What is the solar sizing calculator?
How our free tool helps you work out how many solar panels your home needs, what size inverter to pair them with and how much you could save.
How to use the calculator
A step-by-step guide to entering your postcode, roof details, electricity usage and tariff to get a personalised solar system recommendation.
How we estimate generation
How we calculate expected annual generation using your location, roof pitch, orientation, shading and panel efficiency, based on real UK irradiance data.
Panel sizing explained
How we recommend the right number of panels based on your roof space, electricity consumption and whether you plan to add a battery or EV charger.
Inverter sizing explained
Why inverter size matters, how we match inverter capacity to your panel array and when a hybrid inverter makes sense for future battery storage.
Cost estimates & payback
How we estimate installed costs using real MCS installer data, what affects payback period and how export income under the SEG is calculated.
Self-consumption vs export
How we model the split between electricity you use directly and electricity you export, why self-consumption rate is the biggest driver of savings.
Adding a battery to your system
How the calculator models the impact of adding battery storage, the additional cost, improved self-consumption and effect on payback period.
Limitations & next steps
What the calculator cannot account for, including exact shading, structural loading and DNO constraints, and why a professional site survey is the next step.
Frequently asked questions
Common questions about the solar sizing calculator, including accuracy, data sources, whether it works for flat roofs and how to interpret the results.