Estimate appliance kWh and cost by day, week, average month, current calendar month, and year, with an optional regional CO₂ factor.
A quick decision brief for this specific tool
Appliance wattage, hours per day, electricity rate, and an optional user-supplied regional or utility emissions factor
Daily/weekly/yearly usage and cost, annual÷12 average month, exact current-calendar-month total, optional CO₂, and same-hours appliance comparisons
kWh = watts × hours ÷ 1,000; annual uses 365 days, average month divides annual by 12, and the current month uses its actual day count
Choose your path
Estimate constant-rate appliance energy cost with distinct annual-average and current-calendar months, plus optional rather than invented electricity emissions.
Estimate an appliance’s bill contribution from realistic power and runtime.
Enter watts, hours/day, and marginal $/kWh; inspect daily through annual results.
Can reproduce kWh and cost and knows tiered/time-of-use/fixed charges are outside the model.
Avoid a hidden 30-day month assumption.
Compare annual÷12 average month with the current calendar month.
For 300W×8h at $0.15, sees $10.95 average month and $11.16 for August’s 31 days.
Estimate operating CO₂ only from a relevant factor.
Leave the factor blank for cost-only or enter a utility/regional lb/kWh value.
No universal factor is invented, and appliance comparisons are labeled as same-hours scenarios rather than typical usage.
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Power is converted from watts to kilowatts, multiplied by daily runtime, then multiplied by the entered energy rate.
Daily cost = watts × hours/day ÷ 1,000 × rate/kWhAnnual cost uses 365 days. Average month divides annual cost by 12; the calendar view uses the actual number of days in the current month.
Annual CO₂ is shown only when a non-negative lb/kWh factor is entered. The constant-rate model excludes taxes, tiers, time-of-use schedules, and demand charges.
Updated: July 2026
A homeowner combines measured wattage, realistic daily hours, and the marginal bill rate to estimate one appliance's annual contribution.
A student compares several nominal wattages at the same daily runtime while keeping clear that this is not typical usage.
A user enters a utility or regional emissions factor to estimate annual operating CO₂ without treating a national average as universal.
Model an appliance from watts, daily runtime, and your electricity rate. Compare annual÷12 average-month cost with the actual length of the displayed month, and add an emissions factor only when you have a relevant utility or regional value.