What's the best way to get hot water with a minimum of energy?

Question

while doing the washing up i wondered which of the following would use the least amount:

- boiling the kettle (electric), and adding that to the washing-up bowl

- running the tap until the water heated up (up to a few minutes - gas boiler at the other end of the flat)

- boiling water on the gas hob

anyone know for sure?

Answer 1

When I'm washing up, I begin to use the water as soon as it comes out of the tap, I fill plug the sink as I'm rinsing to allow a soaking area. For most things all you need is water, not hot water, by the time I've finished washing the water is hot and I rinse. My kitchen is about as far away from my water heater as possible while still in the same building, I have no idea how many gallons it would take if I waited for hot water.

It seems like a waste of energy to boil water in the kitchen, but if you do, Microwave uses less than gas, gas less than electric kettle or electric stove.

Answer 2

boil water on the hob but only as much as you need .

Answer 3

The most efficient way I can think of to get that hot water with the minimum of energy expenditure would be to get someone to tap in to the hot water line at or near the water heater so you can shorten the distance the hot water has to travel.



Get a container of whatever size you require and place it under the spigot and fill it with hot water and carry it to wherever you need it.



Why would that work? Because you aren't wasting as much energy as you would allowing all that heat to dissipate in all that copper tubing running from the heater to wherever you need it.

After you get your hot water..the lines are still hot and slowly lose heat. (wasted energy).

But if you get it almost at the water heater, there's very little energy lost to heat dissipation in the copper.

Its called squeezing a quarter out of a nickel.

Hmmm, Send that one to Mythbusters. lol

Good Luck!

Answer 4

Try a solar water heater. In Japan many of the houses have water heaters on the top of the roof. The sun heats the water during the day. We just bought for camping a solar water heater that is a bag you fill with water and hang in the sun during the day. I think it contains a gallon and a half, and there was a bigger size available. I thought the smaller size would be easier to carry. You wouldn't have to go camping, of course. Just hand it one the sunny side of your house, and you ought to have enough warm water to wash your dishes or do a shampoo.

Answer 5

mostly good ideas there already although I take issue with the microwave being more efficient.

Few issues to remember; electricity is a more useful form of energy than heat, it usually too a lot of energy to make the electricity in the first place, so using it to make heat again is a bit silly. Say the electricity you use comes from a coal fired plant, then at the power station 50% of the energy in the coal, got wasted to make electricity. By the time you get to use the electricity in your home further losses have occurred in the power lines and transformers along the way.  You maybe only receive 33% of the original energy in the coal. So even if burning gas to boil your water is using 3 times as much energy as an electric kettle, the net energy is the same but you would be producing less green house gases as gas gives more energy per kilo of CO2 than coal. I doubt that boiling on the stove will take 3 times as much energy.

Another thing, if you only need warm water, do not boil the water, just warm it. It is more efficient to just warm all the water than to heat some of it very hot then mix it with cold. So only heat the water to the temperature you really need it at. (less losses to the air, less heating of the kettle/jug whatever).

The idea given of using all the water out of the hot water system sounds a good idea as by the time you have filled your bowl/sink the water will be just right. The losses in the piping are probably not that big. The gas hot water system is a very efficient way of heating water, nearly 80-90% of the energy in the gas is converted to heating the water, so even substantial losses in the piping will not make this worse than using any form of electric cooking/heating unless the electricity came from a non-fossil source.

If your electricity is from a renewable source or nuclear, you may as well use it and forget the gas altogether.

Answer 6

Using the hot water in your hot water heater should be the most efficient.  The water is already being maintained at that temperature, and it only costs a little more energy to heat the cold water that's added to the tank to replace it.

For boiling water, the electric kettle is much, much more efficient than the stove.  I know that for a fact.  All of the heat generated goes into the boiling, with some lost through the sides and top.  On the stove, much of the heat generated will be lost to the surroundings without going through the water first.

If you're really into it and have a very sunny window or better yet a sunny ledge or balcony you have access to, you may consider making or buying a small solar oven.  I'm too far north to get one to supplement or replace my conventional oven economically, but the technology is so nifty that I intend to make a small one just for boiling the tea I drink constantly.  It's a shame we don't have enough solar energy for baking here, but heating water is easier and should work just fine in three seasons.

A jumping-off point for solar ovens, made from reflective material, glass, or a lens, is here:  http://en.wikipedia.org/wiki/Solar_cooke...

Answer 7

I'm in the same situation as yourself - and asked a similar question about the most efficient way to get a good coffee (nobody knew deffinately)

I would say whichever wastes less in doing it.

Heating water from a low temp to a high one will always take the same ammount of energy, so you need a method that has a high eficiency. This means reduced losses.

If you have a hot water tank - Buy another jacket for it (you can take it with you), and around that - add any bubblewrap you can find. This will ensure you don't waste energy. If you are on economy heating - turn your daytime heating cycle off completely.

This will probably be the most efficient, although you will loose out on the 'cold leg' of pipe.

If you are cooking, then putting a pan of water in the oven as you take out the meal will soak up remaining heat - and help when it's time to wash up.

If you fill a 5l bottle with water from the tap, and empty this into the kettle when needed, this will save energy, as water comes out fairly cold from the tap, but rises to room temperature from the surroundings - therefore the kettle needs less energy input.

So in short - reduce losses, but boiling on gas hob probably the least efficient, Boiler - because of distance also not good - so looks like kettle from a warmed supply.

Answer 8

Well, your water heater will be more efficient than boiling water on your stove or hob.

I wouldn't really worry about it, but I've seen people successfully heat their water by piping it through ABS (black) plastic pipes on their roof and letting the sun bake them.  It's not very consistent though and will be influenced by weather temps outside.  However, it may be a good way to use a bit less gas/electric on the water heater by piping already warmed water into it.  However, if you're in a flat I dunno that you'll be able to do that.