What Your Appliances Actually Cost to Run
Electricity bills arrive as one big number, but every device in your home is contributing in its own small way. Some appliances cost almost nothing to run — an LED bulb left on for an entire month adds maybe a dollar to the bill. Others cost more than people expect — a single hour of clothes dryer use can match a full day of refrigerator energy. Understanding which devices are the heavy hitters helps you make decisions about what is worth changing and what is fine to leave alone. This calculator works out the cost in three easy inputs: wattage, hours of daily use, and your electricity rate.
Finding the Wattage
Almost every appliance has a label, sticker, or printed nameplate with its power rating in watts. Look on the back, the bottom, the inside of the door, or the underside of the device. If the label only gives volts and amps, multiply them: a 120 V appliance drawing 8 A is rated at 960 W. The number on the label is the maximum draw — the actual power use can be lower if the appliance has a thermostat (refrigerators, freezers, ovens, water heaters all cycle on and off). For these the calculation overestimates somewhat, which is fine for planning purposes since the worst case is the more useful number to know.
Daily Hours of Use
Be honest about how many hours per day a device is actually on. A television "always on" for background noise might be on 8 hours a day even though no one is paying attention to it most of that time. A laptop in the office is plugged in for 8 to 10 hours but typically draws less when idle. Lighting in unused rooms, computers left on overnight, and standby devices add up over the course of a year. The annual cost projection at the top of this page makes it easy to see whether a small daily change is worth the effort.
Your Electricity Rate
The rate per kilowatt-hour shows up on your electricity bill. In the United States the average is around 17 cents per kWh, with wide variation between states (Hawaii is over 40, parts of the Pacific Northwest are under 12). UK rates have climbed to 25-35 pence per kWh in recent years. European rates vary widely by country. If you are on a time-of-use plan, your rate can vary by hour of day — for those plans, use the average of your peak and off-peak rates, or run the calculation twice to compare appliances that you can shift to off-peak.
The Real Energy Hogs
The appliances most worth focusing on are the ones that combine high wattage with long use: heating, cooling, and water heating. A central heating system, an air conditioner running through summer, and an electric water heater each typically account for hundreds of dollars per year. After those, big appliances that get used daily — clothes dryer, oven, dishwasher — are next. Refrigerators and freezers run continuously but draw less per hour, so they end up moderate. Lighting, electronics, and chargers are usually small individual contributors but can matter if you have many of them.
Standby Power
Devices that are plugged in but not active still draw a small amount of power — historically called vampire power or phantom load. Modern devices are far better than they used to be (energy regulations now cap most standby modes at 0.5 W or less), but older equipment can still draw 5 to 15 W per device 24 hours a day. Add up a dozen always-on devices in a home and the total can run to 50-100 kWh per year, or roughly $10-20. The biggest standby offenders today are typically older cable boxes, gaming consoles in instant-on mode, and home theater receivers.
Frequently Asked Questions
My appliance is rated in BTU, not watts. How do I convert?
For air conditioners, divide BTU/hour by the unit's EER (energy efficiency ratio) to get the wattage. A 10,000 BTU AC with an EER of 11 draws roughly 910 W. If you don't know the EER, an EER of 10 is a reasonable default for older window units.
How accurate is this estimate?
For continuously running devices the estimate is very close. For thermostatically controlled appliances (fridges, freezers, water heaters) it is a worst case — actual use is typically 30-50% lower because the device is not running every minute it is plugged in.
Should I unplug devices I'm not using?
For most modern devices, no — the standby load is too small to matter. The exceptions are older entertainment equipment, instant-on game consoles, and any device that is hot to the touch when off (heat means power use). A smart power strip can handle this automatically for clusters of devices.
This calculator runs entirely in your browser and never sends your data anywhere. Use it to compare appliances, justify upgrades, or just understand where your bill is going.
Try also: Fuel Cost Calculator · Savings Interest Calculator