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 July 2026 price cap (26.11p/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 26.11p/kWh (Ofgem July 2026 price cap), SEG export rate 12.5p/kWh. Grid electricity saved is worth roughly 2× more than electricity exported.
Realistic Self-Consumption
Without battery: 30% self-consumption assumed (industry standard for average household). With battery: 70% self-consumption. 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 | 26.11p/kWh (Ofgem July 2026 cap) | Ofgem price cap, 1 July – 30 September 2026 |
| Smart Export Guarantee rate | 12.5p/kWh | Average SEG rate across major suppliers, March 2026 |
| Self-consumption (no battery) | 30% | Industry standard for a working household |
| Self-consumption (with battery) | 70% | Typical result with 9.5kWh battery + average evening use |
| CO₂ factor | 0.233 kg/kWh | DESNZ UK grid carbon intensity, 2025 |
| EV additional saving | ~£200/yr | Based on 3,000 miles/year charged from solar at 4 miles/kWh |
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 30% of what it generates and exports the rest at a fraction of what it pays to buy back. A battery pushes that to roughly 70%. 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