# Solar calculator: how many solar plates does your home need?

URL: https://which.pk/solar/tools/solar-calculator/
Author: Hassam Imtiaz
Updated: 10 Oct 2026

## Summary

Add your fans, lights, ACs, fridge and other appliances, pick your city, and the calculator works out your daily and monthly units, the kW of solar panels you need, how many 585 W or 650 W plates that is, the smallest inverter that fits, and the roof space. It uses Global Solar Atlas output for six cities: 1 kW of panels makes about 4.0 units a day in Lahore and 4.65 in Karachi. The higher result allows for rooftop heat, dust and shade.

## Key facts

- Lahore output: 4.0 units/kW/day
- Karachi output: 4.65 units/kW/day
- 585 W panel: about 28.5 sq ft

**Pick your city, tap in your appliances, and the calculator shows how many solar plates (panels) you need.** In Lahore, 1 kW of panels makes about 4.0 units a day, so a home using 500 units a month needs roughly 4.1 to 5.2 kW: that's 8 or 9 plates of 585 W. Every figure updates as you tap.

## How does the solar calculator work?

It adds up what your appliances use in a day, then divides by what 1 kW of panels makes in your city.

1. **Daily units.** For each appliance: watts × hours a day × how many, divided by 1,000. A fridge's compressor switches on and off, so we use its daily units, not its rated watts. You can change any wattage or hours to match your own appliance's label.
2. **Monthly units.** Daily units × 30. Compare this with the units on your electricity bill: if they are far apart, adjust the hours.
3. **kW of panels.** Daily units ÷ units per kW per day in your city. That's the low figure. The high figure divides by 80% of that output, our allowance for a rooftop that is hotter, dustier and less ideally angled than the measured sites.
4. **Number of plates.** kW × 1,000 ÷ the plate's wattage, rounded up.
5. **Inverter.** The smallest common size that covers both the panels and everything you listed running at once.
6. **Roof space.** Number of plates × the plate's area from the maker's datasheet, plus the same figure in marla at 225 sq ft.

## Where do the appliance wattages come from?

The starting figures are typical ratings from spec sheets of models sold in Pakistan, checked on 10 Oct 2026. Ceiling fans are about 75 W (four conventional models) and inverter fans 30 W to 55 W, depending on speed. For inverter ACs we use the middle rated cooling input of three models each: 1,100 W for 1 ton and 1,600 W for 1.5 ton (Gree, TCL, PEL and Orient). Haier rates three of its inverter fridges at 1 unit a day.

Treat the AC figures as an upper guide, because an inverter AC draws less once the room has cooled. For a deep freezer we assume the compressor runs about half the day. A 1 HP pump is 746 W by definition. Change any figure to match the label on your own appliance.

## How much does 1 kW of solar make in each city?

These are long-term yearly averages from the Global Solar Atlas, a World Bank tool using Solargis data. They assume panels at the best tilt, cleaned regularly, with 3.5% loss to dust and 7.5% to wiring and inverters.

| City | Units per kW per year | Units per kW per day |
|---|---|---|
| Lahore | 1,466 | 4.0 |
| Islamabad | 1,559 | 4.27 |
| Peshawar | 1,502 | 4.12 |
| Multan | 1,592 | 4.36 |
| Karachi | 1,697 | 4.65 |
| Quetta | 1,936 | 5.3 |

Output also changes through the year. In Lahore, December and January make roughly two-thirds of what March to May make, so a system sized on the yearly average will fall short on winter days and run ahead in spring.

## What the calculator doesn't tell you

- **Net billing limits the size.** If you want to export to the grid, NEPRA's 2026 rules cap the system at your sanctioned load. See [net metering in Pakistan](/solar/guides/net-metering-pakistan/).
- **Batteries are separate.** Panels cover daytime use. For running things at night, see [lithium battery prices](/solar/guides/lithium-battery-price-pakistan/).
- **Shade matters more than anything.** A water tank or a neighbour's wall shading part of the roof can cut output well below these figures.

For prices, see [solar system price in Pakistan](/solar/guides/solar-system-price-pakistan/), and for the full method with a worked example, [what size solar system you need](/solar/guides/what-size-solar-system/).

## Questions people ask

### How many solar plates are required for a 5kW system?

Nine 585 W plates make 5.3 kW, and eight 650 W plates make 5.2 kW. Divide 5,000 watts by the plate's wattage and round up.

### How many units does 1 kW of solar make in Pakistan?

On average over a year, about 4.0 units a day in Lahore, 4.27 in Islamabad, 4.65 in Karachi and 5.3 in Quetta, from Global Solar Atlas data. Winter days make less and rooftops lose some output to heat, dust and shade.

### How much roof space do I need for solar plates?

A 585 W plate is 2335 x 1134 mm, about 28.5 sq ft. Nine of them, about 5 kW, need roughly 257 sq ft before gaps for walking and wiring.

## Sources

- [Global Solar Atlas site data: Lahore](https://api.globalsolaratlas.info/data/lta?loc=31.5204,74.3587), Global Solar Atlas (World Bank / ESMAP, data by Solargis) (accessed 10 Oct 2026)
- [Global Solar Atlas site data: Karachi](https://api.globalsolaratlas.info/data/lta?loc=24.8607,67.0011), Global Solar Atlas (World Bank / ESMAP, data by Solargis) (accessed 10 Oct 2026)
- [Global Photovoltaic Power Potential by Country (2020)](https://documents1.worldbank.org/curated/en/466331592817725242/txt/Global-Photovoltaic-Power-Potential-by-Country.txt), World Bank / ESMAP (accessed 10 Oct 2026)
- [Tiger Neo N-type 72HL4R-(V) 560-585 W datasheet](https://solarproof.com.au/datasheets/panel_datasheet_JKM560-585N-72HL4R-V-F2C1-EN-AU-CEC.pdf), JinkoSolar (accessed 10 Oct 2026)
- [Hi-MO 9 product page](https://www.longi.com/en/products/modules/hi-mo-9/), LONGi (accessed 10 Oct 2026)
- [NEPRA (Prosumer) Regulations, 2026 (S.R.O. 251(I)/2026), Wayback Machine copy](https://web.archive.org/web/20260209155326/https://www.nepra.org.pk/Legislation/3-Reg/3.35%20NEPRA%20%20Prosumer%20Regulations%202026/NEPRA%20Prosumer%20Regulations%20(SRO%20251(I)2026)%2009-02-26.PDF), NEPRA (accessed 10 Oct 2026)
- [GFC Nabeel and Aeromax ceiling fan specifications](https://www.gfcfans.com/products/nabeel), GFC Fans (accessed 10 Oct 2026)
- [Gree 1.5 ton inverter split AC GS-18PITH11S specifications](https://japanelectronics.com.pk/products/gree-split-ac-inverter-1-5-ton-gs-18pith11s-aaa), Japan Electronics (retailer listing of Gree specs) (accessed 10 Oct 2026)
- [Haier HRF-346IPPA inverter refrigerator](https://www.haier.com/pk/refrigerators/hrf-346ippa.shtml), Haier Pakistan (accessed 10 Oct 2026)