Energy ratings for tumble dryers

zeupater

Sterlingtimes wrote: »

I mentioned to Mrs Sterling this evening that it is not every husband who would set up a couple of test rigs to measure her laundry energy usage. She did not seem very impressed.

... just wait until you try to 'train' her to automatically check the weather forecast as part of the appliance usage decision making process .... :rotfl:

Cardew

Agreed I wouldn't vouch for their arithmetic.


It is interesting that condensing dryers now lead the tables for efficiency; even without considering the point you made about vented dryers sucking warm air out of the house.


I also think it an unrealistic test to take each cycle as 6Kg of cotton.

Sterlingtimes

I have learned a lot over the past week with many surprises.


After a week's monitoring, the laundry component of our energy usage is far lower than my expectation. The annual projection would now be:


tumble dryer (B-rated) 1,338 kWh a year
washing machine (A++-rated) 699 kWh a year
Laundry uses 2,007 kWh a year out of 8,275 kWh a year, 24%.


So the B-rated tumble dryer would cost £150 a year in electric costs.


A gas dryer would in efficiency terms 1.789/3.980 = 0.45 of the kWh of the electric dryer. And the cost of gas would be 3.6855/11.2035 = 0.32 of the price of a kWh. So the dryer would only cost £22 a year in energy use.


Without considering solar contribution, if I replaced my perfectly good tumble dryer with a gas one at £300 + £150 installation, I would get pay back in 3.5 years. An electric heat pump one is not worth considering on this basis (unless I had to junk my good dryer).


So the outstanding question is how much will solar contribution will change the payback period. More measurement and more work to be done, I think.

zeupater

Sterlingtimes wrote: »

I have learned a lot over the past week with many surprises.

After a week's monitoring, the laundry component of our energy usage is far lower than my expectation. The annual projection would now be:

tumble dryer (B-rated) 1,338 kWh a year
washing machine (A++-rated) 699 kWh a year
Laundry uses 2,007 kWh a year out of 8,275 kWh a year, 24%.

So the B-rated tumble dryer would cost £150 a year in electric costs.

A gas dryer would in efficiency terms 1.789/3.980 = 0.45 of the kWh of the electric dryer. And the cost of gas would be 3.6855/11.2035 = 0.32 of the price of a kWh. So the dryer would only cost £22 a year in energy use.

Without considering solar contribution, if I replaced my perfectly good tumble dryer with a gas one at £300 + £150 installation, I would get pay back in 3.5 years. An electric heat pump one is not worth considering on this basis (unless I had to junk my good dryer).

So the outstanding question is how much will solar contribution will change the payback period. More measurement and more work to be done, I think.

Hi

Are you sure that there's no double accounting in the above? ....

... The energy consumption label for a 7kg gas tumble (ECO43A) dryer states 256kWh/year and a B rated 7kg (random select Hotpoint TVM570P) is 267kWh .... almost exactly the same, so the only difference would be the relative fuel cost - so (your costs) 1338kWh/year of electricity would cost £149.90, with gas being £49.31 .... a difference of £100/year ... then of course, there's the cost of the electricity require to actually 'tumble' a gas dryer to account for .... I'd hazard a guess that 45% mentioned would represent the relative running costs, not energy efficiency ....

As for solar contribution .... I don't know how many times you want to use the solar contribution. Effectively, if you generate ~3500kWh/year and use (say) ~1000kWh in baseline usage you've only got 2500kWh spare to use .... from this you expect to have proportional diversion to feed as much as possible towards a massive ~7000kWh of DHW requirement and a further 2000kWh in laundry .... there's probably a dishwasher which could be run on timer somewhere too, then there's the iron for all that laundry ....

You just cannot allocate more generation than you have ... with that kind of demand, where the generation goes will vary not only day by day according to time of year, but hour by hour within each of those days .... even with proportional diversion you'll struggle to use all you generate - the only way that this is possible is to have a continuous baseline demand which is greater than the peak capacity of your system. You can really get into a state where you're overanalysing .... at the moment it looks like there's an intent to spend money to maximise the use of generation in order to save money on energy whilst totally ignoring the elephant in the room, that being addressing and reducing the currently massive level of energy consumption .... 8275kWh/year is almost exactly 2.5x the average households usage (3300kWh), so now you've discovered where ~2000kWh goes, it's time to use those new monitors to do some more detective work - excluding laundry, you're still using almost double what the average household uses, and theirs includes laundry .... so what's using it ??

