01 · FAQ
How many units does a 1.5 ton AC use?
An inverter 1.5 ton AC running 8 hours uses about 7 to 8 units a day, or roughly 230 a month. A non-inverter unit uses about 11 to 12 a day for the same hours.
Mastoor Energy · Calculator
Solar load calculator
List what you run and for how long. The calculator works out your daily units and peak load, then sizes the panels, inverter and battery for your city.
How to use it
Three inputs per appliance
- Pick the applianceTypical running watts are filled in. Change them if your rating plate says otherwise.
- Set quantity and hoursHours per day it is switched on, and days per week.
- Say when it runsDay, night or both. This decides how much solar you can use directly.
- Choose the system typeHybrid adds a battery sized for the backup hours you enter.
- Read the resultThen carry it into the cost and ROI calculators with one tap.
Method
How the calculator works
Daily units. For each appliance: watts × quantity × hours × days per week ÷ 7, divided by 1,000. Appliances with a compressor or thermostat do not draw full power the whole time they are on, so the calculator applies a duty factor: about 35% for a refrigerator and 60% for an inverter air conditioner.
Peak load. The sum of everything you listed, multiplied by 0.7, because not every appliance runs at the same moment. This sets the minimum inverter size for a hybrid system.
System size. Monthly units ÷ (yield per kW per day × 30.4 days). Yield comes from the Global Solar Atlas for your city, less 10% for dust and real-world losses. In Karachi that is about 4.2 units per kW per day. The size is rounded up to whole 585 W panels.
Roof space. About 36 square feet per panel, which includes the gaps between rows.
Battery. Backup hours × about half your peak load, divided by the usable share of a lithium battery, rounded up to 5.12 kWh units.
Daytime share. Day appliances count 85% as daytime use, day-and-night appliances 40%, and night appliances 5%. Under net billing this number matters, because solar you use yourself is worth four to five times what you earn by exporting it.
Reference
Typical appliance wattage in Pakistan
The defaults used in the calculator. Check the rating plate on your own appliance for the exact figure.
| Appliance | Running watts | Typical units a day |
|---|---|---|
| Ceiling fan (standard) | 80 W | 1.1 (14 hours) |
| Ceiling fan (inverter, DC) | 35 W | 0.5 (14 hours) |
| LED bulb | 12 W | 0.07 (6 hours) |
| Refrigerator | 180 W | 1.5 (cycles all day) |
| AC 1 ton (inverter) | 1,100 W | 5.3 (8 hours) |
| AC 1.5 ton (inverter) | 1,600 W | 7.7 (8 hours) |
| AC 1.5 ton (non-inverter) | 1,800 W | 11.5 (8 hours) |
| AC 2 ton (inverter) | 2,200 W | 10.6 (8 hours) |
| Water pump (1 HP) | 750 W | 0.75 (1 hour) |
| Washing machine | 500 W | 0.5 (1 hour) |
| Iron | 1,000 W | 0.25 (30 minutes) |
| Electric geyser | 3,000 W | 3.2 (90 minutes) |
| LED TV (43 inch) | 80 W | 0.4 (5 hours) |
| Deep freezer | 200 W | 1.9 (cycles all day) |
Questions
Load calculator FAQ
02 · FAQ
How many panels do I need for 500 units a month?
In Karachi, about 4 kW: seven 585 W panels. Cities with less sun need a little more. Enter 500 under 'I know my monthly units' to see it for your city.
03 · FAQ
What does a system this size cost?
Tap 'Estimate the cost' to price your result. For standard sizes, see the price guides for 3 kW, 5 kW, 10 kW, 15 kW and 20 kW systems.
04 · FAQ
Should the system cover 100% of my use?
Under net billing, exported units earn about Rs 11 while the units you buy cost far more. A system sized near your daytime use, with a battery to shift some solar into the evening, often gives a better return than one sized to export a lot.
05 · FAQ
Why is my bill estimate different from my actual bill?
The estimate uses the non-protected residential tariff with current adjustments and a 3 kW sanctioned load. Your own sanctioned load, municipal charges and tax status will move it. The bill calculator lets you set these.
Next
Price it and check the payback
Calculator · Mastoor Energy
Solar system cost calculator
Estimate the cost of a solar system in Pakistan at November 2026 market rates: panels by brand, inverter, lithium batteries, structure, cabling and installation, itemised.
Open →Calculator · Mastoor Energy
Solar ROI calculator
Enter your electricity bill and solar system cost to see the monthly saving, payback period and 25-year return in Pakistan under the 2026 net billing rules.
Open →Guide · Mastoor Energy
On-grid vs hybrid vs off-grid solar: which system do you need?
How on-grid, hybrid and off-grid solar systems differ, which one keeps the power on during load-shedding, and how to choose for a home or business in Karachi.
Open →Enquire
Send us your load
Share your result on WhatsApp and we will check the sizing against your roof and wiring, then quote.