Tap hot water in the kettle?
Discussion
If the hot tap that runs from the combi-boiler takes 15-sec to get hot, is it more cost-efficient to add hot water from the hot tap to the kettle and boil it or cold water from the tap and boil?
Taking the kettle to be an average kettle and the price of gas and electricity to be an average?
my understanding is that germs and bacteria found in hot water from the tap would be killed when boiled?!
Taking the kettle to be an average kettle and the price of gas and electricity to be an average?
my understanding is that germs and bacteria found in hot water from the tap would be killed when boiled?!
Can't comment on health but cost efficiency I'd say yes provided the water always wasted while waiting for the hot to come through doesn't cost more than the energy saved! Also the efficiency of a gas boiler may only be achieved once it's been running for a while. With the small amount you're drawing for a kettle fill the boiler innards will have barely heated. A bit like running a car always on choke for short runs.
This based on, IIRC, the cost of gas-hob-boiling kettle vs 'leccie kettle being about the same - lower cost of gas balanced by needing more of it due to the inefficiency of heating on a hob vs higher cost of electricity but less of it.
Using the gas boiler instead of the hob is inherently much more efficient (see caveat above).
One for mythbusters
This based on, IIRC, the cost of gas-hob-boiling kettle vs 'leccie kettle being about the same - lower cost of gas balanced by needing more of it due to the inefficiency of heating on a hob vs higher cost of electricity but less of it.
Using the gas boiler instead of the hob is inherently much more efficient (see caveat above).
One for mythbusters
Brads67 said:
Yup
The thing about not using hot water for the kettle comes from when immersion heaters or back boilers sat as a tank of stored water, which people would not use as drinking water. It tasted off.
Lots of systems now just use mains cold water which is heated quickly by a heat source.
You mean the OP's combi-boiler.The thing about not using hot water for the kettle comes from when immersion heaters or back boilers sat as a tank of stored water, which people would not use as drinking water. It tasted off.
Lots of systems now just use mains cold water which is heated quickly by a heat source.
Our combi-boiler is approx 6 feet from the kitchen sink but the clever sod who did the pipework has kitchen sink as the last outlet.
Waste gallons of water waiting for the hot to arrive.
Brads67 said:
Yup
The thing about not using hot water for the kettle comes from when immersion heaters or back boilers sat as a tank of stored water, which people would not use as drinking water. It tasted off.
Lots of systems now just use mains cold water which is heated quickly by a heat source.
yeah it would be legionaires disease, from warm header tanks or systems not heated to an adequate temp once a day. The thing about not using hot water for the kettle comes from when immersion heaters or back boilers sat as a tank of stored water, which people would not use as drinking water. It tasted off.
Lots of systems now just use mains cold water which is heated quickly by a heat source.
But With combi boilers its all fresh water.
Your combi boiler will be heating 'fresh' cold water on demand, so germs aren't a problem.
But firing and using your combi will use a lot more energy than just using the kettle. And it's another heat cycle of wear and tear for your boiler components.
But gas is a lot cheaper than electricity (during the daytime at least)
Overall I'd side with using solely the kettle, but I don't think there will be much in it.
But firing and using your combi will use a lot more energy than just using the kettle. And it's another heat cycle of wear and tear for your boiler components.
But gas is a lot cheaper than electricity (during the daytime at least)
Overall I'd side with using solely the kettle, but I don't think there will be much in it.
Turfy said:
If the hot tap that runs from the combi-boiler takes 15-sec to get hot, is it more cost-efficient to add hot water from the hot tap to the kettle and boil it or cold water from the tap and boil?
Apart from anything else, if you use water that's been through the combi it loses some of its air content. By the time it's boiled it'll have very little air left. For tea-making, you're not supposed to use boiling water for this reason.You are raising an amount of water to the temperature needed, with the kettle you are heating a quantity slightly more than you need, with a hot water system you are heating far more and you never reach tea making temperature, (only about 68c). A kettle is in fact very efficient because there is little wastage of hot water and you get just under boiling water for tea making.
SpeckledJim said:
Your combi boiler will be heating 'fresh' cold water on demand, so germs aren't a problem.
But firing and using your combi will use a lot more energy than just using the kettle.
And it's another heat cycle of wear and tear for your boiler components.
But gas is a lot cheaper than electricity (during the daytime at least)
Overall I'd side with using solely the kettle, but I don't think there will be much in it.
As I keep telling the misses who keeps running the hot water for nano seconds at a time to rinse every single item. Our boiler probably fires up 100's of times a day but only using a matter of a few litres of water But firing and using your combi will use a lot more energy than just using the kettle.
And it's another heat cycle of wear and tear for your boiler components.
But gas is a lot cheaper than electricity (during the daytime at least)
Overall I'd side with using solely the kettle, but I don't think there will be much in it.
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