What size solar system do you need? Work it out from your bill

To find what size solar system you need, add up the units on your last 12 electricity bills and divide by what 1 kW of panels makes in a year in your city: about 1,466 units in Lahore and 1,697 in Karachi, from World Bank Global Solar Atlas data. A Lahore home using 500 units a month (6,000 a year) needs about 4.1 kW. Then check that size against your sanctioned load, because net billing won’t connect a bigger system.

How many units does 1 kW of solar produce per day in Pakistan?

We took the long-term figures for each city from the Global Solar Atlas, the World Bank and ESMAP’s solar data tool built on Solargis data (data period up to 2025, updated April 2026). The “per day” and “per month” columns are our arithmetic from the yearly figure.

So a 5 kW system makes about 20 units a day in Lahore and 23 in Karachi, and a 10 kW system about 40 units a day in Lahore (around 1,220 a month) and 46.5 in Karachi, averaged over the year.

What size solar system do I need for my bill?

Divide your yearly units by your city’s yearly figure above. If you only have one bill, multiply the units by 12 first, but a full year is better, because summer and winter bills differ a lot.

This table covers your units over a whole year. It doesn’t mean every month’s bill goes to zero: in winter the same panels make less.

How many solar panels do I need to power my house?

A household in Lahore adds up 12 bills and gets 6,000 units a year.

That’s about 496 units in an average month. But January would give about 378 units and April about 595, so expect a small bill in winter and spare units in spring.

The 580 W panel and its size come from a JinkoSolar Tiger Neo datasheet. Prices for panels like this are in our solar panel price guide, and full-system costs are in what a solar system costs.

Does my sanctioned load limit the system size?

Yes, if you want to sell units back to the grid. NEPRA’s Prosumer Regulations, notified on 9 Feb 2026, replaced net metering with net billing for new users.

Dawn and Profit report that a new system can’t be bigger than your connection’s sanctioned load, down from 1.5 times before. So a home with a 5 kW sanctioned load can connect our 4.06 kW example, but not a 7 kW system.

Two more points from the same reports:

• New prosumers get about Rs 10 to Rs 11 per exported unit, while a three-phase home using over 600 units pays about Rs 47 per unit it imports. A unit you use yourself is worth far more than a unit you export, so oversizing pays back less than it used to.
• DISCOs stop accepting applications on a transformer once solar connected to it reaches 80% of its rated capacity.

We couldn’t open NEPRA’s website to read the regulations themselves (it blocked our requests), so these rules come from news reports. See our net metering guide for the rules and how to apply for net billing for the steps.

How much roof space does a solar system need?

The JinkoSolar 580 W panel measures 2,335 × 1,134 mm, or about 2.65 square metres. By our arithmetic that’s about 4.6 square metres (49 sq ft) of panel per kW, and the 7-panel example covers about 18.5 square metres (200 sq ft). Leave extra room for walkways, frames and gaps between rows, and keep panels out of the shade of water tanks and walls.

Can a solar system run a 1 ton AC, and how many ACs can 10kW run?

Haier Pakistan lists one of its 1-ton DC inverter ACs at 0.36 to 1.39 kW of power input while cooling. Over 8 hours, that is between 2.9 and 11.1 units, depending on how hard the AC has to work.

• One 1-ton inverter AC in the day: at the top of that range, 11.1 units is what about 2.8 kW of panels make on an average Lahore day.
• 10 kW system: about 40 units a day in Lahore covers the energy for about 3 such ACs running flat out for 8 hours, or many more running at low power.

For fans, ARY News reports that conventional ceiling fans use 70 to 90 watts and inverter fans are sold as using about 30 watts at low or medium speed (40 to 50 watts at full speed). Five conventional fans at 80 W for 12 hours use 4.8 units a day; five inverter fans at 30 W, 1.8 units.

How big a battery do I need for backup?

Batteries are sized for the hours you want to cover, not for your whole bill.

Battery size (kWh) = load (kW) × hours of backup ÷ usable share of the battery

The usable share is the depth of discharge on the battery’s datasheet. Max Power, a battery seller, says lithium batteries can go to 90% to 95% and tubular lead-acid batteries only to 50%.

• Four conventional fans for 6 hours: 4 × 80 W × 6 h = 1.92 kWh; ÷ 0.9 = about 2.1 kWh of lithium battery.
• Add one 1-ton inverter AC for 6 hours: another 2.2 to 8.3 kWh before dividing by the usable share.

Prices are in our lithium battery price guide.

More guides: Solar costs and payback, net metering, solar system prices, solar calculator, solar loans and instalment plans.