery pushes that to between 62% and 86%. That shift is most of the saving, not extra generation.
The Tariff Matters More Than the Battery
Payback figures elsewhere often assume an export tariff you are not on. Change the numbers here and you will see how much your rate moves the answer — it is usually the biggest single variable.
Ready to Get an Accurate Quote?
The calculator gives you a strong indication. A free home survey takes it further — precise roof measurements, shading assessment, and a fixed price in writing.
No obligation • Fixed pricing • MCS & NAPIT certified • Based in Milton Keynes