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To estimate an electric appliance’s running cost, multiply the electricity it uses in kilowatt-hours (kWh) by your applicable price per kWh. If you know only its wattage and how long it runs, calculate kWh as watts × hours ÷ 1,000, then multiply by your rate. The result is an estimate: the appliance’s actual behavior, your schedule, and your utility’s pricing determine what it adds to your bill.
The basic formula for appliance running cost
Electric utilities bill energy in kilowatt-hours, not watts. A kilowatt-hour is the amount of energy used by a 1,000-watt appliance running for one hour. The U.S. Department of Energy (DOE) uses kWh to describe electricity use; the calculation below turns that energy use into a cost using your own electricity price.
Running cost = energy used in kWh × electricity price per kWh.
For example, if a cycle uses 1 kWh and your applicable rate is 20 cents per kWh, the energy cost for that cycle is 20 cents. That rate is an example for explaining the arithmetic, not a current national price. Your own rate may be different, and it can vary by time or usage tier.
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- Various Monitoring Parameters: The power meter plug can monitor the power (W), energy (kWh), volts, amps, hertz, power factor, cost, minimum and maximum power (W), cumulative days and time of your appliances. By switching 7 display modes, you can easily know the various parameters while the appliance is working. The home energy monitor can also calculate and display how much power your appliance uses and how much electricity bill it cost in cumulative time
- Upgraded LCD Display: With large screen size 2.36 inch x 1.85 inch, clearer monitor backlit, our electrical usage monitor can display the data clearer and more visible no matter day or night. 180°full wide viewing angles is great for reading and recording the data in any angles. No need to stand on the front of the display and bend over to read the numbers
- Adjustable Backlight Time: Our upgraded watt meter has 5 options of backlight time. The default backlight time duration is 10 minutes(bL-0). If you want to change the backlight time, you can press and hold "UP" and "DOWN" button at the same time to enter backlight time setting, then press "UP" and "DOWN" to select the backlight time (bL-0 =10 minutes, bL-1=1 hour, bL-2=4 hours, bL-3=8 hours, bL-4=always on), finally press the "COST" to save the backlight time settings
- Overload protection: When the power of the appliance exceeds the overload power, the LCD will display “OVERLOAD” to warn the user. All the buttons will quit working and can only be workable when you lower or remove the load power. The default overload power is 3680W and is adjustable from 0 to 3680W. In general, you need to set the overload power to 1800W before using. Just press the "function" button for more than 3 seconds to enter the setting
- Data Memory Function: The wattage meter will record your power consumption data when you remove it from socket, or remove appliances from the electricity monitor. You can directly see the last data when you use it next time. This function can also automatically save the data when there is a sudden power failure
Calculate energy from watts and hours
If an appliance’s label or manual gives watts but not kWh, use:
Watts × hours used ÷ 1,000 = kWh
Then multiply the kWh result by your per-kWh price. For instance, using the same illustrative 20-cent rate, a 500-watt appliance running for two hours uses 1 kWh (500 × 2 ÷ 1,000) and costs 20 cents for that period. This is a direct calculation from the stated wattage and runtime; it does not mean the appliance necessarily draws that wattage continuously.
Choose the period you want to estimate
- One cycle: kWh per cycle × your rate per kWh.
- One year from a label: annual kWh × your rate per kWh.
- A repeated schedule: energy per use × number of uses in the period × your rate, provided you have a reasonable energy estimate for each use.
Label the result as per cycle, month, or year. A number without a time period is hard to interpret and can be misleading when comparing appliances with different schedules.
Find the appliance’s energy use
Use the EnergyGuide estimate when available
An EnergyGuide label is a useful starting point for comparing similar models. DOE’s Guide to Kitchen Appliances explains that the label provides model energy-use information and an estimated annual operating cost. The estimate is based on assumptions, however; your local rate and the way you use the appliance can change your actual expense. Recalculate annual cost using the annual kWh and your own electricity rate when that figure is available.
If the label gives an annual operating-cost figure but not the assumptions behind it, treat the dollar amount as a comparison aid rather than a prediction of your bill. The underlying energy-use figure is more useful for adapting the estimate to your tariff.
