How Much Roof Do You Need for a 10 kW Solar System?

This is the question people ask before they ask about price, and rightly so. If the roof cannot take the array, everything else is academic. Here is the arithmetic, and then the part the arithmetic leaves out.

The arithmetic

Panel wattages have climbed steadily. A module around 585 W measures roughly 2278 by 1134 mm, which is about 26 square feet of glass. Higher wattage panels mean fewer panels for the same capacity, which is genuinely useful on a constrained roof — one of several reasons the panel selection and the roof survey are the same conversation.

Why usable roof is smaller than your roof

Walk onto most roofs in Lahore and measure honestly, and the number drops fast:

• Water tanks — and more importantly the shadow they throw, which moves across the day
• The stairwell block, which is usually in exactly the wrong place
• Parapet walls, whose shadows run long in winter when the sun is low
• Air conditioner outdoor units and their service clearance
• Row spacing — tilted rows must be far enough apart not to shade the row behind
• Walkways — you need to reach the array to clean it, and cleaning matters more here than most places, as we set out in why solar output drops in Pakistan

That last point is worth dwelling on. An array packed edge to edge with no walkway is an array that will not be cleaned properly, and in this climate that quietly costs you a serious share of your generation every year.

Rough sizes for other systems

Treat these as planning figures for a first conversation, not as a design. Marla varies by region and the panel count moves with wattage, so the survey is what turns these into a number you can rely on.

Does roof direction matter?

Yes, and the answer has become more interesting under net billing. A south-facing array generally produces the most across the year in Pakistan. But east or west facing arrays spread generation into the morning or the afternoon rather than concentrating it at midday.

Under the old net metering rules that was simply worse. Now that exported units earn a fraction of what imported ones cost, an array that lines generation up with when you actually consume can beat a south-facing one that produces more in total but exports the surplus cheaply. We explained why in net metering to net billing.

A west-facing array on a house that runs air conditioning until 6pm can be the right answer. Nobody would have recommended that three years ago.

What if the roof is not big enough?

1. Size the system to the roof. A 7 kW system that fits properly beats a 10 kW system crammed in with no walkways and self-shading rows.
2. Use higher wattage panels. Fewer modules for the same capacity, which buys back area.
3. Use other structures. A car porch, a shed roof or a boundary structure — we manufacture the mounting systems for all three, covered in choosing a mounting structure.
4. Ground mount, if you have land. Easier to clean, easier to tilt properly, and no roof loading question.

What we will not do is tell you that 10 kW fits on a roof where it does not. An array squeezed in without spacing shades itself, cannot be cleaned, and underperforms for twenty-five years to satisfy a number on a quotation.

Roof space: questions people actually ask

The bottom line

Plan on 550 to 700 square feet of clear roof for 10 kW, measure the usable area rather than the total area, and leave room to walk between the rows. Then let the roof decide the system size rather than the other way round.