Solar System Sizing Basics

Last reviewed: October 2026

You can estimate the size of a solar system with a few numbers from your electricity bill and your appliance list. This guide gives a simple method; a site visit is still the best way to confirm the design.

Step 1: Find your daily energy use

Your bill shows units consumed in a month — one unit is one kilowatt-hour (kWh). Divide a typical monthly figure by 30 to get daily kWh. Use a summer month if air conditioners are a large part of your load.

Step 2: Find your load (kW)

Add the running watts of the appliances you want to run at the same time. Use our load calculator. This sets the inverter size.

Step 3: Estimate panel size (kW)

As a rule of thumb, each 1 kW of panels may produce roughly 4–5 kWh per day on a good day in Pakistan after system losses. Real output varies with season, tilt, shade, dust and temperature. So: panel kW ≈ daily kWh ÷ 4 (use a lower divisor to be conservative).

Step 4: Size the inverter

Inverter kW ≥ simultaneous load × 1.25, and check the surge rating for motors and air conditioners. Panel capacity is often sized somewhat above the inverter rating, within the inverter's maximum solar input limit. Details in how to choose a solar inverter.

Step 5: Size the battery (if you need backup)

Battery kWh ≈ the energy you want to run during an outage ÷ usable fraction of the battery. See the lithium battery guide.

Worked example (illustrative only)

• Monthly use 600 units → 20 kWh per day.
• Panels: 20 ÷ 4 = about 5 kW.
• Simultaneous load of 3.5 kW → 3.5 × 1.25 ≈ 4.4 kW → choose the next standard inverter size up.
• Backup of 3 hours at 1.5 kW essential load = 4.5 kWh → a battery with roughly 5 kWh of usable capacity.

These figures are an example to show the method, not a recommendation for your home.

Next steps

Send us your monthly units, your key appliances and your backup requirement through the contact form and we will suggest suitable equipment and confirm pricing and availability.