METHODS · INDIA EDITION
How the India calculators work.
Cool Cost Lab uses a visible Indian retail-sizing convention and BEE label energy figures to create a shortlist. It is not an engineering heat-load calculation, an electricity-bill forecast or a product endorsement.
1. Room size estimate
The starting point is the retail shortcut of 1 ton per 100 square feet, shown as a ±10% band. This shortcut is not an official Bureau of Energy Efficiency load-calculation method. We add 10% for strong sun or a top floor, 0.33 ton for a kitchen and 0.05 ton for each regular occupant above two, then move to the next common sold size.
Worked example: 1.5 ton. A 120 sq ft room with two occupants and no extra heat gives a 1.08–1.32 ton range, so the tool shortlists the next common split label, 1.5 ton. Climate, ceiling height, windows, insulation and floor level can make a professional result materially different.
2. Running-cost estimate
BEE room-AC labels state annual electricity consumption for a standardized 1,600-hour operating basis. The calculator divides the reference annual kWh by 1,600 to estimate average watts, then applies watts ÷ 1,000 × hours/day × 30 × tariff/kWh. In the default 1.5-ton 3-star split example, 880 kWh ÷ 1,600 = 550 W; 8 hours/day at ₹8/kWh is about ₹1,056 per 30-day month.
3. 3-star versus 5-star payback
The reference pair is 880 versus 679 label kWh/year. The calculated reduction is 22.8%, rounded to a 23% scenario. With the default ₹11,500 price gap, 8 hours/day, ₹8/kWh and six cooling months, break-even is about 7.9 years. This is a scenario, not a guarantee; compare the current BEE labels of the exact two models.
Where the method stops
The tool stops beyond its single-room 2-ton product range. Multi-room spaces, unusual ceilings, major west glazing, weak insulation and extreme local temperatures need a qualified load calculation. State tariffs are slabbed and may include fixed charges, taxes or subsidies that this marginal-energy estimate does not model.
Primary sources
- Bureau of Energy Efficiency: Standards & Labelling — star-label purpose and the 1,600 annual operating-hours basis for room air conditioners.
- Bureau of Energy Efficiency: S&L appliance schedules — current program documents and schedules.
- Bureau of Energy Efficiency: QR-code verification portal — checking the label record for a specific model.
Method and links reviewed September 10, 2026. Product labels and BEE schedules change over time.