Star rating and heat pump payback calculator

How to use it. Enter the price difference between the two models you are comparing, not the full price. If a store or DISCOM programme gives a specific benefit only on the efficient model, enter it as the discount. For the annual saving, take the difference in annual units between the two BEE labels, scale it to your own hours of use, and multiply by the rate per unit in your highest slab.

Formula. Net extra cost = price difference − discount. Each year's saving grows by the tariff rise you enter. Payback is the point where cumulative savings equal the net extra cost. Net saving over the period = total savings within the horizon − net extra cost.

Worked example (illustrative). A 5-star 1.5-ton inverter AC costs ₹8,000 more than a 3-star model. Label figures scaled to 1,200 hours a year suggest it uses 250 fewer units a year. At ₹7.20 per unit that is ₹1,800 in year 1. With tariffs rising 3% a year, payback is a little over 4 years, and the net saving over 10 years is roughly ₹12,600.

Limits. Savings depend heavily on hours of use: a guest-room AC used 200 hours a year may never pay back a costlier model. Labels are measured under standard test conditions. The same calculator works for a heat-pump water heater against an electric geyser; enter the price gap and the yearly unit difference. Figures are illustrative.