How Much Solar Do I Need? Size Your System From Your LESCO or IESCO Bill

Your electricity bill is the best sizing tool you already have. It shows how many units you use, how they change through the year, your sanctioned load and which tariff you're on. Those four things decide what size of solar system makes sense far better than a guess like "a 5 kW system for a normal house". This guide shows how to read them, turn them into a system size, and check that the size in your quote fits. It works for any DISCO bill, but the examples use LESCO and IESCO because those are the bills we're asked about most.

The short answer

In Pakistan, each kW of solar panels makes about 108 units a month on average, using our planning figure of 3.6 units per kW per day. So:

System size in kW ≈ your monthly units ÷ 108

Use your summer units, not your average, if you want solar to keep up when the bill is highest. Then check two limits before you settle on a number: your sanctioned load (under net billing the system can't be bigger than it) and your roof space.

The rest of this guide explains each step.

Step 1: Find your units on the bill

LESCO, IESCO and the other DISCO bills print a table of your units for each of the last 12 months, next to the current reading. That history is what you need. Write down:

• Your highest month, usually June, July or August.
• Your lowest month, usually December or January.
• The yearly average: add all 12 months and divide by 12.

If your bill is on time-of-use (ToU) rates, it shows peak and off-peak units separately. Add them together for sizing, but keep the peak figure, because it matters later.

You can see how your current units turn into rupees, slab by slab, with the LESCO bill calculator or the IESCO bill calculator. Other DISCOs are on the electricity bill calculator page.

Step 2: Turn units into kW

Divide your chosen monthly units by 108. A few reference points, using the same maths as our system price pages:

• A 3 kW system makes about 324 units a month.
• A 5 kW system makes about 540 units a month.
• An 8 kW system makes about 864 units a month.
• A 10 kW system makes about 1,080 units a month.
• A 12 kW system makes about 1,296 units a month.

These are yearly averages. Panels make more in the long, bright days of April to June and noticeably less in winter, especially in Lahore and the rest of Punjab when smog and fog cut the sunlight. Dust on the panels cuts it too, so plan on cleaning them.

Which month should you size for?

• Size for your average if you mainly want to cut the yearly bill and you're fine with a higher bill in peak summer.
• Size closer to your summer peak if your summer bills are the problem. You'll export more in winter, but under net billing those exports are worth much less, as the next step explains.

Most homes end up somewhere between the two. The solar calculator helps here: choose your actual appliances and hours and it sizes the system for summer and winter separately.

Step 3: Adjust for net billing

This is where many quotes go wrong. New rooftop systems are now on net billing: units you take from the grid are charged at your normal tariff, but units you send to the grid are credited at only about Rs 8.13 each. Our guide to net metering vs net billing has the details.

That gap changes how you should size:

• Solar only saves you the full tariff on units you use while the sun is up. If your monthly bill is around 300 units, each grid unit costs you Rs 33.10 before taxes, while an exported unit earns Rs 8.13. That's Rs 24.97 less per unit.
• Your evening and night units still come from the grid, even with a system that matches your monthly total on paper. The export credit only covers part of that cost.
• So a system sized to "100% of my units" won't bring the bill to zero. Our system price pages assume about 60% of what a well-sized system makes is used in the home during the day, with the rest exported.

Two practical consequences:

1. Oversizing pays less than it used to. Every extra kW beyond your daytime use mostly earns the export rate.
2. Shifting load into the day helps more than adding panels. Running the washing machine, iron, water pump and ACs while the sun is up can be worth more than another two panels.

If most of your use is in the evening, a hybrid system with batteries may suit you better than a bigger on-grid one. See hybrid vs on-grid inverter.

Step 4: Check your sanctioned load

Your sanctioned load is printed on your bill in kW. Under NEPRA's 2026 prosumer rules, your solar system can't be larger than it. If the size you worked out is bigger than your sanctioned load, you have two options: install a smaller system, or apply to your DISCO to increase the load first.

Increasing the load can move you onto a different tariff. A sanctioned load of 5 kW or more is billed on time-of-use rates: Rs 46.85 per unit in the four peak hours and Rs 34.53 off-peak, plus a fixed charge of Rs 675 per kW on half your sanctioned load. On ToU, your evening peak units are the most expensive ones, and solar can't cover them without batteries. Our guide to three-phase vs single-phase solar explains what larger loads mean for your connection and inverter.

Step 5: Check your roof

Each kW of panels needs roughly 5.5 to 6 square metres (60 to 65 sq ft) of roof that gets sun for most of the day. A 5 kW system needs around 28 square metres (300 sq ft), and a 10 kW system twice that. Water tanks, stair rooms, parapet walls and taller buildings next door all take space or cast shade. If you're short of space, a raised frame can help, but it adds cost. See elevated solar structure cost.

Worked examples

These use the same tariff as our bill calculators (un-protected rates, before fuel and quarterly adjustments). Your actual bill will differ with FPA, QTA and your exact category.

A home using about 300 units a month

A 300-unit bill on a 3 kW load comes to about Rs 14,100 including GST and the debt-servicing surcharge. Dividing 300 by 108 gives about 3 kW. If summer bills climb to 450 or 500 units, a 4 to 5 kW system covers more of that peak. Today a 3 kW on-grid system costs about Rs 269,960 – 360,387 installed, and a 5 kW system about Rs 399,840 – 567,880. See the 5 kW system price guide.

A home using about 500 to 600 units a month

At 500 units on a 4 kW load, the bill is about Rs 27,246. The rule points to roughly 5 to 6 kW, and the fixed charge alone reaches Rs 675 per kW once you pass 500 units. Check your sanctioned load before you size up: if it's below 5 kW, a system larger than the load needs a load increase first, which also moves the bill to ToU. Compare the 5 kW and 6 kW price pages.

A home using about 1,000 units a month

A home using 1,000 units usually has several ACs and is often already on ToU with a three-phase connection. The rule points to about 9 to 10 kW. A 10 kW on-grid system currently costs about Rs 785,480 – 1,195,161, and our estimate puts the saving at about Rs 27,218 a month, a payback of ~3.0 years. Because so many of those units are in the evening peak, many homes at this size add batteries. Read the 10 kW guide and the 12 kW guide.

If you're a protected consumer

If you've used 200 units or less in each of the last six months, you're billed at much lower protected rates. Going over 200 in any single month makes you un-protected for the next six months. Solar can help you stay under 200 in summer, but the saving per unit is small at protected rates, so payback is slower. Do the sums with the LESCO or IESCO bill calculator before you spend on a large system.

Check the size in your quote

When a quote arrives, check three things:

• Panel kW matches what your units point to, not just a round number the installer prefers.
• The inverter is rated close to the panel kW. Installers usually pair panels with an inverter of the same or slightly larger size.
• The system isn't larger than your sanctioned load, or the quote clearly includes the load extension.

Then run the quote through Check my quote, which compares each line against today's market prices. Live panel rates, currently Rs 38.0–42.2 per watt, are on the panel price page, and you can find nearby installers in our installer directory.

اس گائیڈ کی قیمتیں ہماری ٹریک کردہ ڈیلر لسٹنگز سے خود اپڈیٹ ہوتی ہیں (آخری تازگی 21 October 2026)۔ اشارہ جاتی مارکیٹ رینجز ہیں، کوٹ نہیں۔Prices update automatically from dealer listings we track (last refreshed 21 October 2026). Indicative ranges, not quotes.