Electricity Bill Calculator: Estimate Your Energy Cost
An electricity bill estimate combines the electricity you use with the price per kilowatt-hour, fixed charges, and an optional tax or levy. Enter values for the same billing period to calculate a flat-rate estimate and see how each part contributes to the total.
How to calculate an electricity bill
Multiply your metered usage in kilowatt-hours by the price charged for each kilowatt-hour. Add the total fixed charges for the period. This calculator then applies your entered tax percentage to that combined subtotal.
Energy cost = usage in kWh × price per kWh
Subtotal = energy cost + fixed charges
Tax = subtotal × tax rate ÷ 100
Estimated bill = subtotal + tax
All monetary inputs must use the same currency. The currency selector labels and formats amounts; it does not convert them using exchange rates. The default values are examples, rather than a tariff recommendation.
Example: 300 kWh at 0.15 per kWh
Suppose you use 300 kWh at a rate of 0.15 per kWh, have fixed charges of 10, and enter a 5% tax. Energy costs 300 × 0.15 = 45. Adding fixed charges gives a subtotal of 55. Tax is 55 × 5 ÷ 100 = 2.75, making the estimated bill 57.75.
With no tax, the same inputs give 55. With no fixed charges and no tax, the bill is just the energy cost of 45. If usage falls by 10% to 270 kWh while the other example inputs stay the same, the estimate becomes 53.025, displayed as 53.03 in a two-decimal currency.
What is a kilowatt-hour?
A kilowatt-hour, abbreviated kWh, is a unit of energy. It is the energy used by a device drawing one kilowatt of power for one hour. Watts and kilowatts describe power; kilowatt-hours describe energy consumed over time.
Energy in kWh = power in watts ÷ 1,000 × hours used
A device using 1,000 watts continuously for two hours consumes 2 kWh. A 100-watt device operating for ten hours uses 1 kWh. Actual appliances may cycle on and off, so rated power multiplied by time is an approximation when the power draw varies.
For a household bill, use metered or billed kWh for the period rather than one appliance’s wattage. When meter readings are already in kWh and no multiplier applies, usage is the current reading minus the previous reading.
How to enter fixed charges and tax
Fixed charges are amounts that do not depend directly on kWh used. Enter their total for the billing period. If your source lists a daily charge, multiply it by the number of billed days before entering it. For example, 0.30 per day over 30 days gives fixed charges of 9.
The tax field adds a percentage to energy cost plus fixed charges. Enter 0 if you are not adding a separate tax. This calculation does not determine a local tax rate or extract tax already included in entered prices.
If your bill taxes only some charges, contains several different levies, or includes separate credits, this simple model may not match every line item. Use inputs that reflect the calculation you intend to estimate.
Flat-rate estimates versus tiered and time-of-use bills
This calculator assumes one price per kWh for all entered usage. A tiered tariff applies different prices to different portions of consumption. A time-of-use tariff applies different prices according to when electricity is used.
For several rates, calculate each portion’s energy cost separately and add them. You can enter an effective average rate, calculated as total energy charges divided by total kWh, to reproduce that combined energy cost here. That average may change when the usage pattern changes.
The displayed average cost divides the entire estimated bill by usage. It includes fixed charges and tax, so it can be higher than the entered energy rate. With zero usage, that average is undefined and is shown as not applicable.
Frequently asked questions
Can the bill be positive when usage is zero?
Yes. Fixed charges, and tax on those charges under this model, can produce a positive bill even when no energy is used.
Should I enter my monthly usage?
Use usage for the period you want to estimate. Monthly, quarterly, or other periods work as long as fixed charges cover that same period.
Does this calculator look up electricity tariffs?
No. Supply your own price per kWh, fixed charges, and tax percentage from the figures you want to use.
Can I enter decimal values?
Yes. Usage, rate, and fixed charges can contain decimals. The tax percentage can also be a decimal from 0 to 100.
Why can rounded line items differ slightly from the total?
Intermediate values are kept unrounded and displayed amounts are formatted separately. Billing providers may round individual components at different stages.
Does it include solar export credits or demand charges?
No. There are no separate inputs for exports, credits, or peak demand. The model covers one energy rate, fixed charges, and one percentage tax.