How to work out solar system size from your bill
The simplest reliable method starts with the units you actually use, not with a guess about your appliances.
- Find your average monthly units from the 12-month history on your electricity bill.
- Turn it into daily units: divide by 30. For 500 units a month, that is about 16.7 units a day.
- Divide by how much 1 kW of panels produces per day in your area. In much of Pakistan, 1 kW of well-installed panels produces around 4 units a day on average across the year, with more in summer and less in winter and smog.
- Result: 16.7 ÷ 4 ≈ 4.2 kW. Round up to a practical size, such as 4.5 or 5 kW.
You can check the solar potential of your exact location on the Global Solar Atlas, a free World Bank tool. It shows the yearly output per installed kW, which you can divide by 365 and enter in the “units per kW per day” box.
Common system sizes and what they cover
| System | Approx. units per month | Panels (585 W) | Suits |
|---|
Figures assume 4 units per kW per day. Real output in your area may be higher or lower.
On-grid, hybrid or off-grid?
| Type | Batteries | Works in load shedding | Best for |
|---|---|---|---|
| On-grid | No | No (shuts off for safety) | Lowest cost, cities with few outages |
| Hybrid | Yes | Yes | Load shedding plus grid connection |
| Off-grid | Yes, larger | Yes, fully independent | No or very weak grid connection |
Choosing the inverter
The inverter must handle the appliances that run at the same time, not the total of everything you own. Add the wattage of what usually runs together, for example two inverter ACs, fans, lights and the fridge, and leave some margin for motor start-up. The calculator suggests an inverter at least as large as the bigger of your peak load and your panel size, rounded to common sizes.
How much battery do you need?
Battery size depends on what you want to run when the sun is down or the grid is off. Add up the units your essential loads use through the night or a typical outage. Then divide by the usable share of the battery: about 90% for lithium, and about 50% for lead-acid if you want it to last. For 5 units of night backup, that is about 5.6 kWh of lithium or 10 kWh of lead-acid.
Net metering, net billing and payback
In February 2026, NEPRA notified new rules that move new rooftop solar consumers from one-to-one net metering to net billing. Under net billing, units you export are credited at a set buyback rate, which is much lower than the rate you pay for grid units. Reports at the time put the expected new buyback rate at around Rs 11 per unit, and noted that existing net metering users stay on their current terms until their agreements expire. System size is limited to your sanctioned load.
What this means for payback: solar now pays back fastest when you use most of the power yourself, during the day, rather than exporting it. Running ACs, water pumps, washing and ironing in daylight makes a bigger difference than adding extra panels to export. The calculator assumes a share of on-grid output is exported, and values those units at the export rate you enter.
Want to know your current bill before and after solar? Use our electricity bill calculator to see how fewer grid units change your slab and protected status.
Common mistakes when buying solar
- Sizing from one summer bill. It leads to an oversized system that exports cheaply for most of the year.
- Ignoring shade. A water tank or neighbouring wall shading part of the array can cut output more than you expect.
- Choosing an inverter too small for AC and motor start-up loads.
- Skipping earthing and proper DC protection. Safety parts are not where to save money.
- Not cleaning panels. Dust is a real loss in Pakistan; regular cleaning keeps output up.
Frequently asked questions
How many units does a 5 kW solar system produce in Pakistan?
At around 4 units per kW per day, a 5 kW system produces about 20 units a day, or roughly 600 units a month on average. Summer output is higher and winter output lower.
How many panels are needed for a 10 kW system?
With 585 W panels, about 18 panels (10,000 ÷ 585 = 17.1, rounded up). Larger panels mean fewer are needed.
Can a 5 kW system run an AC?
Usually yes, a 1.5-ton inverter AC during the day, alongside normal household load, if the inverter is sized for your peak load. At night it depends on battery capacity.
Is net metering still available in Pakistan?
Under the NEPRA rules notified in February 2026, new consumers move to net billing, where exported units are credited at a lower buyback rate. Existing net metering users keep their current terms until their agreements end.
Why doesn't the calculator show solar prices?
Prices change often and vary by brand and city. Enter quotes from your installer to see payback based on real prices instead of guesses.