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- Multi-function power monitor: Our electric usage monitor can monitor the power (W), electricity(kWh), voltage(V), frequency(Hz), current(A), power factor(PF), unit price($/kWh), total cost($) of your appliances. By switching 8 display modes, you can easily know the various parameters while the appliance is working. The “electricity” mode can calculate and display how much power your appliance uses. And the “total cost” mode will show how much electricity bill it cost in cumulative time
- Overload protection: When the loading power of the appliance is over the default overload threshold 1800W, the whole display with backlight and the word “OVERLOAD” will keep flashing to warn the users. Please turn off the appliance for safety concern
- Premium Material: The whole body of our energy meter is made of high-quality ABS material. It makes our home electricity usage monitor more long lasting, fireproof and anti-drop. The standard US socket and plug is suitable for all US standard appliances
- Backlight Display: With white backlight and black words, the LCD display of our home power monitor can display the data clearer and help you to read the data easier no matter day or night. The backlight will only lights up when the device is connected to AC power. If no button is pressed, the backlight turns off automatically after 10 minutes. You can also press the "UP" button to turn off the backlight manually, and press any button to turn on backlight again
- Easy to reset: No reset tool needed, our appliance power usage meter is easy to reset. You can press the “M” button for 5 seconds directly to reset the device. After reset, all cumulative data (electricity quantity, cost) will be cleared, and all settings will be restored to factory settings
Use the appliance’s real schedule, not just its rated power
Watts multiplied by hours is an estimate when the appliance’s draw stays close to the wattage used in the calculation. Many appliances do not run at one steady power level throughout their operation: they cycle, pause, heat, cool, or change speed. A refrigerator, for example, does not operate like a device that draws its full rated wattage without interruption all day. For appliances with cycles or changing loads, an annual kWh label or an appropriate energy measurement can better represent actual use than multiplying maximum or nameplate watts by every hour in the calendar.
Use energy per cycle for appliances that have a meaningful cycle measure, and annual kWh for appliances whose use is better described over the year. If you estimate from wattage, write down the assumed active hours and frequency so you can revise the calculation if your schedule changes.
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A plug-in electricity usage monitor, sometimes called a watt meter, can help measure kWh for a compatible appliance. Check that the monitor’s voltage and current ratings suit the appliance before using it. This approach is only for appliances that can safely be connected through that instrument; it is not a recommendation to meter hardwired equipment or high-load appliances with an unsuitable device. The monitor’s reading covers the period measured, so use a representative span that includes the appliance’s normal operation rather than assuming a brief sample describes a full year.
Use the rate that applies to the appliance’s usage
Check your electricity bill or utility plan for the per-kWh price that applies where and when the appliance runs. A bill’s total charges divided by total kWh can provide a rough blended rate, but that average may include fixed monthly charges that do not change when one appliance uses less electricity. For estimating the cost of operating one appliance, use a variable energy rate where possible rather than assigning it a share of fixed fees.
Some plans use time-of-use prices, which change with the time of day; others use tiers, where the price changes after consumption passes a threshold. In those cases, one flat rate may be only an approximation. If the appliance can be scheduled, estimate its use using the price for the hours it is likely to run. If using a tiered plan, consider whether the appliance’s energy falls into a different price tier over the billing period.
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Delivery charges, taxes, and other variable fees can also make the final bill differ from an energy-only calculation. Keep the estimate’s scope clear: it may be the cost of the electricity itself, not every charge that appears on the bill. Do not attribute a fixed monthly fee to a single appliance as though switching that appliance off would eliminate the fee.
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The following federal examples demonstrate how assumptions affect estimated running costs. They are not universal household prices, current offers, or predictions for every home. The appliance types, test methods, operating assumptions, and assumed electricity prices matter.
| DOE example | Energy and stated cost | Assumptions and limits |
|---|---|---|
| ENERGY STAR refrigerator | 363.5 kWh/year and $36/year | DOE Federal Energy Management Program (FEMP) product data dated December 2023. The example is an 18.1-cubic-foot top-freezer refrigerator and assumes $0.099/kWh under the stated test method. |
| ENERGY STAR dishwasher | 240 kWh/year and $24/year as reported in the example | DOE FEMP product data dated October 2023. The energy-cost estimate is described as using $0.09/kWh; the combined utility example assumes 215 cycles per year and specified federal-facility water and sewer prices. The reported energy and dollar figures do not exactly reconcile: 240 kWh × $0.09/kWh equals $21.60, not $24. Use the stated inputs to recalculate rather than treating the reported dollar figure as a universal result. |
| ENERGY STAR central air conditioner | 2,612 kWh/year and $288/year | DOE FEMP illustration for a 36,000 Btu/h unit, with specified test assumptions, efficiency, operating hours, and an assumed 11 cents/kWh. It should not be generalized to window units, other capacities, or every climate and usage pattern. |
These examples show why energy use and the price assumption should travel together. The refrigerator’s example price is tied to its stated test and rate; the air-conditioner estimate is tied to specified operating hours and capacity. Neither figure is a quote for a reader’s home.
