Hot feed for washing machine

[Russell griffiths]

Evening. 
wife is shopping for a new washing machine and I’ve noticed a couple come with hot and cold feeds. 
what’s anybody’s opinion on the hot feed models, is there a massive saving on not having to heat a cold water feed, but if it takes hot from our cylinder, then that has to be replaced, and washer running during the day with solar making electricity during the day. 
 

are we talking a couple of pennies saving rather than just a cold feed machine. 
 

confused as usual 🤯

[saveasteading]

Because its confusing. 

Solar complicates the calculation.   Without it, the tank water should be cheaper.

With it?

Will the team work to the required times?

 

Let us all know your decision, with reasoning.

[JohnMo]

Really depends on distance from cylinder. May just take in cool water so it will heat anyway and deplete the cylinder. Solar only really applicable in summer.

 

Different washers are/ can be more efficient energy wise. We just move our Bosch washer to the garage (it used loads of electricity) and moved to a Samsung it seems way better on electric. 

[DamonHD]

One huge energy saving (~80%) is to run washes as you can cold, so buy a machine that can do that.  We do everything except bedding on cold.

 

https://www.earth.org.uk/note-on-Zanussi-ZWF01483W-freestanding-washing-machine-REVIEW.html

 

Also as @JohnMo says, a water- (and thus energy-) efficient machine may not draw enough hot for it to reach the machine at all from the tank/boiler.

Edited June 22 by DamonHD

[Oz07]

I had one next to combi in last place and thought about feeding it via a blended hot. Never did in the end.  Depends how close to source or if you have a circulating hot in your place?

 

Another vote for samsung here sick of pissing around with less than 5 yr guarantee. As for washing cold that's a no call me a luddite but most gets 40c towels get 60c. 

[DamonHD]

Both circulating hot and washing unnecessarily at 40C or above are huge consumers of energy.  (And washing too hot ages clothes prematurely.)

 

That costs money and climate emissions.

 

The OP was talking about 'savings' from a dual-fill machine.  Better savings would come from NOT having circulating hot and NOT washing hotter than actually needed.

Edited June 22 by DamonHD

[SteamyTea]

It is pennies difference.

My Bosch uses between 30 litres and 110 litres, with temperatures ranging from between 30°C and 60°C.  It can also take up to 9 kg of load.

So taking the worse case, cottons at 60°C, max load of 9kg, the manual says it uses 1.75 kWh.  So even at my day rate, that is about 61p.  As I usually run it at night, it is 25p.

On the mixed load 40°C setting, which can take up to 4 kg, it uses 0.64 kWh.  So either 23p or 9p.

 

I usually use the 'speed perfect' setting at 30°C and I seem to remember that it uses 0.3 kWh.  So 11p or 4p.

 

So really, washing machines are pretty good.

 

The big saving is is not using a tumble dryer.  I am on my second Poundland washing line (I still have some left from the second one I bought), so that has cost be 10p/year.

 

 

Just thought that at about £8/m³ for water and waste, the small, 30 litre wash costs 24p.  Have I ever mentioned that we have the most expensive water in the country, which will also make it one of the most expensive in the world.

 

Edited June 22 by SteamyTea

[Mike]

3 hours ago, JohnMo said:

Really depends on distance from cylinder. May just take in cool water so it will heat anyway and deplete the cylinder.

Yes, that's essentially the reason most modern machines are cold only; they use so little water that the hot water often won't reach the machine - it will just cool down in the pipe, so it's more energy efficient to use cold.

[Nickfromwales]

If the hot water is heated by solar in summer and off peak electricity during winter, via a HP, then DHW will

cost pennies, but heating water in the machine via direct electricity will be almost 100% efficient, whereas transporting hot water across the length of the house, sporadically, will be very much less efficient; setting aside the subject of how cheap it was to actually make the hot water.

 

If you’ve a hot return then that would help obvs, but would need to be on.

 

Cold fill afaic, savings would be very little, if any, unless the machine was next to the hot water tank, as you can use the PV to heat the washing machine if it’s used 2 hours prior > 2 hours past midday eg in that ~4 hour window.

[Russell griffiths]

So get the wife to pick the machine she likes, and sod splitting hairs over a pound hear and there. 
cheers all. 

[DamonHD]

Well, get one that is water- and energy- efficient, that she likes, I suggest.  Cold only is fine.

[saveasteading]

Efficiency of stacking can delay use til the next meal. That will save more energy, and water, than anything else.

Apparently long, smart programmes are also efficient.

I don't know what is smart? Perhaps how mucky the water is.

 

If you get it fitted by the delivery guys, double check after they've gone and check for leaks. They arent employed for their plumbing skills. My last 2 have both leaked from the water connection causing great problems. In each case it was simply mis-threaded.

[SteamyTea]

1 hour ago, DamonHD said:

Well, get one that is water- and energy- efficient, that she likes, I suggest.  Cold only is fine.

Yes, I think total capacity is the important part. Less washes needed.

 

1 hour ago, saveasteading said:

don't know what is smart? Perhaps how mucky the water is.

Think it is the mass of laundry. Water needed to be replaced as the soap powder has to be washed out.

 

I recently got so decarboniser for work, it is mixed with water and you dump the blackened pots, pans and grills in it.

Looked at the chemicals in it for the COSHH file, same stuff as washing powder.

Worth knowing if you have a blackened kitchen tool.

[sharpener]

On 23/06/2025 at 09:22, saveasteading said:

If you get it fitted by the delivery guys, double check after they've gone and check for leaks. They arent employed for their plumbing skills. My last 2 have both leaked from the water connection causing great problems. In each case it was simply mis-threaded.

