About solar panel calculator
To size a solar system, start from how much electricity you use and how much sun your roof gets.
Method
System size (kW) = monthly units ÷ (30 × daily generation per kW). For 450 units a month and 4.5 units per kW per day, you need about 3.3 kW.
Panels and roof area
- A modern 540 W panel is roughly 2.3 m² (about 25 ft²).
- A 3 kW system needs around 6 panels and roughly 20 m² of shade-free roof.
- Face panels south in India, with a tilt close to your latitude.
Get a site survey
Shading, roof strength and wiring decide the final design. Ask installers for a survey and compare quotes.
A worked example
A home using 450 units a month needs about 450 ÷ (30 × 4.5) = 3.3 kW, so a 3.5 kW system is a sensible size. With 540 W panels that is 7 panels, which take up around 16 square metres of shade-free roof.
Also consider
- Net metering rules in your state, which decide how surplus power is credited.
- Whether you want batteries for backup, which add cost.
- Future needs, such as an air conditioner or an electric vehicle.