HTH
Z

1961Nick

zeupater wrote: »

............. so what's using it ??

HTH
Z

Can I hazard a guess.......Mrs Sterlingtimes?:laugh:

You're not alone ST, 9594kWh last year.:eek:

Sterlingtimes

zeupater wrote: »

Are you sure that there's no double accounting in the above? ....

... The energy consumption label for a 7kg gas tumble (ECO43A) dryer states 256kWh/year and a B rated 7kg (random select Hotpoint TVM570P) is 267kWh .... almost exactly the same, so the only difference would be the relative fuel cost - so (your costs) 1338kWh/year of electricity would cost £149.90, with gas being £49.31 .... a difference of £100/year ... then of course, there's the cost of the electricity require to actually 'tumble' a gas dryer to account for .... I'd hazard a guess that 45% mentioned would represent the relative running costs, not energy efficiency ....

Thank you, zeupater. You raise several interesting points. Thank you for taking the time to post: this may prove valuable in my calculations.


I was going to dismiss this part of your posting, but when I checked further, I think you may be correct.


So my existing dryer is the Indesit vented IDV75. It is variably shown by different retailers as C-rated or B-rated. I had based calculation on the published cotton cycles, i.e. ECO43A an A+ machine gives 1.6 kWh per cotton cycle whereas the IDV75 gives 3.98 kWh per cotton cycle. You quite correctly use the alternative annual consumption figures which indicates that the two machines are of equal efficiency.


I thought that the published cotton cycles were the means by which the energy efficiency ratings were assessed.


If your calculation is the correct one (as it may be) then the payback period is longer. The investment looks considerably less attractive.

Sterlingtimes

1961Nick wrote: »

Can I hazard a guess.......Mrs Sterlingtimes?:laugh:

You're not alone ST, 9594kWh last year.:eek:

If the people in the house behave like the ecowarriors in the comedy "The Good Life" or the film "Nuts in May" then they are off to a very good start because efficiencies are brought to fruition through ideal behaviour.


My problem is that for my family, I have got to design the infrastructure to achieve energy efficiencies. Using phases like, "do you think that this is Blackpool Illuminations?" carry no weight. The energy is being burned while I am at work.

Sterlingtimes

zeupater wrote: »

... ignoring the elephant in the room, that being addressing and reducing the currently massive level of energy consumption .... 8275kWh/year is almost exactly 2.5x the average households usage (3300kWh), so now you've discovered where ~2000kWh goes, it's time to use those new monitors to do some more detective work - excluding laundry, you're still using almost double what the average household uses, and theirs includes laundry .... so what's using it ??

Yes, more work for me to do. The OVO "people like me" average gives 6,157 kWh per year of electricity. I am making some headway on moving from 8,275 towards 6,157 even without the solar.

zeupater

Sterlingtimes wrote: »

Yes, more work for me to do. The OVO "people like me" average gives 6,157 kWh per year of electricity. I am making some headway on moving from 8,275 towards 6,157 even without the solar.

Hi

I've no idea how OVO compare households ... being an energy supply company they have absolutely no incentive to make you feel bad about being a high energy user and using more than necessary - even if they claim to, so if the profile that they have says that you live in a large un-insulated property with loads of halogen lights on all day, 4 plasma TVs on all day, everything possible on standby all day, a 'stay-warm' kettle, outdoor security lights on all day, heating on at 25C all year round, dishwasher used everyday with partial loads, and 3 full loads of washing per day then of course a direct comparison would be made to "people like me" ....

The electricity used in dual fuel properties should logically be related more to the number of occupants and their energy awareness more than the size of the property .... if you think about it, the only major usage which should be related to size would be lighting and these days that's a really easy item to address even if you can't convince everyone in the household to turn unneeded lights off .... something quite simple like having 15 40W halogen bulbs on in the kitchen for 16 hours/day whether they're needed or not consumes an astounding 3500kWh year and many people don't really realise that this is the case when designing their new decor .... almost £500/year to light a room which is only used occasionally, whilst spending £100 on LED equivalents would cut the bill to closer to £50 ....

Effectively forget the "people like me" and find out what's consuming energy and costing money in your own property ... with a combination of plug-in monitors and a whole house monitor you should be able to get a very good idea within a couple of hours if you're prepared to go around the house switching things on & off ...

HTH
Z