Home, energy & building
Solar System Size Calculator
Find the right solar system size for your home or shop. Enter the monthly units from your electricity bill and the panel size, and see how many kW and panels you need, the inverter size, roof space and the bill you could save.
How to use the Solar System Size Calculator
- Enter the monthly units (kWh) from your electricity bill.
- Choose sun hours for your area.
- Enter the panel wattage you plan to buy.
- Choose what share of your units to cover.
- Optionally enter cost per watt to see payback.
Formula
Example
500 units a month in Punjab (5 sun hours) needs about 4.2 kW. With 585 W panels that is 8 panels (4.7 kW), producing about 560 units a month.
On-grid, hybrid or off-grid
- On-grid: cheapest, cuts the bill, no backup during load-shedding
- Hybrid: panels plus batteries, cuts the bill and gives backup
- Off-grid: batteries only, for places with no grid connection
Before you buy
Check the roof for shade, ask for Tier-1 panels and a branded inverter, get the warranty in writing, and make sure the installer handles earthing and DC protection properly.
Read the guide
Related free tools
Frequently asked questions
Which months should I use?
Use the average of summer months if you want AC load covered, or the yearly average for a balanced system.
Do I need batteries?
An on-grid system works without batteries but switches off during load-shedding. A hybrid system with batteries keeps running during power cuts.
What is net metering?
Net metering lets you sell extra units to your DISCO. Its rules and buy-back rates are set by NEPRA and have been revised, so check the latest before you invest.
Results are estimates for planning. For tax, legal or religious decisions, confirm with a qualified person. Your inputs stay in your browser and are not sent to Soft2Cloud.