3 Star vs 5 Star AC: The Payback, Worked Out in Rupees

BEE's star label for ACs is based on ISEER — the Indian Seasonal Energy Efficiency Ratio, the cooling delivered per unit of electricity across a typical Indian temperature profile. A higher ISEER means a lower bill for the same cooling. The label also declares annual units, measured over a 1,600-hour season: roughly 5 hours a day for 11 months, or 8 hours a night for six or seven.

Because BEE periodically tightens the ISEER needed for each star, a label is comparable only with others from the same label year.

Panasonic sells a 3-star and a 5-star 1.5 ton unit with the same smart features, which makes a clean comparison.

• Buy 5-star: a bedroom AC run all night for most of the summer, a home office, a shop or clinic, or a home on a high electricity slab.
• Buy 3-star: a living room used in the evenings, a guest room, a rented home you will leave in two or three years, or a tight budget.
• Either way: choose the higher ISEER within your star, and check the rated capacity suits the room — an undersized 5-star unit running flat out loses its efficiency advantage.