Hot water - cheaper from gas boiler or the kettle? For small-ish amounts

rosamy52

So my query is - is hot water cheaper from gas boiler or the kettle? For small-ish amounts like washing up. I know it probably seems a daft question but if anyone knows I'd be grateful! If it helps I'm on a prepayment meter for gas and electricity with Octopus. Thank you. 

Reed_Richards

Run your hot tap into a measuring jug and measure how much cold water you have to run-off before the tap runs hot.  That is the amount of hot water that is wasted because it gets left behind in the pipes after you have used the hot tap.  If you can wash up in about half the amount of water you have measured then that is about the break-even point with using the kettle.  If it takes less than that to wash up then use the kettle.  If it takes more then use the hot tap.

ctdctd

My condensing combi boiler uses a measured 1kWh of gas and 15 litres of water to heat and then fill a washing up bowl.

After the April rise, this will cost me 7p for gas and 4p for water.

Boiling 2 litres of water in my 2kW kettle takes about 6 minutes and costs 6p for electricity.

If that is mixed with 5 litres of water in the sink, water will cost about 2p

So, if my maths is right, the kettle is cheaper in my case!

Mind you, 2 litres of boiling mixed with 5 litres of cold might not fill the sink and be a bit chilly!

 

FreeBear

ctdctd said: Mind you, 2 litres of boiling mixed with 5 litres of cold might not fill the sink and be a bit chilly!

Use a plastic bowl. It doesn't suck up heat like a s/s sink would, and you don't need as much water. Most of the time, I'm using less than 3l of water per wash in a bowl.

ctdctd

FreeBear said:

ctdctd said: Mind you, 2 litres of boiling mixed with 5 litres of cold might not fill the sink and be a bit chilly!

Use a plastic bowl. It doesn't suck up heat like a s/s sink would, and you don't need as much water. Most of the time, I'm using less than 3l of water per wash in a bowl.

I do use a plastic bowl - I think it holds about 9 litres so about 7 litres with the dirty plates included. I'm a one miserable old git band so only wash up once a day but do use a full bowl!

macman

Gas is still much cheaper than electricity per kWh. If you have a hot tank and you heat more water than used, any escaping heat serves to warm the house anyway in winter, so it's not actually wasted.
Using a dishwasher will be cheaper on water saving than washing up by hand.

QrizB

ctdctd said:

Mind you, 2 litres of boiling mixed with 5 litres of cold might not fill the sink and be a bit chilly!

Two litres at 100C plus five at 10C will give an end temperature of around 35C. Colder than I'd choose for washing up but it'll probably be good enough for a single-person's dishes.

Chrysalis

Depends on type of boiler?

My old rust bucket doesnt heat on demand, has to be on for 30-40 minutes to get hot water.  Ok for baths, inefficient for dishes.  I try to fill the sink when I heat it for baths.

Reed_Richards

ctdctd said:

My condensing combi boiler uses a measured 1kWh of gas and 15 litres of water to heat and then fill a washing up bowl.

After the April rise, this will cost me 7p for gas and 4p for water.

Boiling 2 litres of water in my 2kW kettle takes about 6 minutes and costs 6p for electricity.

If that is mixed with 5 litres of water in the sink, water will cost about 2p

So, if my maths is right, the kettle is cheaper in my case!

Mind you, 2 litres of boiling mixed with 5 litres of cold might not fill the sink and be a bit chilly!

 

It's not fair to compare the cost of 15 litres of water heated by gas with the cost of 7 litres of water heated by electricity.  Using those figures, 14 litres of water heated by electricity would cost 16p compared to 11p for 15 litres of water heated by gas.  So gas is the cheaper option in a fair comparison.

QrizB

Reed_Richards said:

ctdctd said:

My condensing combi boiler uses a measured 1kWh of gas and 15 litres of water to heat and then fill a washing up bowl.

After the April rise, this will cost me 7p for gas and 4p for water.

Boiling 2 litres of water in my 2kW kettle takes about 6 minutes and costs 6p for electricity.

If that is mixed with 5 litres of water in the sink, water will cost about 2p

So, if my maths is right, the kettle is cheaper in my case!

Mind you, 2 litres of boiling mixed with 5 litres of cold might not fill the sink and be a bit chilly!

 

It's not fair to compare the cost of 15 litres of water heated by gas with the cost of 7 litres of water heated by electricity.  Using those figures, 14 litres of water heated by electricity would cost 16p compared to 11p for 15 litres of water heated by gas.  So gas is the cheaper option in a fair comparison.

I could be wrong but I think ctdctd is allowing for six litres of "dead" hot water in the pipes leading to the sink.

Otherwise they'd be trying to fit fifteen litres into their nine-litre washing-up bowl.

rosamy52

Thanks everyone for your thoughts, I'll do some experimenting!