DOE’s Electricity 101 page reports that a typical U.S. household uses 920 kWh per month and that appliances account for 64.7% of consumption. Those are broad household-context figures, not the cost to run a particular appliance or a dated 2026 benchmark. Household usage varies, so neither statistic can substitute for a model-specific estimate and the reader’s rate.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Include water and purchase price when comparing appliances
Electricity is not the only operating cost for every household appliance. A dishwasher also uses water, and the associated water and sewer charges matter where they are material. If the home heats water electrically, some of the water-heating energy may also affect the electricity bill. DOE FEMP’s dishwasher example combines energy and water assumptions, illustrating why an electricity-only total may not capture the full utility cost.
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- Various Monitoring Parameters: The power energy meter can monitor the power (W), energy (kWh), volts, amps, hertz, power factor, cost, minimum and maximum power (W), cumulative days and time of your appliances. By switching 7 display modes, you can easily know the various parameters while the appliance is working. The home energy monitor can also calculate and display how much power your appliance uses and how much electricity bill it cost in cumulative time
- Upgraded LCD Display: With large screen size 2.36 inch x 1.85 inch, clearer monitor backlit, our electrical usage monitor can display the data clearer and more visible no matter day or night. 180°full wide viewing angles is great for reading and recording the data in any angles. No need to stand on the front of the display and bend over to read the numbers
- Adjustable Backlight Time: Our upgraded watt meter has 5 options of backlight time. The default backlight time duration is 10 minutes(bL-0). If you want to change the backlight time, you can press and hold "UP" and "DOWN" button at the same time to enter backlight time setting, then press "UP" and "DOWN" to select the backlight time (bL-0 =10 minutes, bL-1=1 hour, bL-2=4 hours, bL-3=8 hours, bL-4=always on), finally press the "COST" to save the backlight time settings
- Overload Protection: When the power of the appliance exceeds the overload power, the LCD will display “OVERLOAD” to warn the user. All the buttons will quit working and can only be workable when you lower or remove the load power. The default overload power is 3680W and is adjustable from 0 to 3680W. In general, you need to set the overload power to 1800W before using. Just press the "function" button for more than 3 seconds to enter the setting
- Data Memory Function: The wattage meter will record your power consumption data when you remove it from socket, or remove appliances from the electricity monitor. You can directly see the last data when you use it next time. This function can also automatically save the data when there is a sudden power failure
DOE’s kitchen guide puts the comparison succinctly: “Every appliance has two price tags: what you pay to purchase it, and what you pay for the energy and water it uses.” For a replacement decision, compare both the upfront price and expected operating expenses. Older example savings in a guide should not be treated as current product offers or guaranteed savings in your home.
Compare like with like
- Compare annual kWh and recalculate annual energy cost at your rate.
- Match capacity and expected workload; two models with different capacity or usage assumptions are not a fair direct comparison.
- Check whether the figures use comparable test methods and schedules.
- For dishwashers, include water use per cycle and the local water and sewer price if you want a fuller utility comparison.
- Include purchase price when deciding whether the lower-running-cost model is worth its additional upfront cost.
A more efficient model can cost less to operate and still fail to pay back its higher purchase price during the time you own it. Compare the added upfront cost with the expected energy and water savings over your planned ownership period. DOE FEMP describes lifecycle cost-effectiveness in terms of discounted lifetime savings compared with the additional upfront cost; the result depends on the time period and assumptions, not just which model has the lower annual kWh.
Estimate an existing refrigerator or freezer carefully
For some U.S. consumer refrigerator and freezer models, DOE offers an online energy-rating lookup based on model and year, with seal condition included in the lookup. The tool’s page, published November 10, 2023, says its model coverage is incomplete and includes units above 10 cubic feet. Its result is a model estimate, not a meter reading or a lookup of your electricity rate. If your model is absent, that does not establish its actual consumption; use a suitable measurement or another model-specific energy source rather than treating the missing result as zero.
Common calculation mistakes to avoid
- Confusing watts with kWh: watts describe power; kWh describe energy over time. Convert before multiplying by a per-kWh price.
- Assuming rated watts are continuous draw: appliances that cycle or change output may use less than a full-power estimate suggests. Prefer kWh-per-cycle or annual-kWh data when available.
- Using a generic price as if it were yours: a national or illustrative rate cannot capture your local tariff, time-of-use period, or tier.
- Mixing time periods: a per-cycle cost cannot be compared directly with an annual figure without converting both to the same usage period.
- Counting fixed charges as avoidable appliance costs: a fixed bill charge generally remains even if an appliance is not used.
- Ignoring non-electric utilities: for a dishwasher, a full comparison may also require water and sewer costs.
- Treating a label estimate as a bill guarantee: actual runtime, household habits, rates, and extra charges can all change the result.
For the clearest estimate, keep the energy figure, rate, time period, and usage assumptions together. If one of those inputs is uncertain, state that uncertainty in the result rather than presenting a precise-looking dollar amount as an exact bill prediction.
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