Electricity Cost Guides
The calculator gives you a number. These guides explain where that number comes from, how to make it more accurate, and what to do about it.
Most of the confusion about electricity costs comes from three gaps. People do not know what their real price per kilowatt-hour is, because the bill buries it under supply, delivery and fixed charges. They do not know how many watts an appliance really uses, because the label shows a maximum rather than an average. And they do not know which of the fifty things plugged in at home actually matter, so effort goes into unplugging phone chargers while the water heater and an old garage fridge quietly do the damage.
Each guide below closes one of those gaps. They are written for homeowners and renters, not engineers, and every one of them links back to the electricity cost calculator so you can put your own numbers in as you read. Where we quote a rate, it is the U.S. Energy Information Administration's residential average for June 2026 (18.34¢ per kWh nationally) unless a state is named.
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How to Read Your Electricity Bill and Find Your Real Rate
Where supply, delivery and fixed charges hide on a US electricity bill, how to work out your true cents-per-kWh rate, and which number to use.
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Electricity Rates by State (June 2026 EIA Data)
Every US state ranked by average residential electricity price per kWh, from Nevada at 13.11¢ to Hawaii at 52.72¢, and what the gap means for you.
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How Many Watts Do Appliances Use? Full Wattage Chart
Typical wattage, hours of use and monthly cost for 80+ household appliances, from space heaters and AC to fridges, TVs, EV chargers and LED bulbs.
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Phantom Load: What Standby Power Really Costs You
How much electricity devices use when they are off, which ones are worth unplugging, the one-watt rule for annual cost, and what to leave alone.
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Time-of-Use Electricity Rates: When Power Is Cheapest
How time-of-use electricity plans work, typical peak and off-peak prices, which appliances to shift, and whether a TOU plan would save you money.
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The 10 Most Expensive Appliances to Run, Ranked
Ranked by real monthly cost at the US average rate: central AC, water heaters, EV chargers, dryers, hot tubs and old fridges, with one fix for each.
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How to Measure What an Appliance Really Uses
Four ways to find an appliance's real electricity use: the label, the EnergyGuide sticker, a $25 plug-in meter and your smart meter's hourly data.
Where to start
If you only read one, make it how to read your electricity bill. Finding your true marginal rate turns every estimate on this site from a national average into your number. After that, the most expensive appliances to run tells you where the money actually goes, and the wattage chart is the reference to keep open while you work through the house.
If your utility has moved you onto a time-of-use plan, or you are thinking about an electric car, read time-of-use rates explained before anything else; on those plans, when you use electricity matters as much as how much.
Frequently asked questions
Who writes these guides?
The WattPenny editorial team, an independent publisher with a software and engineering background. Every figure is sourced from the U.S. Energy Information Administration, the Department of Energy, ENERGY STAR or manufacturer specifications, and the calculators use the same data. See the About page for our editorial standards.
How often is the rate data updated?
The EIA publishes state average residential prices monthly, about two months in arrears. We refresh the rates used across the site and in the rates-by-state guide when a new table is released, and each guide shows its last-updated date under the title.
Can I use these figures for a country other than the United States?
The formulas are universal, but the default rates and the 120 V assumption are US-specific. Type your own rate per kWh into the calculator and the results will be correct for any country. For appliances that list amps, multiply by 230 instead of 120 in most of Europe, Asia and Australia.
Do I need to read the guides to use the calculator?
No. The calculator works on its own with realistic defaults. The guides are for when a number surprises you and you want to know why, or when you want to find your exact rate rather than the state average.