Solar Power Is A Game Chnager

Solar Roof-to-Savings Calculator

An investment that saves on energy costs.

Solar Roof-to-Savings Calculator

Estimate array size, annual generation, self-consumption, export revenue, £ savings, CO₂ cuts and simple payback.

Usable roof area (m²) Tip: exclude skylights, plant, heavy shade. Usable coverage (%) How much of the roof can actually take panels. Panel power density (Wp per m²) Modern modules: ~170–200 Wp/m². Specific yield (kWh per kWp per year) UK typical 850–1100, adjust for tilt/orientation. Annual electricity use (kWh) Your site’s total consumption. Daytime use fraction (%) Share of use occurring during solar hours. Import tariff (£/kWh) Export tariff (£/kWh) CO₂ factor (kg/kWh) Capex ( £ / kWp ) Indicative commercial turnkey cost. Battery boost (optional) Simple planner uplift. We’ll size storage properly in a survey.

System size

– kWp

Panels area used: – m²

Annual generation

– kWh

Specific yield: – kWh/kWp

Self-consumed

– kWh

Exported: – kWh

Annual benefit

Bill offset: £–

Export revenue: £–

Total: £–

CO₂ avoided

– kg / yr

Payback

–

Capex est.: £–

Planner notes

Generation ≈ kWp × specific yield. Self-consumption limited by your daytime usage.
Battery boost is a simple uplift (+10–20%) to show potential shift; actual results depend on storage size and profile.
For LED + Solar synergy, reduce annual usage first with our lighting calculators—then re-run solar sizing.

Estimates for planning only. Root3 will verify roof structure, shading, electrical capacity, and economics in a site survey.

FAQ’s

Below are common questions about how the calculator estimates system size, savings, and payback—so you know exactly what’s driving your results.

How accurate are these estimates?

They’re planner-level figures. Results depend on your roof coverage, shading, panel density, specific yield, tariffs, and how much energy you use during daylight. We confirm all assumptions with a site survey (orientation, tilt, shade, electrical capacity) before final proposals.

What should I enter for “Specific yield” and “Daytime use”?

Typical UK specific yield is 850–1,100 kWh/kWp/year (adjust up/down for tilt/orientation and shading). Daytime use varies by site—40–70% is common for 9–5 operations. If you have half-hourly data, use it to refine your daytime percentage.

How do import and export prices affect savings?

Your biggest gain usually comes from offsetting imported electricity (import tariff). Any excess you don’t use on site is exported and earns an export rate (e.g., SEG). Try different tariff values in the inputs to see how total annual benefit and payback respond.

What does the “Battery boost” do?

It simulates how storage can increase self-consumption (e.g., +10–20%) so more solar displaces grid energy. It’s a simple uplift for planning; actual results depend on battery size, load profile, and control strategy. We size storage properly after a survey.

Still have more questions?

Prefer a tailored quote? Speak to a lighting engineer. We offer a free lighting survey.