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About this tool
See how many years a 5-star AC takes to pay back its price premium over a 3-star model, with tariff escalation.
The AC Star Rating Savings Calculator works out how long a higher BEE star rating takes to pay back its price premium, using each model's ISEER and the formula annual kWh = (tons x 3516.85 / ISEER) x hours x days / 1000. It compares the two units' yearly electricity, turns the difference into a rupee saving at your tariff, escalates that saving each year, and solves for the exact payback point as n = ln(1 + premium x g / first-year saving) / ln(1 + g). You also get lifetime net benefit, a year-by-year table, and the CO2 avoided at the Indian grid factor of 0.71 kg per kWh.
Open AC Star Rating Savings Calculator on AltFTool — it loads instantly in your browser.
Under Usage and tariff enter Capacity (ton), Hours per day, Cooling days per year, Tariff (per kWh) and Tariff rise per year (%).
Type the ISEER and Price for the Higher-rated model and the Model you are comparing with, or tap a preset chip such as 5-star (5).
Read Payback on the price premium against Years you will keep it, with the kWh saved per year, CO2 avoided per year and the year-by-year table.
You type the ISEER printed on the label, so the comparison reflects the actual model rather than a generic assumption about its star band.
Rising unit rates make an efficient unit pay back sooner, and the closed-form solution accounts for that instead of assuming a flat tariff forever.
Each year shows that year's saving, the running total and the net position against the premium, so you can see exactly when you break even.
ISEER is the Indian Seasonal Energy Efficiency Ratio: the cooling delivered over a season divided by the electricity used, so a higher number means less power for the same cooling. Star bands are just ranges of ISEER, and BEE revises those thresholds every few years — which is why yesterday's 5-star can become today's 3-star, and why the printed ISEER is the number to compare.
Roughly a quarter, for typical label values. At an ISEER of about 5.0 against about 3.7, the efficient unit draws around 26% fewer units for the same tonnage and running hours, because consumption is inversely proportional to ISEER. The rupee saving then depends entirely on your tariff and how many hours a year you run it.
No — it depends on running hours. The premium is recovered from usage, so a unit running eight hours a day for six months pays back far faster than one used a few weeks a year. If the calculated payback exceeds the years you expect to keep the AC, the cheaper unit is the better financial choice even though it uses more power.
Because ISEER is measured under standard test conditions. Real consumption rises with a lower thermostat setting, poor insulation, an oversized or undersized unit, dirty filters, frequent door opening and higher outdoor temperatures. Treat the figures here as a like-for-like comparison between two models, not a bill prediction — and check the current tariff slab with your discom.
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