Boiling a kettle - OP error!

Freepost

I just received a request from my energy supplier (BG) to supply meter readings to them, which I've now done. While taking the readings I thought, make yourself a cuppa. Normally I use the gas hob but since I also have an electric kettle stuck in the cupboard thought lets try a little experiment between the two methods of boiling water - I really must try to get out more:o

Since I'd just taken the meter readings, I used the gas hob to boil 1.2l of water and then took another meter reading and found that I'd used 0.09 therms or 2.9kWh of gas @ 3.663p/kWh = 10.6p.

I then repeated the water boiling, albeit with fresh water, using an electric kettle. The electric meter didn't record any usage but since I timed the electric kettle at 184sec to boil 1.2l using a kettle with a 2.2kW element the energy used amounts to 0.1124kWh @ 11.073p/kWh = 1.25p.

1.25p Electricity Vs 10.6p Gas has totally shocked me. We tend to use a lot of electric in our home, the bills are quite high so assumed by using what I thought was a cheaper/more efficient energy source, Gas, I was at least saving a little bit of money! I've gone on like this for years!

Of course 1.2l is too much water for one cup of coffee but I imagine that boiling a lesser amount of water will produce a bigger difference between gas and electric.

F

zeupater

Freepost wrote: »

I just received a request from my energy supplier (BG) to supply meter readings to them, which I've now done. While taking the readings I thought, make yourself a cuppa. Normally I use the gas hob but since I also have an electric kettle stuck in the cupboard thought lets try a little experiment between the two methods of boiling water - I really must try to get out more:o

Since I'd just taken the meter readings, I used the gas hob to boil 1.2l of water and then took another meter reading and found that I'd used 0.09 therms or 2.9kWh of gas @ 3.663p/kWh = 10.6p.

I then repeated the water boiling, albeit with fresh water, using an electric kettle. The electric meter didn't record any usage but since I timed the electric kettle at 184sec to boil 1.2l using a kettle with a 2.2kW element the energy used amounts to 0.1124kWh @ 11.073p/kWh = 1.25p.

1.25p Electricity Vs 10.6p Gas has totally shocked me. We tend to use a lot of electric in our home, the bills are quite high so assumed by using what I thought was a cheaper/more efficient energy source, Gas, I was at least saving a little bit of money! I've gone on like this for years!

Of course 1.2l is too much water for one cup of coffee but I imagine that boiling a lesser amount of water will produce a bigger difference between gas and electric.

F

Hi

I'd check the meter or arithmetic again ..... if you used 2.9kWh and it took say 6 minutes to boil, your burner would be rated at 29kW and that's the equivalent of a central heating boiler so your kitchen ceiling would have singe marks on it .... if it took the same time as the electric kettle then that's two central heating boilers so you wouldn't be able to get close enough to turn the kettle off without toasting yourself ......

Something wrong somewhere

HTH
Z

ps/edit .... Gas meters usually read cubic meters and sometimes cubic feet, but not therms as the meter doesn't know the calorific value of the gas flow measured ....

Freepost

zeupater wrote: »

Hi

I'd check the meter or arithmetic again ..... if you used 2.9kWh and it took say 6 minutes to boil, your burner would be rated at 29kW and that's the equivalent of a central heating boiler so your kitchen ceiling would have singe marks on it .... if it took the same time as the electric kettle then that's two central heating boilers so you wouldn't be able to get close enough to turn the kettle off without toasting yourself ......

Something wrong somewhere

Thanks for getting back to me, I suspect my maths!

ps/edit .... Gas meters usually read cubic meters and sometimes cubic feet, but not therms as the meter doesn't know the calorific value of the gas flow measured ....

I have checked again, and you are quite correct the meter measures the gas consumption in cubic ft not Therms, I don't know where that came from. Anyway that's 0.09 ft3 x 2.83 (conversion to m3) x 1.02264 (conversion factor?) x 40.6 (calorific value)/3.6 = 2.93kWh

Still the same reading, so something else must be wrong. The hob burner is a 1kW burner and it was only on about 60% hence no burn marks on the ceiling. Perhaps I'm not reading the meter correctly?

