Electricity Bill Calculator

The Electricity Bill Calculator estimates what electricity costs in three ways: from a metered usage figure and tariff, from a single appliance's wattage and running hours, or from a list of appliances added together. Enter your rate per kilowatt-hour and the mode that matches your question to see the bill for the period and the equivalent cost per day, week, month, and year.

How It Works

1. Bill mode: You enter the kilowatt-hours used, the rate per kilowatt-hour, an optional daily supply charge, the number of days in the billing period (30 by default), and any fixed charge. Invalid or negative values, or a period of zero days, return an error.
2. Appliance mode: You enter one appliance's power in watts, how many hours it runs per day, and on how many days per week. The calculator converts watts to kilowatts, works out the average daily energy allowing for the days it does not run, and prices it.
3. Multi-appliance mode: Each appliance in your list gets the same treatment, producing its own daily energy, daily, monthly, and yearly cost, and the totals are summed across the list.
4. Period equivalents: Whatever the mode, totals are normalised: the per-day cost is multiplied out to a week, a month of 30.44 days, and a year of 365 days, so different billing periods can be compared fairly.

Formula

Bill mode:

$\text{Usage cost}=\text{kWh used}\times\text{Rate per kWh}$

$\text{Supply cost}=\text{Daily charge}\times\text{Days in period}$

$\text{Total}=\text{Usage cost}+\text{Supply cost}+\text{Fixed charge}$

Appliance modes:

$\text{Energy per day}=\frac{\text{Watts}}{1000}\times\text{Hours per day}\times\frac{\text{Days per week}}{7}$

$\text{Cost per day}=\text{Energy per day}\times\text{Rate per kWh}$

Monthly and yearly figures multiply the daily cost by 30.44 and 365 respectively, matching the annualisation used throughout this calculator.

Input Parameters

| Parameter | Unit | Typical range | Notes | |---|---|---|---| | Rate per kWh | Currency per kWh | 0.10 to 0.50 | Required in every mode; take it from your tariff or bill | | Usage | kWh per period | 100 to 3,000 | Bill mode; from your meter reading or last bill | | Daily supply charge | Currency per day | 0 to 2 | Bill mode; the fixed daily connection fee | | Billing days | Days | 7 to 365 | Bill mode; 30 or 31 reads as monthly, around 90 as quarterly | | Fixed charge | Currency | 0 and above | Bill mode; any one-off charge for the period | | Appliance power | Watts | 5 to 3,600 | Appliance modes; from the rating plate or manual | | Hours per day | Hours | Above 0 to 24 | Appliance modes; average running time, not plugged-in time | | Days per week | Days | 1 to 7 | Appliance modes; defaults to 7 |

Worked Example

Bill mode first: a home uses 850 kWh in a 30-day month at a rate of USD 0.30 per kWh, with a daily supply charge of USD 1.10 and a fixed charge of USD 5.

1. Usage cost: 850 x 0.30 = USD 255.00.
2. Supply cost: 1.10 x 30 = USD 33.00.
3. Total: 255 + 33 + 5 = USD 293.00 for the month.
4. Equivalents: per day 293 / 30 = USD 9.77; per week USD 68.39; per month on the annualised basis USD 297.40; per year USD 3,566.05.

Appliance mode second: a 2,000 watt heater running 5 hours a day, every day, at the same rate uses 2 x 5 = 10 kWh per day, costing USD 3.00 per day and USD 91.32 per month.

Interpreting the Results

In bill mode, compare the usage and supply lines: in the example, fixed charges add USD 38 to a USD 255 usage cost, which is why low-usage households feel supply charges so heavily and why cutting consumption alone cannot shrink a bill below the fixed floor. In appliance modes, the yearly column is the one that changes behaviour, because a small daily cost repeated 365 times is easy to underestimate; a heater at USD 3 a day is over USD 1,000 a year. The per-month figure uses 30.44 days, the average month length, so it will differ slightly from any single calendar month's bill.

Choosing the Right Tool

Use the Solar Battery Payback Calculator when the question flips from buying electricity to generating it: how long solar panels and a battery take to pay for themselves against bills like these. Use the Paint Calculator, the Tile Calculator, or the Concrete Calculator when you move from running costs to estimating materials for the renovation itself. Stay on this page for any question about what electricity consumption costs, whether for a whole home, one appliance, or a list of them.

Questions

Where do I find my rate per kilowatt-hour and daily supply charge?

Both are printed on your electricity bill and in your plan's tariff sheet or energy price fact sheet. If the plan has several rates, such as peak and off-peak, use the rate that applies to most of your usage, or run the calculator once per rate and add the results.

Why does my estimate differ from my real bill?

Real bills may add tiered pricing where the rate changes after a usage threshold, time-of-use pricing, demand charges, taxes, concessions, and solar feed-in credits, none of which this calculator models. It prices a flat rate plus the fixed charges you enter.

Does the appliance mode account for devices that cycle on and off?

Only through the hours you enter. A fridge is plugged in for 24 hours but its compressor runs part of that time, so enter its effective running hours, or use the daily kilowatt-hour figure from its energy rating label divided by your rate instead.

Limitations

The model uses one flat rate per kilowatt-hour and the fixed charges you supply. It does not handle tiered or block tariffs, time-of-use windows, demand charges, taxes and levies, concession discounts, or feed-in tariffs for exported solar, and appliance estimates depend on the wattage and running hours you enter rather than measured consumption. For a bill dispute or a plan comparison, work from the tariff documents and meter readings themselves.

Sources and Methodology

The calculation follows the standard structure of residential electricity billing used by utilities and energy regulators: energy charges from metered kilowatt-hours at the tariff rate, plus a daily supply charge and any fixed fees, with appliance consumption derived from rated power and running time. Annualisation uses 30.44 days per month, the average month length. Rates and charges are your inputs, taken from your own bill or tariff, so the methodology matches the way your retailer builds the bill even though individual tariff features differ.