Step 1: find your daily energy use
Take your monthly units (kWh) from your electricity bill and divide by 30. For example, 300 units a month is about 10 kWh per day.
Step 2: estimate sun hours
Peak sun hours depend on the season and your location. A figure of about 4 to 6 hours is common in Pakistan, and 5 hours is a reasonable planning number.
Step 3: calculate system size
System size (kW) = daily kWh ÷ (sun hours × 0.8). The 0.8 allows for real-world losses.
Step 4: check roof space
A typical 550 W panel measures roughly 2.3 m × 1.1 m, so about 2.5 m² each. Allow room for walkways and avoid shade from tanks, walls or trees, especially between mid-morning and mid-afternoon.
Step 5: match the inverter
Choose an inverter rated for your loads and with a PV input that fits your panel array. If you want battery backup, you need extra panel capacity to charge the batteries as well as run your loads. Read the inverter type guide for help.
Tips that improve results
- Compare price per watt, not just price per panel.
- Modern monocrystalline panels are more efficient than older polycrystalline panels and give more power in the same space.
- Angle the panels close to your latitude and face them towards the south for the best yearly output.
- Keep panels clean; dust reduces output.
Buy panels or get a site visit
See our solar panels, or let us do the sizing for you. We also offer solar installation across Pakistan.