How to use the solar system calculator
- 1 Enter your average monthly units from recent bills.
- 2 Choose the panel size, such as 585 W.
- 3 Enter the installed cost per kW quoted by installers.
- 4 Enter your rate per unit to see savings and payback.
Worked example
A home using 600 units a month. The system size is about 5.3 kW: nine 585 W panels and a 6 kW inverter, needing about 250 sq ft of roof. At Rs 100,000 per kW the cost is about Rs 526,500, and at Rs 60 per unit it saves about Rs 36,000 a month, paying back in about 1.2 years.
Choosing a solar setup
- On-grid systems are cheapest and save the most during the day, but switch off during loadshedding for safety.
- Hybrid systems add batteries, so you keep power during outages; batteries add cost and need replacing after some years.
- Panels and inverter: Tier 1 panels and a reputable inverter brand matter more than the lowest price per watt.
- Output varies: production is highest in spring and summer and lower in foggy winter months in Punjab.
Exporting surplus units? See the saving under net billing with the Solar Net Billing Calculator. For backup only, the UPS Backup Calculator may be enough.
Features
Sized for Pakistan
About 120 units a month per kW, based on 5 sun hours and 80% efficiency.
Complete system
Panels, inverter and roof space.
Payback
Years for savings to cover the cost.
When to use it
Planning solar
Know what size to ask installers for. See net billing savings with the Solar Net Billing Calculator.
Comparing quotes
Check whether a quote matches your needs. See your current bill with the Electricity Bill Calculator.
Net metering
Combine with the net billing calculator. Backup only? Try the UPS Backup Calculator.
Budgeting
Estimate the cost before you buy. See what uses most with the Appliance Running Cost Calculator.
Related Bills and Energy tasks
Frequently asked questions
How many units does 1 kW of solar produce in Pakistan?
Roughly 120 to 140 units a month on average, more in summer and less in winter and fog.
What size system do I need?
Divide your monthly units by about 120 to get kW. A home using 600 units a month needs about 5 kW.
How many panels do I need?
System size in watts divided by panel watts. A 5 kW system needs nine 585 W panels.
What inverter size should I choose?
Equal to or slightly above the panel capacity. Hybrid inverters can also charge batteries.
How much roof space is needed?
About 25 to 30 sq ft per panel, so roughly 100 sq ft per kW.
How long does solar last?
Panels usually carry 25-year performance warranties. Inverters often last 8 to 12 years.
Do I need batteries?
Only for backup at night or during loadshedding. On-grid systems with net billing do not need batteries.
Does cleaning matter?
Yes. Dust can cut output by 10% to 25%, so clean panels regularly.
Should I choose on-grid, hybrid or off-grid?
On-grid systems are cheapest and work with net billing. Hybrid systems add batteries for backup. Off-grid systems work without the grid but need large batteries.
What are Tier 1 panels?
Panels from well-known manufacturers with a strong financial track record. Many installers in Pakistan offer them.
How much does solar save in winter?
Production falls in winter and on foggy days, so savings are lower than in summer.
Do I need permission to install solar?
On-grid systems need DISCO approval for a net meter. Off-grid systems do not.
Can I install solar on a rented house?
Yes, with the owner's permission, but plan for removal if you move.
Results are estimates based on the official rates linked above. Confirm important figures with the issuing authority or a qualified adviser before you act on them.
Built and reviewed by Hamza Farooq, founder and lead developer
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