Usually yes. A typical dehumidifier draws around 300W against 2,000W for an electric heater, and drying the air makes a room feel warmer at the same temperature.
- A 300W dehumidifier run eight hours costs roughly 63p a day at the current cap rate.
- A 2kW electric heater run for three hours costs about £1.57.
- The dehumidifier also removes the water rather than just warming it, which is the actual problem in a condensation-affected room.
- Compressor models are cheaper to run in a warm house; desiccant models work better in a cold one, such as a garage or a conservatory.
Use the running cost calculator with your own rate and your own model's wattage, which is on the plate on the back.
A dehumidifier treats the symptom. If the water is coming in through the wall it will run permanently and you will pay for it permanently.
Removing a litre of water from the air takes far less energy than raising the temperature of a whole room by several degrees, and dry air at 18C feels warmer than damp air at 20C.
Household chemicals can be dangerous in combination. Never mix them, keep the room ventilated, and test anything on a hidden patch first. Full disclaimer.