Solar PV Calculator
Enter your site dimensions, postcode, orientation, pitch and electricity use to get a practical early-stage estimate of likely solar PV size, annual generation and indicative on-site use.
A Simple Early-Stage Solar Estimate
This calculator is intended as an early-stage guide. It gives a high-level estimate only and does not replace detailed design, structural review, shading analysis, electrical assessment or a full site survey.
It can be used for both roof-mounted and ground-mounted solar PV. The calculation allows for a practical area utilisation factor to reflect spacing, edges, access margins and layout constraints.
It also includes a simple electricity demand profile estimate so that likely direct solar use, export and battery suitability can be considered at outline stage.
Enter Your Site and Usage Details
Calculation Notes
This is a guide only and not a final design output.
Usable layout area can reduce materially due to spacing, edge setbacks, access zones, structure and practical module arrangement.
Demand profile outputs are based on generic usage patterns and do not replace interval meter data analysis.
Shading, electrical design, export limits, DNO constraints and detailed battery design are not included in this outline estimate.
Monthly Generation vs Demand
Orientation Comparison
Battery Sizing Guidance
Suitability: –
Suggested range: –
What This Calculator Assumes
This calculator assumes that around 80% of the stated area is usable for solar modules once practical layout allowances are made. It also assumes a broad modern module density of approximately 0.20 kWp per square metre of usable area.
The location-based base yield is then adjusted by simple factors for orientation and pitch or tilt to give a high-level UK-style indication of performance. It is not a substitute for measured irradiation data, structural review or detailed design software.
Electricity demand results are based on generic monthly and daytime matching profiles for the selected usage type. Where annual spend is entered instead of annual kWh, consumption is estimated using a simple assumed electricity rate.
How to Use the Result Sensibly
A useful solar estimate is one that helps narrow down whether a roof or site may be worth pursuing. It should not be treated as a final generation commitment.
Real layouts can change due to rooflights, access zones, edge setbacks, ground constraints, inverter strategy, structural limits, shading and grid constraints. These factors can materially affect the final design.
The usage and battery outputs are especially useful as screening tools, helping to show whether solar is more likely to be self-used on site, exported, or strengthened by storage.
Supporting Pages
Continue with the wider design and energy-use considerations around solar PV and storage.
Need a Proper Solar Design Review?
This calculator is a starting point only. SJ1 Renewables can provide a full system design, generation modelling and project review.