Sizing is the one decision that is expensive in both directions. Too small and you are still paying PESCO every month for the units your system never covered. Too big and you have spent lakhs on panels whose output you give away.

Almost everything else about a solar system can be adjusted later. Size is the part you commit to on day one, so it is worth twenty minutes of arithmetic before anyone quotes you.

1. Start with your bill, not with a panel count

The only number that matters at the start is units consumed (kWh) on your PESCO bill.

  • Take an average of your summer months, not the whole year. Summer is when your usage peaks, and a system sized to your winter bill will disappoint you in June.
  • Divide the monthly units by 30 to get your daily usage.

If your bill says 600 units in July, you are using about 20 units a day. That single number drives everything that follows.

2. The rule that works in Peshawar

In our conditions, every 1 kW of panels generates roughly 4 units per day, averaged across the year. That figure already accounts for about five peak sun hours and normal system losses — it is a realistic number, not a brochure number.

Working backwards from your bill:

  • 300 units/month (~10 a day) → about 2.5–3 kW
  • 500 units/month (~17 a day) → about 4–5 kW
  • 900 units/month (~30 a day) → about 7–8 kW
  • 1,500 units/month (~50 a day) → about 12–13 kW

Be suspicious of anyone who quotes you a much smaller system for the same bill. The maths above is not controversial, and a system that looks cheap because it is undersized is not a saving.

Air conditioning changes the answer

Each inverter AC adds roughly 1.5–2 kW to your peak load. This matters differently depending on the system you choose:

  • For a daytime or on-grid system, what matters is total units over the month — ACs push your consumption up, so they push your kW up.
  • For a hybrid system, ACs also decide your inverter size, because the inverter has to carry them all at the same instant. Two ACs running together is a very different demand from two ACs running at different times.

If you plan to add air conditioning next summer, size for that now. Adding panels later is easy; replacing an undersized inverter is not.

3. Will it fit on your roof?

A useful planning figure: each 1 kW needs about 60–70 square feet of shade-free roof — roughly two modern panels.

  • 3 kW → about 180–210 sq ft
  • 5 kW → about 300–350 sq ft
  • 10 kW → about 600–700 sq ft

Higher-efficiency panels need less area for the same power, which genuinely matters on a small roof.

Space is rarely the real constraint, though. These four things matter more:

  • Shade. A single shadow — a water tank, a parapet wall, a neighbour's new storey, a pole — can drag down an entire string of panels, not just the one it covers. Shade is the most common reason a system underperforms its quote.
  • Orientation and tilt. South-facing at the right angle produces the most across the year in our region.
  • Structure. Flat roofs need a tilted mounting structure; sloped roofs mount along the slope. In windy areas this is not the place to economise.
  • Room to grow. If you might add panels later, plan the layout now rather than discovering there is nowhere sensible to put them.

4. On-grid, hybrid or off-grid?

This choice confuses more first-time buyers than any other, and getting it wrong is what leaves people either overpaying or sitting in the dark.

On-grid (also called daytime, or grid-tied)

Solar and the grid, no battery. Your surplus daytime units flow back to PESCO through net metering and are credited against what you draw at night.

  • Cheapest option and the best payback.
  • No backup. During load shedding the system shuts down automatically for safety — this is a legal requirement, not a fault.
  • Best for homes and businesses with reasonable grid supply whose main goal is the bill.

Hybrid

Solar, battery and grid together. You get the daytime savings *and* backup during outages.

  • Costs more, because of the battery.
  • You can start without batteries and add them later, provided the inverter is hybrid from the beginning.
  • For most homes in Peshawar this is the right answer, simply because load shedding is a daily fact rather than an occasional event.

Off-grid

No grid connection at all. Needs a larger battery bank and careful sizing, because there is nothing to fall back on.

  • Best for remote areas, farmhouses, and tube wells where the grid is absent or hopeless.
  • Rarely the right answer inside the city.

Deciding in one line

  • Decent grid, and you mainly want a lower bill → on-grid.
  • Load shedding is a daily problem → hybrid.
  • No usable grid at all → off-grid.

There is no single best system, only the best system for your load, your roof and your budget. Anyone who recommends the same setup to every customer is selling stock, not designing.

5. Check the numbers yourself

Two free tools on this site will do the arithmetic for you:

  • The solar calculator estimates cost, monthly saving and payback from your bill.
  • The system designer sizes a complete system — panels, inverter and battery — in about two minutes.

You can also see current complete system prices by size, and today's live panel rates per watt.

Or send us your monthly units on WhatsApp and we will size it for you and quote it itemised — panels, inverter, battery, structure and installation listed separately, so you can see exactly what you are paying for.