To size a solar system, divide the units you use per day by the units 1 kW of panels makes per day in your city. A Lahore home using 400 units a month needs 13.15 units a day. Lahore gets about 5.08 peak sun hours, and after 22% losses 1 kW of panels makes about 3.96 units a day, so the home needs about 3.3 kW, which is 6 panels of 585 W.
The calculator does this for 11 cities, then sizes the inverter, the battery bank for the backup you want, the roof space, a cost range at the dealer prices stored in the calculator (September 2026) and the payback time. Switch to "From appliances" to build the load from fans, ACs and other appliances instead.
Peak sun hours in Pakistan by city
Peak sun hours are the day's sunlight on panels at the best fixed tilt, counted as hours of full sun (1,000 W per sq m). Figures are long-term averages from the Global Solar Atlas, published by the World Bank. Units per kW assume 22% losses.
| City | Peak sun hours | Units a day per kW | Units a month per kW | Lowest month | Best tilt |
|---|---|---|---|---|---|
| Lahore | 5.08 | 3.96 | 121 | 92 (Jan) | 28° |
| Karachi | 5.94 | 4.63 | 141 | 106 (Aug) | 27° |
| Islamabad and Rawalpindi | 5.38 | 4.20 | 128 | 101 (Jan) | 30° |
| Peshawar | 5.21 | 4.06 | 124 | 98 (Jan) | 30° |
| Quetta | 6.78 | 5.28 | 161 | 140 (Feb) | 32° |
| Multan | 5.65 | 4.41 | 134 | 104 (Jan) | 28° |
| Faisalabad | 5.22 | 4.07 | 124 | 94 (Jan) | 28° |
| Gujranwala | 5.10 | 3.98 | 121 | 90 (Jan) | 28° |
| Bahawalpur | 5.80 | 4.52 | 138 | 110 (Jan) | 28° |
| Hyderabad | 6.21 | 4.85 | 147 | 128 (Jul) | 26° |
| Sukkur | 6.06 | 4.72 | 144 | 126 (Dec) | 27° |
Winter is the weak season in Punjab and Khyber Pakhtunkhwa: a Lahore system makes only about three quarters of its average in January. In Karachi and Hyderabad the monsoon months of July and August are the weakest. If you need solar to cover a winter geyser or heater, size for the lowest month rather than the average.
From monthly units to panels and inverter
Panel size
Take your average monthly units from the 12-month history on your bill and divide by 30.4 to get units a day. Divide that by what 1 kW of panels makes in your city: peak sun hours x (1 minus losses). Losses cover heat, dust, wiring and the inverter. Global Solar Atlas figures imply about 21%, so we use 22% as the default, then round up to whole panels.
Inverter
The inverter must carry the largest load running at once, with 25% spare for motors and compressors starting up. Panels can be up to 1.3 times the inverter size, because they rarely give their full rating in Pakistani heat.
If you do not know your units, list your appliances in the solar load calculator, which works out watts, day and night units and the inverter size from them.
How many solar panels do I need? Quick sizes for Lahore
Panel sizes for common monthly bills in Lahore, with 585 W panels and 22% losses. The inverter column is sized from the panels alone; a home with two ACs may need a bigger one.
| Units a month | Panels needed | Panels (585 W) | Inverter |
|---|---|---|---|
| 200 | 1.66 kW | 3 × 585 W = 1.76 kW | 3 kW |
| 300 | 2.49 kW | 5 × 585 W = 2.93 kW | 3 kW |
| 400 | 3.32 kW | 6 × 585 W = 3.51 kW | 3 kW |
| 500 | 4.15 kW | 8 × 585 W = 4.68 kW | 4 kW |
| 700 | 5.81 kW | 10 × 585 W = 5.85 kW | 5 kW |
| 1,000 | 8.29 kW | 15 × 585 W = 8.78 kW | 8 kW |
Karachi and Quetta need about 15 to 25% fewer panels for the same units, because they get more sun. Use the calculator for your own city.
Worked example: 400 units a month in Lahore
This is the example loaded in the calculator.
