Calculator Methodology & Data Sources

Technical assumptions, calculation models, and public research references

1. Solar Irradiance & Generation Assumptions

Annual electricity generation is calculated using standard UK regional irradiance benchmarks derived from the European Commission’s Photovoltaic Geographical Information System (PVGIS):

• South / South-East England: ~1,080 kWh per installed kWp
• Midlands, East Anglia & Wales: ~950 kWh per installed kWp
• Northern England & Northern Ireland: ~880 kWh per installed kWp
• Scotland: ~820 kWh per installed kWp

2. Self-Consumption & Battery Storage Ratios

In line with Energy Saving Trust research:

• Solar Only (No Battery): Modelled at ~30% to 35% household self-consumption of generated solar energy.
• Solar + 9.5kWh Battery: Modelled at ~75% to 80% self-consumption, capturing daytime surplus for evening usage.
• Solar + 13.5kWh Battery: Modelled at ~85% to 90% self-consumption with whole-home load coverage.

3. Pricing & Tariff Assumptions

Grid unit rates are modelled against prevailing UK energy price cap averages (~26.5p/kWh standard import rate). Export rates are modelled across standard Smart Export Guarantee (SEG) benchmarks (12p/kWh fixed) and smart dynamic battery arbitrage tariffs (blended 24p/kWh peak export with off-peak charging).

4. Property Value Research Reference

Academic studies (such as research published by Swansea University and data examined by the Urban Big Data Centre) indicate an association between solar panel installations and property price premiums of approximately 6.1% to 7.1%. However, because property value changes depend heavily on property type, local market demand, system ownership terms, and condition, property value increases cannot be guaranteed.