Sizing solar for summer AC load in Lahore

Why summer AC load is the design driver in Lahore

For most Lahore households the single biggest electricity load of the year is the summer air-conditioning bill. June, July and August consumption can be three to four times the December consumption on the same house. A solar system that does not handle the summer load is a system that under-delivers on its main job.

The problem is that buyers often size the system based on the average bill across the year, not the summer peak. A household averaging 600 kWh per month gets quoted a 5 kW system. That system works fine in October and February. In June, when consumption rises to 1,400 to 1,800 kWh, the system covers maybe 65 percent of the load. The household ends up with a still-large LESCO bill in the months where the bill matters most.

Right-sizing for Lahore means sizing for the summer peak.

What an inverter AC actually pulls

The nameplate ton rating of an AC is misleading for solar sizing. Buyers see "1.5 ton inverter AC" and assume 1.5 kW. The reality is more nuanced.

A 1.5-ton inverter AC has a peak compressor draw of roughly 1,500 to 1,800 watts when ramping up. After it reaches the set temperature, it cycles down to a steady-state draw of 600 to 1,100 watts depending on outdoor temperature, indoor heat load, set point, and how recently the door or window was opened. On a Lahore June afternoon with the outdoor temperature at 44 degrees Celsius, the steady-state draw of a 1.5-ton inverter AC averages 1,100 to 1,400 watts.

A 1-ton inverter AC averages 750 to 1,000 watts in the same conditions. A 2-ton inverter AC averages 1,500 to 1,900 watts.

A non-inverter (conventional) AC of the same ton rating draws 30 to 45 percent more on average because it cycles between full power and off rather than modulating.

Run hours that matter in Lahore

For a typical 10-marla Lahore home in June with three inverter ACs, the realistic running pattern looks like this.

The bedroom ACs run from about 10 pm to 7 am, which is 9 hours. That is mostly outside solar generation hours, so the load is either grid or battery.

The living room AC runs from about 2 pm to 11 pm, which is 9 hours. The first 4 to 5 hours overlap with strong solar generation. The last 4 to 5 hours run on grid or battery.

A second living-area or study AC runs from about 4 pm to 11 pm, which is 7 hours. The first 2 to 3 hours overlap with solar.

Total daily AC load: 9 plus 9 plus 7 equals 25 AC-hours. At an average of 1.2 kW per inverter AC steady-state, that is 30 kWh of AC consumption alone, before the fridge, fans, lights, TV, water motor and other loads.

Why 5 kW is not enough for three ACs

A 5 kW solar system in Lahore produces 27 to 30 kWh on a sunny June day. That is enough to cover the daytime AC load if there is only one AC running during sunlight hours and the household self-consumes everything. It is not enough to cover three ACs plus the rest of the household.

The total daily household load for a three-AC Lahore home in June is typically 55 to 70 kWh. Solar generation of 27 to 30 kWh covers about 40 to 45 percent of that load. The remaining 60 percent comes from the grid.

The buyer who installed a 5 kW system expecting summer bill elimination sees a June bill of PKR 28,000 to PKR 40,000 instead of PKR 70,000 to PKR 90,000. The savings are real, but the expectation was wrong. The system did not fail. The sizing was off.

The right-size table for Lahore summer AC homes

Household setup	Summer kWh / month	Right system size	Inverter
1 inverter AC, 7-marla	500 – 700	5 kW solar	5 kW hybrid
2 inverter ACs, 7-marla	800 – 1,100	7 kW solar	8 kW hybrid
2 inverter + 1 non-inverter, 10-marla	1,100 – 1,400	10 kW solar	10 kW hybrid
3 inverter ACs, 10-marla	1,400 – 1,800	12 kW solar	12 kW hybrid
4 ACs, 1-kanal	1,800 – 2,400	15 kW solar	15 kW hybrid
5+ ACs, 1-kanal	2,400 – 3,200	20 kW solar	2 x 10 kW or 20 kW

These numbers assume a hybrid inverter, net metering or net billing active, and the goal of covering 85 to 95 percent of the summer monthly consumption through a combination of self-consumption and grid export credits.

Inverter sizing — not just panel sizing

The inverter is the gate between the panels and the household. If the inverter is undersized, the panels can produce more than the inverter can convert, and the excess is wasted. If the inverter is oversized relative to the panels, the buyer paid for unused capacity.

The right approach for Lahore summer load is to size the inverter to handle the peak running load of the household, including all ACs running simultaneously. For a three-inverter-AC home with an additional 2 kW of other loads, peak simultaneous draw is around 5 to 6 kW. A 10 kW hybrid inverter handles this comfortably with headroom for surge during AC compressor start-up.

Match the panel-to-inverter ratio in the 1.1 to 1.3 range. A 10 kW inverter pairs well with 11 to 13 kW of panels. On a Lahore summer day the inverter rarely sees full 10 kW input from the panels (because temperature, dust, and angle all knock down peak output), so a slightly oversized panel array squeezes more energy out of the same inverter.

The battery question for AC-heavy homes

The bedroom ACs run mostly at night. The panels are not generating then. Without a battery, the bedroom AC load is 100 percent on the grid.

A 15 kWh lithium battery, on a 10 kW solar system, can cover 8 to 10 hours of bedroom AC for two ACs. The battery charges from the panels during the day after the household's daytime load is met. This shifts the bedroom AC load off the grid entirely on most summer days.

The financial maths depends on the bill slab. For a household whose grid consumption was at the PKR 41 or PKR 56 slab before solar, every kWh shifted off the grid via battery saves PKR 41 to PKR 56. The same kWh exported via net billing earns PKR 27. The battery effectively converts a PKR 27 export into a PKR 41 to PKR 56 saving, a delta of PKR 14 to PKR 29 per kWh.

A 15 kWh battery doing one full cycle a day at this delta produces savings of roughly PKR 210 to PKR 435 per day in summer, or PKR 6,300 to PKR 13,050 per month. The battery cost of PKR 800,000 to PKR 1,100,000 pays back in 6 to 10 years on the battery savings alone, plus the load-shedding backup value on top.

The honest answer for three-AC Lahore households

The right system for a three-inverter-AC Lahore home is a 12 kW solar array with a 10 to 12 kW hybrid inverter, plus 15 kWh of lithium battery. Turnkey cost in May 2026 lands between PKR 2,400,000 and PKR 3,100,000.

The monthly summer bill on this setup drops from PKR 65,000 to PKR 95,000 down to PKR 4,000 to PKR 12,000. Annual savings are PKR 580,000 to PKR 780,000. Payback period is 3.8 to 4.5 years on a 20-plus year asset.

The shortcut answer of "just buy a 5 kW system because that is what the neighbour bought" produces a system that does only part of the job. Lahore's summer AC load demands proper sizing or the result is a buyer who is half-disappointed.