How units become kilowatts
A “unit” on your bill is one kilowatt-hour. The calculator works backwards from the units you use each month to the panels that will produce the same energy:
- Units per day = monthly units ÷ 30.
- Array kW = units per day ÷ (peak sun hours × system efficiency of 82.6%).
- Panels = array watts ÷ panel watts, rounded up.
- Inverter kW = array kW ÷ 1.2 (typical DC/AC ratio), rounded up to the next 0.5 kW.
Monthly units and the solar system they need
At the national planning average of 5.3 peak sun hours, with 550 W panels. Open a row for city-by-city numbers.
| Monthly units | Array needed | 550 W panels | Guide |
|---|---|---|---|
| 200 units | 1.5 kW | 3 | Solar for 200 units → |
| 300 units | 2.3 kW | 5 | Solar for 300 units → |
| 400 units | 3 kW | 6 | Solar for 400 units → |
| 500 units | 3.8 kW | 7 | Solar for 500 units → |
| 600 units | 4.6 kW | 9 | Solar for 600 units → |
| 700 units | 5.3 kW | 10 | Solar for 700 units → |
| 800 units | 6.1 kW | 12 | Solar for 800 units → |
| 1,000 units | 7.6 kW | 14 | Solar for 1000 units → |
| 1,200 units | 9.1 kW | 17 | Solar for 1200 units → |
| 1,500 units | 11.4 kW | 21 | Solar for 1500 units → |
| 2,000 units | 15.2 kW | 28 | Solar for 2000 units → |
How many units does a solar system produce?
| System size | Units per day | Units per month | Guide |
|---|---|---|---|
| 1 kW | 4.4 | 131 | — |
| 2 kW | 8.8 | 263 | — |
| 3 kW | 13.1 | 394 | 3 kW guide → |
| 5 kW | 21.9 | 656 | 5 kW guide → |
| 7.5 kW | 32.8 | 985 | — |
| 10 kW | 43.8 | 1,313 | 10 kW guide → |
| 15 kW | 65.6 | 1,969 | 15 kW guide → |
| 20 kW | 87.5 | 2,625 | 20 kW guide → |
Planning averages at 5.3 peak sun hours. Summer months produce more and winter months less.
Net metering vs net billing in Pakistan
In February 2026 NEPRA replaced net metering with a net-billing model for new solar consumers. Under net billing, units you export are credited at a lower buyback rate than the price you pay for imported units, so using more of your own solar output directly (daytime loads, or a battery) is worth more than exporting it. Reports put agreements signed before 9 February 2026 outside the new rules, and sources differ on the exact new rate. Read the report.
Rules and rates have been revised more than once, so confirm the current buyback rate and eligibility with NEPRA or your distribution company before you decide on system size or a battery.
Frequently asked questions
How do I convert my electricity units to a solar system size?
Divide your monthly units by 30 to get units per day, then divide by the peak sun hours and the system efficiency. At 5.3 peak sun hours and 82.6% efficiency, 500 units a month needs about 3.8 kW of panels.
How many units does a 5 kW solar system produce per month?
At 5.3 peak sun hours a 5 kW array produces about 656 units a month on average, more in summer and less in winter.
How many solar panels do I need for 500 units?
About 7 panels of 550 W at 5.3 peak sun hours. The wizard above recalculates for your city and panel size.
Do I need a battery?
Only if you want backup during outages or to use solar at night. An on-grid system without a battery is the cheapest option but stops working when the grid is down, because standard grid-tie inverters shut off for safety.
Why does the answer depend on the city?
Cities receive different amounts of sunshine. More sun hours mean fewer panels for the same units. The calculator pre-fills a planning value for each city and lets you change it.
Is the result a quotation?
No. It is a planning estimate. Get a site survey and written quotation from a qualified installer, who will check roof space, shading, wiring and inverter compatibility.