Electricity Bill Calculator

What does this Electricity Bill Calculator do?

This calculator estimates the monthly running cost of any single appliance, based on its power rating (in watts), how many hours a day you use it, how many days a month, and your utility's rate per unit.

The formula

Units consumed (kWh) = (Watts × Hours per day × Days per month) ÷ 1,000. Cost = Units × Rate per unit.

Step-by-step example

A 1,500-watt appliance used 4 hours a day for 30 days: units = (1,500 × 4 × 30) ÷ 1,000 = 180 kWh. At ₹8 per unit, cost = 180 × 8 = ₹1,440 for the month.

Tips & common mistakes

• Electricity meters and bills measure usage in kilowatt-hours (kWh), not watts — dividing by 1,000 to convert watt-hours to kilowatt-hours is an easy step to forget when calculating by hand.
• Your utility's rate per unit often changes at different consumption tiers (slab-based pricing) — this calculator uses a single flat rate, so treat the result as an estimate rather than an exact bill match.
• Standby power (devices left plugged in but "off") isn't captured here unless you know its specific wattage — many electronics still draw a small amount of power in standby mode.

Which appliances typically cost the most to run

High-wattage appliances used for extended periods — air conditioners, water heaters, and clothes dryers — are usually the biggest contributors to an electricity bill, while low-wattage devices like phone chargers and LED lights contribute comparatively little even when left on for long periods. Running this calculator for each major appliance separately can reveal which ones are actually worth targeting to reduce your bill.

Understanding tiered/slab electricity pricing

Many utilities charge a higher rate per unit once your monthly consumption crosses certain thresholds, rather than a single flat rate for all usage. This calculator uses one flat rate you provide, so for a precise bill match under tiered pricing, you may need to calculate usage within each tier separately.

Standby power: the hidden contributor to your bill

Many electronics continue drawing a small amount of power even when "off" but still plugged in — sometimes called phantom or standby load. Individually small, these can add up meaningfully across a household with many always-plugged-in devices (chargers, set-top boxes, game consoles) over a full month.

Comparing appliance running costs

Running this calculator separately for your major appliances (AC, water heater, refrigerator, washing machine) and comparing the results is a practical way to identify which specific appliances are actually driving your bill, rather than guessing based on which ones you use most often — usage duration and wattage together determine cost, not just one or the other.

A worked example: comparing two appliances

A 100-watt fan running 8 hours a day for 30 days: (100 × 8 × 30) ÷ 1000 = 24 kWh, costing ₹192 at ₹8/unit. A 1,500-watt AC running just 4 hours a day for the same period: (1,500 × 4 × 30) ÷ 1000 = 180 kWh, costing ₹1,440 — 7.5x more, despite running for half as many total hours, purely because of its much higher wattage.

Frequently asked questions