Is it worth using the dry mode on your heat pump?

How much moisture do heat pumps remove?

Manufacturers don’t tend to publicise their dehumidification rates. That makes it tough to compare brands and models if you fancy a heat pump with this feature. There are a few exceptions, but where manufacturers do print the figures, they’ll be in litres per hour and buried at the back of the brochure.

As a rule of thumb, the moisture removal rate is linked to heat pump capacity and increases with heat output. For a heat pump designed for a living room – between 5kW and 8kW – you can hope for 3–5L/hour of moisture removal, at best.

How dry mode works

You may have noticed a puddle of water outside when your heat pump is operating in cooling mode. That’s dew, which forms on the cold coils of your indoor unit and is then drained away outside. Dry mode works in the same way. It won’t have the same cooling effect on the room though, as in dry mode the fan is usually down low (or it chops and changes to maintain your set temperature).

Be wary of using the function on colder evenings. Your pump can’t heat and dehumidify at the same time, so you might begin to feel the chill.

What’s the best way to use dry mode?

If your living area has moisture issues, you might want to give dry mode a go to see if it has an impact – it could be a difference maker in a room with a damp problem.

However, if you already own a dehumidifier, using it in tandem with the heat pump (set on heating mode) will bring the best results. Dedicated dehumidifiers don’t chop and change between heating and cooling to maintain the temperature in the room; they just chug away at their primary function. And refrigerant dehumidifiers are relatively energy efficient, with nowhere near the same power draw as a big heat pump – to top it off, they function better as the air temperature increases.

The obvious catch is that the dry function will impact the room that the heat pump is in, but it won’t help with the damp spare room at the back of the house. Dehumidifiers, on the other hand, can be wheeled or carried to where they’re needed. Also, for the most part, there’s no need to dry out a living area, as it tends to be the warmest, driest part of the home.

There is one obvious upside to using your heat pump in dry mode though. You never have to remember to empty a dehumidifier tank!