Enrichment · Passion Projects · Energy

The space heater
costs more than
everything else together.

List your appliances with their watts and how long they run, and type your electricity price. The estimator gives each one's kilowatt-hours and cost a year and shows which matters most.

Estimate the costWhat you get

The appliance energy estimator

The worked example is a made-up dorm room at an example price of $0.17 per kWh. Nothing you type leaves this browser.

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What you get

Enrichment · Passion ProjectsFree

What you finish with
Each appliance's kWh and cost a year and its share, and the total a month and a year. It prints as a summary and downloads as a spreadsheet.
Who it is for
Students in a first dorm or apartment, families looking at their bill, and environmental science or physics classes.
Format
Browser calculator for a phone, tablet or computer, by touch or keyboard. Up to 40 appliances. Prints a summary; downloads a spreadsheet (.csv); export and import a file.
Access
Free. No account, no sign-in and nothing to install. Everything you type stays in this browser; nothing is sent to Caveat.
Where it lives
The Passion Projects space in Caveat Enrichment.
Support
Questions, a correction or a request: team@caveatacademic.com.

How to use it

  1. Type the price per kWh from your bill.
  2. Add each appliance with its watts, hours a day and days a week.
  3. Read the yearly cost and the biggest user.
  4. Try fewer hours on the biggest one.
  5. Print the summary to share with roommates or family.

Estimate the cost

How the cost is worked out

Watts, hours, then the bill's unit.

The worked example: the space heaterSpace heater1,500 W2 h a day, 5 days a weekkWh a year7801,500 × 2 × 5 × 52 ÷ 1,000× $0.17$132.60a yearShare63%of the room's electricityThe worked example: the space heaterSpace heater1,500 W2 h a day, 5 days a weekkWh a year7801,500 × 2 × 5 × 52 ÷ 1,000× $0.17$132.60a yearShare63%of the room's electricity
Watts measure how fast an appliance uses energy; hours turn that into kilowatt-hours, which is what the bill charges for.

The arithmetic

Energy in kilowatt-hours is power in watts × hours ÷ 1,000. Over a year that is watts × hours a day × days a week × 52 ÷ 1,000. Cost is kWh × the price per kWh. An all-in price, total charges ÷ kWh on a bill, includes delivery and taxes.

Better numbers

A label's watts are a maximum; many devices use less, and appliances with thermostats (fridges, heaters) cycle on and off. A plug-in watt meter measures real use, including standby. ENERGY STAR and EnergyGuide labels give yearly kWh for many appliances.

Sources

  1. U.S. Department of Energy. Estimating appliance and home electronic energy use (energy.gov/energysaver).
  2. U.S. Energy Information Administration. Electric Power Monthly: average retail price of electricity to residential customers (eia.gov).
  3. U.S. Environmental Protection Agency and Department of Energy. ENERGY STAR product specifications and yearly energy use (energystar.gov).
  4. Federal Trade Commission. EnergyGuide labels, 16 CFR part 305 (ftc.gov).

The worked example is made up and its price is an example. Your figures stay in this browser. Support: team@caveatacademic.com.