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 September 2026 market prices 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.
How the solar load calculation works
1. Units a day
Take your average monthly units from the 12-month history on your bill and divide by 30.4. For a load list, add up watts x hours for each appliance and divide by 1,000.
2. Panel size
Divide the daily units 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. Round up to whole panels.
3. Inverter
The inverter must carry your largest load running at once, with 25% spare for motors and compressors starting up. It can be somewhat smaller than the panels, because panels rarely give their full rating in Pakistani heat: we allow panels up to 1.3 times the inverter size.
4. Batteries
Battery kWh = backup load in kW x hours ÷ usable depth of discharge ÷ inverter efficiency. Lithium (LiFePO4) batteries can use about 90% of their capacity. Tubular lead-acid batteries should not go much below half, so they need nearly twice the capacity for the same backup.
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 September 2026 prices below, this system with its battery costs roughly Rs 564,000 to Rs 764,000. 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 17,260 a month, a payback of about 2.7 to 3.7 years.
How to calculate battery backup time
Backup hours = battery kWh x usable share x inverter efficiency x 1,000 ÷ load in watts
Battery kWh is volts x amp-hours ÷ 1,000. A 12 V 200 Ah tubular battery holds 2.4 kWh. Using half of it through a 90% efficient inverter gives 2.4 x 0.5 x 0.9 = 1.08 kWh, which runs a 300 W load of fans and lights for about 3.6 hours. A 51.2 V 100 Ah lithium pack holds 5.12 kWh; at 90% usable and 90% efficiency it runs the same 300 W for about 13.8 hours.
Batteries lose capacity with age and in heat, so a two or three year old tubular battery gives noticeably less backup than when new.
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, reported at 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, September 2026
Dealer price lists in September 2026 showed panels at about Rs 35 to 47 per watt depending on brand, 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. 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. We have not included tubular battery prices.
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.
What size inverter do I need for a 1.5 ton inverter AC?
A 1.5 ton inverter AC can draw up to about 1.8 kW at full speed. Add fans, lights and a fridge, say 0.6 kW, then 25% spare for starting loads: 2.4 x 1.25 = 3 kW. So 3 kW is the minimum for one such AC, and two ACs need about 5 to 6 kW. Enter your own appliances in the calculator to check.
How long will a 200 Ah battery run a fan?
A 12 V 200 Ah tubular battery holds 2.4 kWh. Using half of it through a 90% efficient inverter gives about 1.08 kWh. An 80 W fan would run about 13.5 hours, and two fans with four LED bulbs, about 208 W, would run roughly 5 hours. A lithium battery of the same size gives nearly twice the backup.
Is net metering still available in Pakistan?
Not for new applicants. Since 9 February 2026 new users get net billing under the NEPRA (Prosumer) Regulations 2026, with exports credited at the national average energy purchase price. Users with agreements signed before that date keep their old net metering terms until their agreement ends.
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 29 September 2026. Results are estimates; official notices always take precedence.