Electricity Bill Calculator

This tool turns three numbers you can find in a minute — an appliance's wattage, how many hours a day it runs, and the rate you pay per unit of electricity — into a running-cost estimate for any billing period. It shows the energy consumed in kilowatt-hours (kWh, the “units” on your meter), the consumption charge, an optional fixed or standing charge, and any tax or duty, then adds them into an estimated total bill.

It works for a single device or a whole home: enter one appliance's wattage to see what that device costs, or use your average total household load to sketch a monthly bill. The arithmetic is currency-agnostic, so you can enter your rate in any currency and read the result back in the same units.

Every figure comes from one short chain of arithmetic:

energyKwh = (watts × hours/day × days) ÷ 1000
consumptionCharge = energyKwh × ratePerKwh
tax = (consumptionCharge + fixedCharge) × taxPercent ÷ 100
totalBill = consumptionCharge + fixedCharge + tax

The only unit conversion is dividing watt-hours by 1,000, because one kilowatt is exactly 1,000 watts. A device's power (watts) tells you how fast it draws energy; multiplying by time (hours) gives the energy actually used. That is why a low-wattage device left on all day can cost more than a high-wattage one used for minutes — it is power × time that you pay for, not power alone.

A 1,500 W space heater running 4 hours a day for a 30-day month, at $0.20/kWh with a $10 standing charge and 8% tax. Every value below is produced by the same engine that powers the calculator, so the walk-through can never disagree with the tool.

A quick reference for common household loads, with the monthly kWh and running cost computed at a flat $0.17/kWh over 30 days. Your own numbers will differ with your rate and actual hours of use — swap them into the calculator above for a figure specific to you. Nameplate wattages for cycling appliances such as fridges and air conditioners are shown as an average continuous draw, which is lower than the peak.

Want to see the payback from swapping to lower-wattage lighting? The LED savings calculator compares old and new bulbs over time, and the amps to watts calculator helps when a device only lists its current draw and voltage instead of a wattage.

Because cost is power × time × rate, there are only three levers that move a bill: run fewer watts, run them for less time, or pay a lower rate. In practice a few habits account for most of the savings available to an average household:

• Target the biggest loads first. Heating and cooling are the largest annual uses of electricity in a typical home, with air conditioning consistently the single largest end use — a well-set thermostat and good insulation move the needle far more than unplugging a phone charger.
• Cut hours, not just watts. A high-wattage appliance used briefly (a kettle, a hair dryer) usually costs less over a month than a lower-wattage device left running around the clock — check the “Hours/day” column above before assuming a device is cheap to run.
• Chase standby (“phantom”) load. Routers, chargers and electronics in standby draw power continuously even when idle; a power strip you switch off at night removes that hours-per-day entirely rather than just reducing it.
• Switch to efficient lighting and appliances. An LED bulb draws roughly a quarter of an equivalent incandescent bulb's wattage for the same light output — swap the wattage in the calculator above to see the effect on your own numbers, or use the LED savings calculator for a full old-vs-new bulb comparison.
• Check for a time-of-use or off-peak rate. If your utility charges less at certain hours, shifting laundry, dishwashing or EV charging to those windows lowers the effective rate without changing usage at all.

This is an estimate built on a deliberately simple model. Keep these assumptions in mind:

• The load is assumed to draw its rated (nameplate) wattage constantly for the stated hours — duty-cycling, standby draw, motor start-up surge and power factor are ignored, so thermostat-controlled appliances usually use less in reality.
• A single flat per-kWh rate is applied. Tiered/slab pricing, time-of-use rates and demand charges are not modelled — calculate each tier or period separately and add the results.
• Tax is applied to the whole pre-tax subtotal (consumption + fixed charge). Some utilities tax only the energy charge or exclude standing charges; this is a simplifying convention, not a cited legal rule.
• Real bills can add fuel/power-cost adjustment surcharges, minimum charges and region-specific levies this model does not capture.
• Default rates are national averages; read your own per-kWh rate off a recent bill for the most accurate result.