[Greenbuilding] cost to run appliance--math help

Speireag Alden speireag at gmail.com
Fri Nov 25 09:58:33 PST 2011

Sgrìobh Ben:

> My house came with a small "Instant hot water dispenser" to keep 1/2
> gallon of water at 190 degrees f. I've had it unplugged since day one
> because i thought it was wasteful expensive to run. My wife wants to
> use it this winter and asked me how much it would cost us. Good
> question. Can anyone give me an estimate on how much it costs to
> run--versus a kettle or a microwave?

	If you are using it in a space which you must still heat after you use it, and that you are using electricity to heat that space, it costs you exactly nothing.  Any "waste heat" simply heats the space it's in.

	If you are using something other than electricity to heat that space, then the effective cost is the difference between the "waste heat" generated by using it, and what it would have cost you to produce the "waste heat" using your space-heating method.

	Practically speaking, you will be using this device so little that you will not notice the difference unless you are one of those types who heats the house by throwing a ball for the dog.

	So, during the heating season, the device is essentially cost-free.  All the heat it generates goes to heat the house anyway.

	In the non-heating-season, the equation is different and I bow to the more math-capable people here.

	But you asked about the winter.

	Hope this helps,


Truth, in matters of religion, is simply the opinion that has survived.
--Oscar Wilde

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