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Dehumidifier v Tumble Dryer

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  • waqasahmed
    waqasahmed Posts: 1,984 Forumite
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    Meatballs said:
    It would be great to get a definitive answer on this one as it has come up before.  A tumble drier with a heat pump is working in a very similar way to a dehumidifier but it's all happening in a much smaller space. So in theory it should be cheaper to run? On the other hand it also move the clothes around all the time so that's more energy.   I haven't tried drying with the dehumidifier but I'm very happy with the tumble drier (especially on cold but sunny days!)  I would try a comparison test but it would be a lot of faff to do it and getting accurate electricity consumption estimates over such a long period nigh impossible. 
    There's two styles of dehumidifiers:

    * Desiccant-based which blow the air across a  chemical desiccant to absorb the water, then use heat to extract the water from the desiccant. These work well at all temperatures and they cause the room to heat up a fair amount.
    * Condensing dehumidifiers which cool some fins (same refrigerant principles as heat pump), and blow the air across this to cool it down and the moisture to condense. These are more efficient but I think they work best from about 15C upwards.

    The condensing one is the closest to the heat pump but its not doing the same action. The heat pump is taking heat from the air and putting it into the machine to cause the water to evaporate from the clothes, presumably its then doing a condensing function to collect the water too. The dehumidifier is cooling the air in the room across its condenser coils to remove the humidity and mostly letting the clothes air dry. 

    As for what's more energy efficient my condensing dehumidifier uses 185W but suspect it would need to be on for many hours to dry clothes - 10 hours would be 1.85kWh. Internet says around 2.16kWh for a load in a heat pump tumble dryer.

    I guess the other advantage is you get a warm room too
  • nonumb
    nonumb Posts: 36 Forumite
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    Hi all, 

    Piggy backing on this thread as its relevant. 

    We have an older condenser dryer that works very well but isn't the most energy efficient. It takes about 3kwh to dry a load depending on what's in there. Could be up to 4 for a large load could be as low as 2 for a small one.

    This is in a small purpose built utility room with a small pulley maid on the ceiling and a small extractor fan on the wall. It's about 7.5m3 total air volume. We have solar panels and a battery so in summer the low efficiency isn't an issue and in winter we try and shift onto the octopus go night rate. With all this taken into account the payback period for a very efficient heatpump tumble dryer over our current one is about 5 years. For a dehumidifier it seems lower. 

    We tumble dry some clothes but not all. Obviously there are some that can't be tumble dried and I'm very tall so struggle with any shrinkage on clothes. 

    When the tumble dryer is on the room gets very very humid and the clothes that are hanging up take ages to dry. Not great for jeans and things like that. However we still want a tumble dryer for the times when you just want something done quickly for when there is loads of solar so the energy is negligible. 

    Firstly would it be an issue to run the tumble dryer and dehumidifier at the same time? In my mind having the tumble dryer in a less humid room would only be a good thing. It would then allow clothes that are hung up to dry more quickly. 

    Next does anyone have any thoughts on speed? Seems like mostly people say 5-6 hours for drying clothes using a dehumidifier. Anyone tested using an air circulating fan as well? With the tumble dryer on the room seems to get into the mid-high 20s so my understanding is that this would help the dehumidifier. 

    I'm looking at a 12l dehumidifier possibly the Devola wifi one. We have drainage available to would look to put the condensate pipe into the drain to avoid having to empty the tank. 

    Anything I haven't considered?

    Any advice appreciated. Coming at this at a slightly different angle than most. If this is better suited to another thread I'll create but it seems like this may add to the discussion here. 
  • k_man
    k_man Posts: 1,636 Forumite
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    The drain pipe from most dehumidifiers is quite low, and gravity fed (not pumped), so you would need a low drain to ensure the pipe is only going down.

    Unless the dehumidifier can be located higher up of course, but that may make accessing controls harder (depending if what can actually be controlled via wifi).
  • With our (Miele) heat pump dryer, we have found that we can dry everything in it as the temperature is lower. It uses around 0.8kwh compared to 3kwh for our old condenser. The payback period is looking to be less than 3 years, as we use it for around 6 loads a week.
  • nonumb
    nonumb Posts: 36 Forumite
    Part of the Furniture 10 Posts Combo Breaker
    k_man said:
    The drain pipe from most dehumidifiers is quite low, and gravity fed (not pumped), so you would need a low drain to ensure the pipe is only going down.

    Unless the dehumidifier can be located higher up of course, but that may make accessing controls harder (depending if what can actually be controlled via wifi).
    Thanks - we'd have it on top of a surface above the washer and drier so gravity fed is no issue for us. Good point though. 
  • nonumb
    nonumb Posts: 36 Forumite
    Part of the Furniture 10 Posts Combo Breaker
    With our (Miele) heat pump dryer, we have found that we can dry everything in it as the temperature is lower. It uses around 0.8kwh compared to 3kwh for our old condenser. The payback period is looking to be less than 3 years, as we use it for around 6 loads a week.
    Fair point we could probably use it more but with the solar and battery it means our payback period is a lot higher. Certainly when the condenser dryer dies we will replace it with a heat pump one I'm just not convinced it makes sense for our usage to replace now. 
  • Fait enough. Our old dryer was still working and we got £100 for it secondhand. Other than the cost saving, I reckon we save more than an hour a week by tumble drying everything. The lower temperature and running costs really are a game changer.
  • QrizB
    QrizB Posts: 15,190 Forumite
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    nonumb said:
    We have an older condenser dryer that works very well but isn't the most energy efficient.
    When the tumble dryer is on the room gets very very humid ...
    This statement is mildly concerning.
    The condensate from a condenser dryer should go down the drain together with the cooling water. It should not be making your utility room humid. It makes me wonder if there's something wrong with your dryer.
    N. Hampshire, he/him. Octopus Intelligent Go elec & Tracker gas / Shell (now TT) BB / Lebara mobi. Ripple Kirk Hill member.
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  • nonumb
    nonumb Posts: 36 Forumite
    Part of the Furniture 10 Posts Combo Breaker
    edited 6 November 2022 at 11:01AM
    QrizB said:
    nonumb said:
    We have an older condenser dryer that works very well but isn't the most energy efficient.
    When the tumble dryer is on the room gets very very humid ...
    This statement is mildly concerning.
    The condensate from a condenser dryer should go down the drain together with the cooling water. It should not be making your utility room humid. It makes me wonder if there's something wrong with your dryer.
    Interesting. We do get a lot of water in the condensate collection tank, but the room does get more humid. I just assumed the condenser wasn't 100% efficient at removing the water from the air and because it is a very small room it was more noticeable. 
  • Spies
    Spies Posts: 2,224 Forumite
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    80% efficiency isn't unusual and as you say, small room makes it more noticable. 
    4.29kWp Solar system, 45/55 South/West split in cloudy rainy Cumbria. 
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