Is a dehumidifier worth it?
When a dehumidifier genuinely helps, which type suits a cold house, and what it costs to run against what it saves.
- Difficulty
- beginner
- Time
- 20 min
- Read
- 2 min
Short answer
Worth it for condensation, drying washing indoors and persistently damp rooms — not as a fix for a leak or rising damp. In an unheated or cold room, choose a desiccant model; compressor types lose most of their effectiveness below about 15°C.
A dehumidifier removes water from the air. That helps enormously with condensation, which is water the air is carrying, and not at all with water arriving through a wall. Matching the machine to the problem is most of the decision.
Step by step
- Confirm you have a condensation problem.Wet windows, damp on cold outside walls, mould in corners, washing taking days to dry. Damp that is worse after rain, or rising from the floor, is a different problem.
- Choose the type for the temperature.Compressor models are cheaper to run in warm rooms but drop off sharply in the cold. Desiccant models work well in cold rooms and add a little warmth, at higher power consumption.
- Size it to the space.Rated in litres per day. A small flat needs far less than a whole cold house. Oversizing wastes money; undersizing means it runs constantly without ever winning.
- Use a humidistat rather than running it constantly.Set a target of around 50% relative humidity and let it cycle. Running continuously costs money and over-dries the air.
- Position it centrally with clear airflow.Not jammed against a wall or behind furniture. It needs to circulate the room's air, not the pocket of air around itself.
- Use laundry mode for drying washing.This is where a dehumidifier is most clearly cost-effective — it is usually cheaper than a tumble dryer and it stops the moisture ending up on your walls.
- Keep ventilating anyway.A dehumidifier is not a substitute for fresh air. It manages moisture; ventilation deals with everything else in the air.
Tips
- Empty the tank or fit a continuous drain hose. A full tank stops the machine, usually overnight, and you lose a night's work.
- Clean the filter regularly. A blocked filter cuts effectiveness substantially and increases running cost.
- If you are running it to dry washing, doing it in one closed room is far more effective than spreading washing through the house.
Common mistakes
- Buying one to fix rising or penetrating damp — It removes moisture from the air, not from a wall that water is arriving through. The damp will simply continue.
- Choosing a compressor model for a cold garage or bedroom — Below about 15°C they become markedly less effective, and in a cold room they can ice up.
Questions people ask
Are dehumidifiers expensive to run?
Modest for a compressor model in a warm room; more for a desiccant. Set against a tumble dryer for drying washing, they usually compare well.
What humidity should I aim for?
Around 50% relative humidity is a common target. Sustained above about 60% is the range where mould becomes likely.