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Everyday · 6 min read · Last updated September 2026
Worked example — a 300 W fridge compressor actually runs ~8 h/day: 300 × 8 ÷ 1,000 = 2.4 kWh/day → 72 kWh/month → 576/month at 8 per unit. A 1.5 kW AC at 8 h/day: 1.5 × 8 × 30 = 360 kWh → 2,880/month. Same formula, five-fold difference — appliance wattage × runtime is where bills are decided.
Many utilities price in slabs: the first 100 kWh cheap, the next band pricier, and so on. Your average rate is not the rate for the next kWh — crossing into a higher slab makes every additional AC hour more expensive than your bill average suggests. Check your bill's slab structure before estimating savings; shaving consumption below a slab boundary saves at the higher marginal rate.
Wattage × runtime ranks them honestly: ACs, water heaters and dryers dominate; fridges run constantly but at low power; phone chargers and idle electronics are rounding errors despite folklore. Measure suspects with the appliance's nameplate wattage and your usage pattern in the Electricity Bill Calculator — and compare appliance upgrades with the Appliance Running Cost tool.
For each appliance: watts × daily hours ÷ 1,000 = daily kWh. Multiply by 30 for monthly kWh, sum across appliances, then multiply by your rate (respecting slab tiers if your utility uses them).
Wattage × hours × days × rate. A 1.5 kW split AC at 8 h/day and 8/unit: 1.5 × 8 × 30 = 360 kWh → 2,880 a month. Higher rates or longer runtimes scale it linearly.
Usually heating and cooling (AC, heaters), water heating and dryers — high wattage times long runtime. Always-on low-wattage devices like fridges matter, but chargers and idle electronics barely register.
Slab pricing (later units cost more), fixed charges, taxes and fuel-adjustment surcharges sit on top of the energy line. Check the bill’s non-energy lines before blaming the appliances.