How Many Solar Panels A 5 Marla House In Pakistan Actually Needs

Three Quotes For One Roof

The third installer was still measuring my roof with a tape when I asked him the question I had asked the other two: how did you land on this size? He said a 5 marla house takes 10 kW, the way a tailor might say a medium shirt takes a medium man.

The first installer, working out of a two-room office near the solar market, had quoted 3 kW and called it enough for a family. The second, who arrived with a printed company folder and a tablet, quoted 5 kW and a very confident delivery date. Same house. Same roof. Same appliances sitting under it. Three sizes, 3, 5 and 10 kW, and a price spread wide enough to buy a motorcycle in the gap.

Nobody in that chain was inventing numbers out of malice. Each quote was a guess wearing a uniform: one sized to the roof, one to the budget he assumed I had, one to the air conditioners he counted on his way in. What none of the three asked about, not once, was how many units the house actually uses in a day. That number lives in exactly one place, the electricity meter on the boundary wall, and I had never read it with any purpose. So before signing anything, I spent one week reading it.

Step One: One Week Of Meter Readings

The method is dull and it works. Read the meter at the same hour every day for seven days, write down the cumulative units, and subtract yesterday from today. My seven days looked like this:

The week totals 191.3 units, which averages 27.3 units a day. Two things stand out in that little table. The days cluster tightly, between about 26 and 29 units, because a house's habits are steadier than its owners believe.

And the average is a number I could defend in any argument with any installer, because it came off my own meter on my own wall. I have written the reading routine up in full, including the fault it once caught at my house, in my guide to Reading Your Electricity Meter To Find Your Real Daily Units. For solar sizing, one honest week is enough to start.

Step Two: Turn Units Into Kilowatts

The bridge between daily units and system size is one planning figure, and I want its assumptions stated as plainly as the number. In Pakistan, one kW of rooftop panels is commonly planned at about 4.2 units of generation per day, averaged across the year, after inverter and wiring losses.

That is the figure the home load calculator uses, and it is deliberately conservative: a clear summer day in Multan beats it comfortably, a cloudy December week falls short of it, and a shaded or badly angled roof falls short of it in every month. Treat 4.2 as the planning average your money is calculated on, not as a promise any single day makes.

The swing behind that average is worth seeing once. On a clear June day the same panels can return 5 or more units per kW, because the sun is high, the day is long and the heat has not yet built the haze that August brings. In a foggy December week the return can sit nearer 3 units per kW, with short days and a low sun doing the damage.

Neither figure is the lie; both are the weather being honest on different dates. A system sized on the June number starves in winter, and a system sized on the December number exports half its summer away at the low credit rate. The planning figure exists to keep the money maths anchored to the year instead of to whichever month the installer visited in.

Now the quotes can be translated into the only language that matters, units per day. A 3 kW system generates about 12.6 units a day. A 5 kW system, about 21. A 10 kW system, about 42. Set those against the house's measured 27.3, and the three confident quotes resolve into what they always were: one system covering less than half the house, one covering about three quarters of it, and one generating half again as much as the house uses, with the surplus exported at a credit rate below the price of a consumed unit.

The measured need is 27.3 divided by 4.2, which is 6.5 kW of generation. The calculator rounds that load up to the 8 kW band, because 8 kW is the standard size on the shelf and the band leaves headroom for the load growth every house manages over a few years.

Three quotes, three sizes, one house. Only one document was missing, and it was a list of the house's own appliances.

Step Three: Count Panels, Not Kilowatts

Kilowatts are what quotes are written in. Panels are what actually arrive on a truck, and the two counts are worth doing separately, because panel wattage is where quiet substitutions happen. Modern residential panels in this market are commonly 550 W or 580 W apiece. The panel count for any target is the target in watts divided by the panel rating, rounded up:

I signed for 14 panels of 580 W on an 8 kW inverter: 8,120 W of panels over a measured need of 6.5 kW, with the headroom earmarked for load growth rather than export. If your week of readings lands lower, your panel count should land lower with it.

A house using 15 units a day needs 3.6 kW of generation, which is 7 panels of 550 W, and no installer should be able to talk that house into 16 panels by pointing at the roof. The roof is not the load. The meter is the load, and the meter had already given its answer before any installer climbed the stairs.

Before You Sign Anything

Three checks protected the money once the size was settled. First, certification: net metering applications in Pakistan run through installers certified under the AEDB regulations, and the official certified installer list is published by PPIB, so a company's name either appears on it or the conversation ends.

Second, serial numbers: get every panel's serial number written on the invoice, because warranty claims and quiet panel swaps both turn on that list. Third, the load sheet stays attached to the contract, so the agreed size stays tied to the measured number rather than to a sales conversation nobody can reconstruct later.

I went through the paperwork side of three real quote structures line by line in a companion piece, including which line items hide the padding and which fees are genuine, in my checklist for Checking A Solar Installer's Quote Against Your Own Load Sheet. Read it after this one if a quote is already sitting on your table. The order matters: measure first, size second, sign last. My three quotes are still in a drawer, and the 10 kW one, for a house that uses 27.3 units a day, is the best argument I own for that order.