Solar Panel Savings Calculator (Payback in Years)
Enter your monthly units and per-unit tariff to size an on-grid solar system — the recommended kW, how many panels, what it should cost in 2026, and how fast it pays for itself.
Solar Panel Savings Calculator
An average effective rate — check your LESCO/GEPCO bill for the slab that actually applies to you.
On-grid installed estimate 2026 — excludes batteries and civil work; update it from your own quotes.
About the Solar Panel Savings Calculator
Rooftops across Pakistan have turned into power stations, and the first question is always size: how many kilowatts does this house actually need? The honest input is your consumption, not your bill amount — units are printed on every LESCO, GEPCO and DISCO statement, and units are what panels must produce. This calculator turns that one number into a system size, a panel count and a price.
Sizing follows the installer rule of thumb: daily units = monthly units ÷ 30, and system kW = daily units ÷ 4.5 peak sun hours, rounded up. A home consuming 450 units a month burns 15 a day, which needs a 3.4 kW array after rounding up. Panels come whole — 550 W is the common modern size — and the cost is computed from the panel count × wattage × per-watt rate, because that is how real quotes are built.
Everything runs inside your browser with nothing stored or sent. Size a system before calling installers, check a quote against the maths, or test how a tariff rise shrinks the payback — and read the 25-year figure with its caption in mind: real arrays degrade and need maintenance, which the simple arithmetic leaves out.
How to Use the Solar Panel Savings Calculator
Follow these simple steps — the whole process takes under a minute:
- Enter monthly units — the kWh figure from a recent bill, or an average of the last few months.
- Set the per-unit tariff — the Rs. 60 default is an average effective rate; check your LESCO or GEPCO bill for your figure.
- Pick the panel wattage — 450, 550 or 600 W; 550 W is the common modern choice and the default here.
- Adjust cost per watt — Rs. 300 is an on-grid installed estimate for 2026; batteries push it much higher.
- Read the results — system size, panel count, installed cost, monthly savings, payback and the 25-year estimate.
The Formula & Method Behind the Solar Panel Savings Calculator
The sizing formula is system kW = monthly units ÷ 30 ÷ 4.5, rounded up to one decimal. The 30 turns a month into days, and the 4.5 is the peak-sun-hour assumption for much of Punjab — the hours a panel performs near rated output. For 450 units: 450 ÷ 30 = 15 units a day, and 15 ÷ 4.5 = 3.33, which rounds up to a 3.4 kW recommendation.
Panels come in whole units: panels = kW × 1000 ÷ panel wattage, rounded up. A 3.4 kW target is 3,400 W, and 3,400 ÷ 550 W = 6.18, so seven panels it is — an installed array of 3.85 kW, slightly above target because half panels do not exist. The cost then follows the panels rather than the rounded kilowatts: 7 × 550 W × Rs. 300 per watt = Rs. 1,155,000, the way an installer prices hardware watt by watt.
Savings and payback close the loop. Monthly savings = units × tariff — 450 × Rs. 60 = Rs. 27,000, the bill the array offsets when it covers your consumption. Payback = system cost ÷ monthly savings: 1,155,000 ÷ 27,000 = 42.8 months, about 3.6 years. The 25-year view multiplies the monthly saving across 300 months and subtracts the system cost: 27,000 × 300 − 1,155,000 = Rs. 6,945,000 — before panel degradation, cleaning and inverter replacement, and before any tariff rise, which would only shorten the payback.
Solar in Pakistan — Sizing, Net Metering and the Fine Print
Start from units, not rupees. Bills move with slabs and fuel adjustments, but units are physical consumption — the thing panels must replace. Pull the kWh figure off your last statement, or estimate what a typical month consumes with the electricity bill estimator, then size from there. A system sized to rupees drifts; one sized to units holds.
Net metering changes the maths. A grid-tied array exports surplus units by day and draws them back by night, and the utility credits the difference — which is why an on-grid system at Rs. 300 per watt undercuts battery hybrids. Savings invested rather than spent compound too: the compound interest calculator shows what a monthly surplus becomes at bank rates.
Financing the array. Many households fund solar through a top-up loan rather than a lump sum, and the test is the same as any borrowing: does the instalment fit beside the bill it replaces? The EMI calculator turns a loan size and rate into the monthly instalment to compare against Rs. 27,000 of savings.
Panels are priced in dollars. Modules and inverters track the rupee, so a sharp currency move shifts the per-watt figure between your first survey and the final invoice — check the drift with the currency converter before signing, then type the new rate into the editable cost-per-watt box and watch the payback move.
Frequently Asked Questions
Quick answers about the Solar Panel Savings Calculator — for anything else, message us on WhatsApp.
How is the recommended system size calculated?
From consumption: monthly units ÷ 30 gives daily units, divided by 4.5 peak sun hours gives kilowatts, rounded up to one decimal. A 450-unit home consumes 15 units a day and needs 15 ÷ 4.5 = 3.33, so the calculator recommends a 3.4 kW system.
Why does a 3.4 kW system need seven panels?
Panels come whole: 3.4 kW is 3,400 W, and 3,400 ÷ 550 W = 6.18, which rounds up to seven 550 W panels — an installed array of 3.85 kW. A bigger 600 W panel would need six, and a smaller 450 W panel would need eight.
Why is the cost computed from panels instead of the kW figure?
Because installers price hardware watt by watt: the invoice reads panel count × wattage × cost per watt. At the defaults that is 7 × 550 × 300 = Rs. 1,155,000 — slightly different from a 3.4 kW shortcut, and closer to what a real quote contains.
What payback should I expect?
At the defaults — 450 units at Rs. 60, 550 W panels at Rs. 300 per watt — the Rs. 1,155,000 system saves Rs. 27,000 a month and pays back in 42.8 months, about 3.6 years. A higher tariff shortens it; a shaded roof or a cheaper quote moves it either way.
What does the 25-year savings figure leave out?
It is the simple arithmetic — Rs. 27,000 × 300 months − Rs. 1,155,000 = Rs. 6,945,000 — before panel degradation of roughly half a percent a year, cleaning, and an inverter replacement past year ten. Rising tariffs push the real figure the other way, which is why the caption matters.
Does this include batteries or net metering?
The estimate assumes an on-grid system at Rs. 300 per watt — no batteries. Adding storage lifts the cost per watt sharply, while net metering credits exported surplus and keeps the on-grid maths honest. Check your DISCO net-metering terms before relying on exports.
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