The 500 W rating and eight-hour schedule are scenario inputs. They are not a claim about a standard unit. Use the rated input from your model or a measured average. A compressor may cycle while the control remains set to run continuously.
What IEF measures
ENERGY STAR's dehumidifier criteria define Integrated Energy Factor in litres of water removed per kWh, including dehumidification and standby or off modes under representative test conditions. Its testing page explains that the post-2019 procedure includes off-cycle energy and tests portable units at 65°F.
IEF answers an efficiency question: how much water was removed per unit of energy in the test. It does not state your room's humidity, hours, target setting, filter condition or local price. Those inputs control cost.
Use watts for a running-cost estimate
For a rated-input estimate, use:
Monthly kWh = watts ÷ 1,000 × active hours per day × active days per month × duty cycle ÷ 100.
The worked scenario is 500 ÷ 1,000 × 8 × 30 × 100 ÷ 100 = 120 kWh. At $0.1834/kWh, 120 × 0.1834 = $22.008, displayed as $22.01.
If a monitor records 3.2 kWh over 24 hours, divide by one day and use 3.2 kWh/day. An annualized 30-day comparison would be 96 kWh. The measured result already includes cycling, so enter a full 24-hour period at 100% duty when converting it to an average watt value. Do not apply a second duty reduction.
Compare duty scenarios
These scenarios hold 500 W, eight scheduled hours and 30 days constant. The duty percentages are inputs for sensitivity analysis, not claims about how a particular model cycles.
| Duty input | Monthly kWh | Cost at $0.1834/kWh |
|---|---|---|
| 25% | 30 | $5.50 |
| 50% | 60 | $11.00 |
| 75% | 90 | $16.51 |
| 100% | 120 | $22.01 |
The same table can represent scheduled operation, but it cannot estimate moisture removal. A unit that runs at a lower duty may remove less water, and a unit's fan can continue while its compressor is off.
Check the room conditions
ENERGY STAR says frost can form below 65°F and cause a compressor to cycle without removing moisture. A filter or airflow restriction can also change operation. Treat these as reasons to inspect the manual and record observations, not as a fixed percentage to add to a bill.
If you need to know what happened in your room, use a suitable plug-in monitor and record the start and end kWh. Do not open the appliance or alter wiring. A whole-home installation needs a qualified professional.
Keep price and energy separate
At a chosen $0.25/kWh rate, the 120 kWh scenario costs $30.00. The energy amount is unchanged. At the EIA benchmark, a 200 kWh scenario costs $36.68. That higher cost could result from a longer schedule, a higher average input or a different duty pattern. The formula shows which input changed.
The estimate excludes fixed charges, taxes, time-of-use prices and the value of the water removed. It also does not turn IEF into an annual cost. Use the product's own rating for comparisons and your meter for your home's consumption.
Use the appliance running-cost calculator, appliance measurement guide, electricity-rate guide and EnergyGuide guide. Each result is a planning estimate for the inputs you can support.
Make the comparison repeatable
Write down the room temperature, humidity target, filter condition, start and end meter readings, and the exact dates. Those notes explain why two observations can differ without changing the arithmetic. A short observation can be useful for a check, while a longer observation captures more compressor cycling.
Compare like with like. Use the same scheduled hours, rate and number of days when comparing two scenarios. If one unit removes more water, its IEF and its operating schedule both matter; a lower electricity cost alone does not establish better moisture control. Keep the model number with the result so a future replacement is not mistaken for the tested unit.