Solar calculator

Estimate your system size, electricity savings, payback period and carbon reduction from your monthly bill — calculated instantly in your browser with WebAssembly, with nothing sent anywhere.

Your electricity use

Average monthly bill (THB) Check your electricity bill (an average of the last 3–6 months is more accurate).

Installation region

Peak sun hours per day

Electricity rate (THB/kWh)

Sun hours are set automatically by region and can be edited.

Installed cost per kWp (THB)

Panel power each (watts)

Analysis period (years)

Advanced settings

Panel degradation (% per year)

Electricity price rise (% per year)

Performance ratio 0.50 – 0.95 · includes inverter, heat, wiring and dust losses

Your estimate

Recommended system size

– kWp

Number of panels: – panels
Roof area: ≈ – m²
Monthly electricity use: – kWh

Annual generation: – kWh
Annual bill savings: –
Estimated system cost: –
Payback period (simple): –
Total savings over 25 years: –
Return on investment (ROI): –
CO₂ cut per year: – tonnes
CO₂ cut over lifetime: – tonnes
Equivalent trees planted: ≈ – trees/year

Cumulative savings vs system cost

Cumulative savings
System cost
Payback point

Find installers for this size Get a free quotation

* Results are a rough estimate from averages (Thai grid CO₂ factor 0.4999 kgCO₂/kWh · panel area 2.58 m²/panel) and are not a quotation. Actual results depend on roof orientation and tilt, shading, usage patterns, tariffs and the equipment chosen. Please ask a partner for an on-site survey before deciding.