Heat pump drier electricity usage - sanity check for running cost

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lchiu7

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#299298 27-Aug-2022 07:40

Just bought a heat pump clothes drier which the manufacturer rates as 800W. My electricity cost is about 26c/kWh. So if I run the drier for say 2 hours (heat pump driers seem to take longer to dry but boy do they remove a lot of water as evidenced by the water tank) then that's going to cost me about 52c.

I have a rel who is reluctant to use their drier becausev of their high electricity bills but based on that calculation, even if they a normal heating drier at say 2KW running that for an hour which is probably plenty is only about 50c again.

Or do I have some fundamental flaw in my assumptions here?

gcorgnet

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#2960086 27-Aug-2022 07:48

Yes, I think you got that right.

1kWh (so about $0.26 for you) is the amount of energy that is consumed by running the equivalent of a 1000W appliance for 1h. So running a 1000W dryer for 2h will cost you about 2kWh so about $0.52.

Now, the rated power doesn't tell the whol story and appliances don't use that power for the whole time they're on. (eg My washing machine would spend some time drawing 2kw during a 1h cycle but also spends a bunch of time drawing much less than than (the heating is what usually draws a lot of power, the spinning, not so much))
So the cost might be a bit lower than just integrating the power over time due to these fluctuations...

lchiu7

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#2960089 27-Aug-2022 08:05

I thought so. Now to work out how much is it going to cost to charge my new EV and if it's worth putting in a faster charger than just using the wall outlet - time versus money.

raytaylor

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#2960093 27-Aug-2022 08:38

I did a bit of research on this a couple of years ago....

They use less electricity and are cheaper per load dried, but take approx 50% (according to consumer magazines) longer per load.

They dont run as hot so are less damaging to clothing.

However I calculated that the total cost of ownership doesn't always work out as you can buy a cheap dryer for $400 and the electricity cost savings may never break even on the initial purchase price of a more expensive heat pump model over the life of the product.

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RunningMan

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#2960104 27-Aug-2022 09:25

lchiu7:[snip]

Just bought a heat pump clothes drier which the manufacturer rates as 800W.

Suspect that will be the peak power as the compressor starts but the average consumption will be lower than that.

lchiu7

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#2960108 27-Aug-2022 09:43

raytaylor:

However I calculated that the total cost of ownership doesn't always work out as you can buy a cheap dryer for $400 and the electricity cost savings may never break even on the initial purchase price of a more expensive heat pump model over the life of the product.

The item under discussion wasn't about TCO as the dryer has already been purchased, it was whether or not using a dryer really does have a significant impact on your electricity bill which clearly it doesn't for a normal household laundry load.

Blurtie

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#2960167 27-Aug-2022 13:29

We have a samsung heat pump dryer. It's got an energy monitor..

We pretty much use it all the time (2 adults and 2 young boys), would say at least 4/5 loads a week and here are totals for the past few months:

Aug - 15.4kWh
Jul - 22.3kWh
Jun - 16.9kWh
May - 18.3kWh

Obviously those numbers probably mean nothing to you.. But I used 1.2kWh the other day alone for about 3 loads approx 5hrs or so running time (joys of WFH!)

lchiu7

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#2960186 27-Aug-2022 14:14

Blurtie: We have a samsung heat pump dryer. It's got an energy monitor..

We pretty much use it all the time (2 adults and 2 young boys), would say at least 4/5 loads a week and here are totals for the past few months:

Aug - 15.4kWh
Jul - 22.3kWh
Jun - 16.9kWh
May - 18.3kWh

Obviously those numbers probably mean nothing to you.. But I used 1.2kWh the other day alone for about 3 loads approx 5hrs or so running time (joys of WFH!)

Not but that load means about 32c in electricity usage which is not too bad :-)

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Scott3

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#2960233 27-Aug-2022 16:20

lchiu7:

Just bought a heat pump clothes drier which the manufacturer rates as 800W. My electricity cost is about 26c/kWh. So if I run the drier for say 2 hours (heat pump driers seem to take longer to dry but boy do they remove a lot of water as evidenced by the water tank) then that's going to cost me about 52c.

I have a rel who is reluctant to use their drier becausev of their high electricity bills but based on that calculation, even if they a normal heating drier at say 2KW running that for an hour which is probably plenty is only about 50c again.

Or do I have some fundamental flaw in my assumptions here?

2hr x 0.8kW x 26c/kWh = 41.6c

So you are in the right ballpark, assuming the dryer is running the max 800W the whole time.

If you really want to know exactly, you can buy a plug in power meter like the below:

https://www.jaycar.co.nz/mains-power-meter-with-extendable-lcd-display/p/MS6108

lchiu7:

I thought so. Now to work out how much is it going to cost to charge my new EV and if it's worth putting in a faster charger than just using the wall outlet - time versus money.

Consumption varies by EV, driving conditions, driving style etc, but it 17kWh/100km would be a good baseline number to start with.

17kWh/100km x 26c/km = $4.42 / 100km in power costs.

For a petrol car running $2.8 fuel at 7L/100km: 7 x 2.8 = $19.6/100km

26c/kWh sounds like a low user rate. An EV might tip you over to where a standard user plan is better, probable a good idea to go plan power shopping regardless.

How fast you charge doesn't have a significant impact on cost (faster is generally a touch more efficient, but difference isn't really material). Faster charging is most valuable if you want to be able to charge up a bigger batter EV overnight (rather than just replenish 100km or so with a plug in cord), or if you want to fit your charging into an off peak period.

lchiu7

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#2960357 28-Aug-2022 08:52

Scott3:

26c/kWh sounds like a low user rate. An EV might tip you over to where a standard user plan is better, probable a good idea to go plan power shopping regardless.

How fast you charge doesn't have a significant impact on cost (faster is generally a touch more efficient, but difference isn't really material). Faster charging is most valuable if you want to be able to charge up a bigger batter EV overnight (rather than just replenish 100km or so with a plug in cord), or if you want to fit your charging into an off peak period.

Good point. I am now starting to look at moving to a retailer with an EV plan. But the car I have has a WLTP of 440km and so with daily suburban driving can probably get by with a few hours every night off a regular outlet so there might be marginal savings with off peak rates.