 

For a friend they didn't remove the blanking plug in the connection to the sink waste so the machine threw an error code and didn't work. Can't see the point of paying £25 for someone to connect 2 pipes and plug the thing in. If there is anything out of the ordinary they won't do it anyway.

 

IIRC hot and cold fill washing machines only draw from the hot on the high temperature programmes so you will not save anything on everyday washes.

[Dave Jones]

ASHP tumble dryer, expensive up front but ours very economical to run. Free in daytime virtually all year with solar.

[Nickfromwales]

3 minutes ago, Dave Jones said:

ASHP tumble dryer, expensive up front but ours very economical to run. Free in daytime virtually all year with solar.

I avoided a HP TD as all the manufacturers stated very very long drying times…..

[JohnMo]

Manufacturer drying times assume a lot, full to capacity being one, but with an efficient spin cycle dry times are ok, generally no longer than an hour generally for us, in fact no noticeable difference from our last condensing dryer 

[LnP]

Am I right in thinking that if your tumble dryer is not a heat pump one, it needs a vent to the outside? If so, is that a problem for achieving good structural leak tightness?

[JohnMo]

23 minutes ago, LnP said:

Am I right in thinking that if your tumble dryer is not a heat pump one, it needs a vent to the outside? If so, is that a problem for achieving good structural leak tightness?

No

 

Condenser dryer, collects water the same as a heat pump one does. A condenser dryer uses an electric heating element, the HP a heat pump.

 

A dryer that needs an outside vent is neither of the above, generally as old as the hills.

Edited Monday at 10:53 by JohnMo

[LnP]

1 hour ago, JohnMo said:

No

 

Condenser dryer, collects water the same as as a heat pump one. A condenser dryer uses an electric heating element, the HP a heat pump 

Interesting. I wasn't sure what would be the cold surface the moist air was condensed against. Just did some Googling and they have a heat exchanger where the hot moist air out of the dryer exchanges heat against the colder incoming air from the room. Thinking about the heat and material balance around it - since the condenser is being cooled by incoming air from the room, there must be air going back out into the room which has got to be hotter and moister than what went in. Maybe that hot air is OK in winter but not what you want in the summer if you're concerned about over heating? And once that warm moist air coming out of the dryer cools down, do you get condensation in the house - maybe not a problem in a typical British drafty house but more of an issue in an air tight self build?

 

@Nickfromwales says that HP dryers have long drying times, that must be simply to do with the size of heat pump they use. In principle, you should be able to condense more water out of the air on the cold side of a heat pump and sent it back into the dryer with less moisture still in it. Or is there a design problem balancing the size of the cooling/condensing and heating sides of the heat pump?

 

I'm still a bit confused!

[Nickfromwales]

I guess they dry at lower temps, so take longer to do the same job as a toasty hot electrical heating element?

[jack]

8 hours ago, LnP said:

Thinking about the heat and material balance around it - since the condenser is being cooled by incoming air from the room, there must be air going back out into the room which has got to be hotter and moister than what went in. Maybe that hot air is OK in winter but not what you want in the summer if you're concerned about over heating? And once that warm moist air coming out of the dryer cools down, do you get condensation in the house - maybe not a problem in a typical British drafty house but more of an issue in an air tight self build?

 

The heat exchanger does not mix moist air from the drum with cooler air from the room.

 

The room air is used to reduce the temperature of the condensing surfaces within the heat exchanger. The warm, moist air from the drum is passed over the cooled condensing surfaces, but on the other side of the surfaces from the room air, hence no mixing. Moisture condenses out and is sent to a drain or container (which must be emptied periodically).

 

While the air from the room is warmed, it does not absorb any moisture, hence there's nothing to condense.

We have a [edited to add:](non heat pump) condenser dryer. While our utility room tends to be warmer than the rest of the house, especially in winter, the temperature difference isn't excessive.

[Dave Jones]

5 hours ago, Nickfromwales said:

I avoided a HP TD as all the manufacturers stated very very long drying times…..

 

our miele is 40 mins tops on full load.

[Nickfromwales]

53 minutes ago, Dave Jones said:

 

our miele is 40 mins tops on full load.

Gutted. I’d have bought one without hesitation but all of the manufacturers literature put me right off. Some saying 4 hour cycles. 

[LnP]

3 hours ago, jack said:

 

The heat exchanger does not mix moist air from the drum with cooler air from the room.

 

The room air is used to reduce the temperature of the condensing surfaces within the heat exchanger. The warm, moist air from the drum is passed over the cooled condensing surfaces, but on the other side of the surfaces from the room air, hence no mixing. Moisture condenses out and is sent to a drain or container (which must be emptied periodically).

 

While the air from the room is warmed, it does not absorb any moisture, hence there's nothing to condense.

We have a heat exchanger dryer. While our utility room tends to be warmer than the rest of the house, especially in winter, the temperature difference isn't excessive.

Indeed, I understood the heat exchanger bit, but I was confused about what air went where! The room air just blows over the condenser and then goes straight back out into the room. If your tumble dryer has a 2.5 kW heater, all the 2.5 kW ends up in your house which is maybe a good thing in winter. If you can move that heat into the rest of the house, you'll save on heating bills and if it reduces the temperature of your utility room, the condenser will work better and you'll dry your clothes faster.

 

The guy in the linked YouTube video isn't a fan of HP dryers and agrees with what @Nickfromwales says about drying times ...  link.

 

Sorry if this hijacked the thread. I know a lot more about tumble dryers now 😀.