Estimate energy with watts ÷ 1,000 × hours, then multiply kWh by an appropriate electricity rate. For a better estimate, measure total kWh over several ordinary days, including cycling and standby. A hypothetical 300W draw for eight hours daily uses 72kWh in 30 days; at an illustrative RM0.50/kWh, that is RM36. This is not a current tariff quotation or a promised running cost.
Read the power figure before doing the sums
Look for electrical input power in watts (W) in the exact model’s specifications. Do not use the water-removal capacity in litres per day, or the tank size in litres: neither tells you the electrical draw.
Check whether the wattage is rated, maximum or specified at particular temperature and humidity conditions. Treat it as a starting assumption, not a measurement of your room. A display showing instantaneous watts also tells you only what the appliance is drawing at that moment.
Energy accumulates over time and is recorded in kilowatt-hours (kWh). A steady 300W draw for one hour uses 0.3kWh. The same draw for eight hours uses 2.4kWh. If the draw changes, the total depends on how long the appliance spends at each power level.
A simple estimate, with its assumptions visible
For a first estimate, use:
Monthly kWh = watts ÷ 1,000 × hours per day × days
Estimated energy cost = monthly kWh × assumed RM per kWh
The following figures are invented examples to show the arithmetic. They are not measured results, typical Malaysian usage or current utility rates. Both rows use a 30-day month and an illustrative RM0.50/kWh.
| Example basis | Daily energy | 30-day energy | Cost at RM0.50/kWh |
|---|---|---|---|
| Assume 300W continuously for 8 hours; zero use outside that period | 2.4kWh | 72kWh | RM36.00 |
| Suppose a meter records 9.1kWh over 7 complete days | 1.3kWh average | 39kWh projected | RM19.50 |
The second row is a separate hypothetical scenario, not evidence of savings from the first. A wetter room, longer schedule or different machine could produce a higher result. Replace the assumptions with your own figures.
Allow for cycling, fan operation and standby
A humidistat-controlled dehumidifier can stop removing moisture once its target is reached and restart when needed. The fan’s behaviour between cycles depends on the model. Being switched on for eight hours therefore does not necessarily mean eight hours at the rated input.
Conversely, do not count only the hours when the compressor sounds active. Fan operation, controls and standby may still use electricity. If you build a calculation from separate operating modes, add the energy for every mode over the full period.
For a household estimate, recording total kWh is often easier than trying to guess how many minutes the compressor runs. Keep the machine in its normal routine during the measurement, including the hours it remains plugged in but idle.
Measure an ordinary week
If the appliance and meter instructions allow it, use a suitable plug-in energy meter rated for the electrical load and motor starting current. Check the connection and earthing requirements, and keep the meter and socket away from water. Do not use an improvised adaptor arrangement to make incompatible equipment fit.
Record the starting kWh reading and time, then the finishing reading after seven complete days. Subtract the start from the finish and divide by seven to get average daily kWh. Multiply by the number of days you want to budget for.
Keep a short note of the room, humidity setting, operating schedule and laundry days. Note any full-tank shutoff too: a low consumption figure is less useful if the machine stopped early and the room stayed damp. See the humidity measurement guide for a consistent way to record room conditions.
Repeat the check if the routine changes substantially. One rainy week should not be presented as an exact prediction for every month of the year.
Choose a rate that matches your electricity account
The RM0.50/kWh used above is just a calculation example. Malaysia does not have one all-in household rate that can be applied to every appliance and account. Use the current tariff for your supplier and account type.
For Peninsular Malaysia, the Energy Commission describes a base tariff and Automatic Fuel Adjustment, with AFA reflecting monthly changes. The energy charge alone is not necessarily the full change in the amount payable. Applicable bill components, incentives and taxes can affect the result.
For a closer estimate of the added bill, compare the supplier’s full-bill calculation at your usual household consumption with the same calculation after adding the dehumidifier’s estimated kWh. Keep the billing period and other assumptions the same. A bill total divided by total kWh gives a rough historical average, not necessarily the price of the next kWh.
If your account uses time-of-use pricing, split the appliance’s energy between the relevant periods. Our TNB time-of-use guide explains that account-level decision. Do not apply TNB’s schedule to Sabah Electricity or Sarawak Energy accounts.
Compare the work done, not only the watts
A lower-wattage appliance is not automatically cheaper for the same moisture-control task if it must run longer. ENERGY STAR uses integrated energy factor, expressed in litres of water removed per kWh, to describe dehumidifier efficiency under its test procedure.
When comparing specifications, check that the test conditions and measurement method match. A laboratory efficiency figure is useful context, but it does not replace a measurement in your home. Compare whether the machines achieve a similar room condition, not simply whether one draws fewer watts.
For capacity and drainage choices, use the dehumidifier buying guide. If you already have air conditioning, the dry-mode comparison helps you decide which approach fits the room before buying another appliance.
Reduce unnecessary work and check the result
Follow the manufacturer’s placement and cleaning instructions, keep air openings clear, and deal with leaks rather than asking the machine to compensate indefinitely. Avoid leaving external windows open while trying to dehumidify the room, while maintaining any ventilation needed for safe occupancy.
Try one reasonable change at a time, such as improving the drying-laundry routine or changing the operating schedule. Compare energy use alongside room comfort and humidity over similar days. The useful outcome is an acceptable room condition at a known cost—not the lowest meter reading regardless of the result.
Frequently asked questions
Does a 300W dehumidifier use 300W all day?
Not necessarily. The stated figure may describe rated operation under particular conditions. Cycling, fan-only operation, standby and changing room conditions affect the total. Measure kWh over the whole period to understand your actual use.
Does the estimate include buying and maintaining the appliance?
No. The worksheet estimates electricity only. Keep purchase price, servicing and any model-specific replacement parts separate when comparing total ownership costs.
Sources and further reading
Sources checked on 11 October 2026.
- ENERGY STAR: dehumidifiers, humidistats and efficiency
- ENERGY STAR: dehumidifier testing and capacity
- Energy Commission: electricity tariff components and AFA
