Compare the loads you actually use
A short-use appliance can draw more watts yet use less monthly energy than a small device that stays on. Build the list around a question: the devices in your home office, the appliances used during a damp month, or the extra loads you are considering. The table lets you compare them on the same rate without treating every device as a continuous load.
Choose a lookup entry to fill its name and wattage. The hours and days remain yours to set. Add another row for a different appliance or operating mode. You can rename rows to distinguish two similar devices. Remove a row to exclude it from the total; adding an unfinished row hides the total until its values are valid.
The lookup is a starting point. A generic refrigerator/freezer entry cannot represent every size, age or defrost system. If a model-specific energy label or a compatible meter gives you better evidence, use that instead. Electrical input watts belong in this calculation; microwave cooking output, cooling capacity and heating output do not.
How duty cycle changes a row
Duty cycle is the fraction of the scheduled time during which a load draws the entered on-cycle power. For example, a load observed running for half of a monitoring period has a 50% duty cycle. This simple model assumes no additional off-cycle power. A compressor, fan and defrost heater with different schedules will not be described perfectly by one percentage.
Monthly kWh = watts ÷ 1,000 × hours/day × days/month × duty % ÷ 100
Monthly cost = monthly kWh × rate per kWh
Combined cost = sum of all row costs
Choose one approach. With on-cycle watts, enter the full observation window and the observed duty cycle. With average watts measured across that window, enter the same hours and leave duty at 100%. If you already shortened the hours to count only running time, leave duty at 100% too. Reducing both would undercount consumption.
The lookup source calls its values estimated average watts and does not establish a measured compressor-on rating. Selecting a preset therefore restores duty to 100%. Replace its wattage with verified on-cycle power before applying a separate cycling adjustment.
Worked monthly comparison
These are chosen planning schedules using the utility lookup's 1,500 W heater and 100 W laptop references. They are not measured household usage. The heater runs 3 hours daily and the laptop 8 hours daily, each for 30 days at 100% duty.
| Appliance | kWh/month | Cost/month |
|---|---|---|
| Heater | 135 | $24.76 |
| Laptop | 24 | $4.40 |
| Total | 159 | $29.16 |
The heater calculation is 1.5 × 3 × 30 = 135 kWh. The laptop calculation is 0.1 × 8 × 30 = 24 kWh. Together they use 159 kWh in this scenario, costing $29.16. The total uses unrounded row values, so displayed rounded rows can occasionally differ from the total by a cent.
Changing an assumption changes the estimate, not the appliance. A different duty cycle does not promise a saving. Seasonal equipment also needs a seasonal schedule; multiplying a busy month by 12 can overstate a year.
Assumptions and limits
- Each row uses one power value and one monthly schedule. Duty cycle scales that scheduled time.
- Presets are the source utility's rough average-wattage references. They are not product specifications, measured household averages, or verified on-cycle power. They start at 100% duty.
- For measured average watts, leave duty at 100%. For measured on-cycle watts, set duty to the share of scheduled time that the load runs. Do not reduce both hours and duty for the same off time.
- All appliances share the entered rate and currency. The starting USD rate is an EIA national reference; use your tariff's applicable variable charges for a closer estimate.
- Annual cost repeats the entered month 12 times. Fixed charges, separate tax calculations, and unlisted loads are excluded.
Use the appliance measurement guide to choose a wattage basis. For separate peak and off-peak rates, calculate each period independently using the Electricity Cost Calculator; this inventory shares one rate across every row. The tariff guide explains how to choose that rate.
Appliance inventory questions
It offers 28 rough references from Willmar Municipal Utilities, not ratings for your model. Check a product's electrical input specification or a compatible energy meter. Size, age and operating mode can change the power substantially.
Sources and review
- Willmar Municipal Utilities: appliance usage guide: all lookup wattages, described by the source as estimated averages.
- EIA table 5.6.A: June 2026 US residential rate.
- EIA: measuring electricity: power and energy units.
- FTC: using EnergyGuide labels: standardized estimates and local usage.
Reviewed September 7, 2026. Read the estimate disclaimer. Follow product instructions for measurement equipment and ask a licensed electrician about hardwired loads or electrical safety.