- Units a day: 400 ÷ 30.4 = 13.15
- 1 kW makes: 5.08 peak sun hours x 78% = 3.96 units a day
- Panels needed: 13.15 ÷ 3.96 = 3.32 kW, so 6 panels of 585 W = 3.51 kW, about 168 sq ft of roof
- Inverter: a peak load of 3,000 W x 1.25 = 3.75 kW, so a 4 kW inverter
- Output: about 423 units in an average month, 323 in January and 508 in April
- Battery for 800 W over 4 hours: 3.2 kWh ÷ 0.9 ÷ 0.9 = 3.95 kWh, so one 51.2 V 100 Ah lithium pack of 5.12 kWh, which runs 800 W for about 5.2 hours
At the dealer prices below, this system with its battery costs roughly Rs 563,850 to Rs 763,500. If the home uses 70% of the solar units itself at Rs 54 a unit and exports the rest at Rs 10, it saves about Rs 17,265 a month, a payback of about 2.7 to 3.7 years.
Batteries in a solar system
The calculator sizes the battery bank from the backup load and hours you enter. Lithium (LiFePO4) packs can use about 90% of their capacity, while tubular batteries should not go much below half, so they need nearly twice the capacity for the same backup. For backup time from a battery you already own, use the UPS battery backup calculator.
Net metering and net billing in 2026
The rules for selling solar power to the grid changed in 2026.
- March 2025: the Economic Coordination Committee approved cutting the buyback rate for new net metering users from about Rs 27 to Rs 10 a unit. The federal cabinet did not ratify it and asked for wider consultation.
- 9 February 2026: NEPRA notified the NEPRA (Prosumer) Regulations 2026, replacing the 2015 net metering regulations. New users move to net billing: units you import are billed at the normal consumer tariff, and units you export are credited at the national average energy purchase price, about Rs 10 to 11 a unit when the rules were notified. The agreement term is 5 years instead of 7, and the system may not be bigger than your sanctioned load.
- April 2026: after the Prime Minister asked for existing users to be protected, NEPRA amended the regulations. Users whose agreements were signed before 9 February 2026 stay on the old net metering rate and method until their agreement expires, unless they materially change the system. Applications filed by 8 February were to be processed under the old rules.
Under net metering, an exported unit cancelled an imported unit. Under net billing, an exported unit is worth only a fraction of an imported one. So a new system pays back fastest when you use its units yourself during the day. That is why the calculator asks what share of solar you use yourself. Set the export rate to the figure on your own agreement.
Solar system cost in Pakistan
Dealer price lists of September 2026 showed complete on-grid systems at about Rs 95,000 to Rs 130,000 per kW installed, and lithium batteries at about Rs 45,000 to Rs 60,000 per kWh. Panels alone were about Rs 35 to 47 per watt depending on brand. The calculator uses these ranges. Prices follow the dollar and change often, so treat the result as a guide and compare two or three written quotes. Tubular battery prices are not included.
This is a sizing guide, not a design. An installer should check your roof, shading, wiring and your electricity company's approval requirements. Sunlight figures are long-term averages, so a cloudy month can be well below them. Sanctioned load limits and net billing terms come from your company and NEPRA, not from us.
Solar questions
How many solar panels do I need for 300 units a month?
In Lahore, about 2.5 kW, which is 5 panels of 585 W. Divide 300 units by 30.4 days to get 9.9 units a day, then divide by the 3.96 units a day that 1 kW makes in Lahore after losses. In Karachi, 1 kW makes about 4.63 units a day, so slightly fewer panels do the same job.
How much roof space do solar panels need?
A 585 W panel is about 2.28 m by 1.13 m, roughly 28 sq ft. The Lahore home using 400 units a month needs 6 panels, about 168 sq ft of roof. Leave extra space for walkways and gaps between rows so the panels do not shade each other.
Does net billing change how big my system should be?
Yes. New connections since 9 February 2026 are on net billing, where exported units earn far less than imported units cost, so size the panels for the units you use yourself in daylight rather than for exporting. The solar net metering calculator compares net billing with the old net metering for your own readings.
Should I choose lithium or tubular batteries?
Lithium costs more at the start but lets you use about 90% of its capacity, lasts many more cycles and needs no water. Tubular batteries are cheaper but should only be run down to about half, so you need about twice the capacity, and they wear out sooner in daily solar use. For daily cycling, lithium usually costs less over its life.
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Last reviewed 9 October 2026. Results are estimates; official notices always take precedence.