The meter shows 5 digits the least significant digit is coloured red so I assume the red is 1/10 of a unit. To the right is a small dial that is divided with ten markers/positions, so I assume this measures hundredths of a unit. Before boiling the water, the red digit was an 8 and the dial was at position 2. When the water had boiled the red digit was at 9 and the dial was pointing at position 1, so it had used 9 hundredths of a unit, 0.09cubic feet.

What am I doing wrong?

F.

keith_r59

Freepost wrote: »

What am I doing wrong?

Wasting your time working out how much it costs to boil a kettle maybe?

zeupater

Freepost wrote: »

Thanks for getting back to me, I suspect my maths!

I have checked again, and you are quite correct the meter measures the gas consumption in cubic ft not Therms, I don't know where that came from. Anyway that's 0.09 ft3 x 2.83 (conversion to m3) x 1.02264 (conversion factor?) x 40.6 (calorific value)/3.6 = 2.93kWh

Still the same reading, so something else must be wrong. The hob burner is a 1kW burner and it was only on about 60% hence no burn marks on the ceiling. Perhaps I'm not reading the meter correctly?

The meter shows 5 digits the least significant digit is coloured red so I assume the red is 1/10 of a unit. To the right is a small dial that is divided with ten markers/positions, so I assume this measures hundredths of a unit. Before boiling the water, the red digit was an 8 and the dial was at position 2. When the water had boiled the red digit was at 9 and the dial was pointing at position 1, so it had used 9 hundredths of a unit, 0.09cubic feet.

What am I doing wrong?

F.

Hi

Conversion of cubic feet to cubic metres is x0.0283, not x2.83 ....

HTH
Z

Freepost

keith_r59 wrote: »

Wasting your time working out how much it costs to boil a kettle maybe?

I'm inclined to agree with you and as I said at the beginning of the post I really should get out more rather than worrying about spend a few pence more than I should boiling a kettle. The problem is that we spend a fortune each year on gas and never appear warm. Now perhaps that's just the way it is, or perhaps there is something wrong with my meter.

If my maths are correct, then something is wrong for 2.93kWh to be used by a 1kW burner in approx 8mins. Surely it would take almost three hours for the burner to use that much gas!

F

Ben84

zeupater wrote: »

Hi

Conversion of cubic feet to cubic metres is x0.0283, not x2.83 ....

HTH
Z

The difference may be because the meters measure in hundreds of cubic feet?

Is the OP confident about which dial represents a single cubic foot, or 1/10th of one? It does look like it may be a simple power of ten error, particularly because 0.29 kWh of gas sounds like a fairly realistic figure to boil a litre of water.

A confusion may be due to misunderstanding what each dial represents, or understanding this ok but not reading the numbers correctly. You need to round down to the nearest number. The dial's pointer may be between numbers, but we look to the dial next in series for the next number, we do not round up as we would be more than counting the same amount of gas twice. The scale is quantised, the linear way in which the pointers go around the dials is just misleading really.

The bad news is that the dials on a gas meter rotate in different directions (I have no idea why!) so which way to round down depends on direction of rotation.

Your meter may be different to mine, but the very small units in red don't seem to relate to much. They spin around surprisingly fast 24/7 when the only thing lit is the back boiler's pilot flame, which doesn't in fact use that much gas at all.

Freepost

Ben84 wrote: »

The difference may be because the meters measure in hundreds of cubic feet?

Is the OP confident about which dial represents a single cubic foot, or 1/10th of one? It does look like it may be a simple power of ten error, particularly because 0.29 kWh of gas sounds like a fairly realistic figure to boil a litre of water.

A confusion may be due to misunderstanding what each dial represents,

Hi Ben,

Thank you for your response. I've looked at the problem again and whereas I think I am more than capable of reading a meter I have throughout this test been willing to accept that the problem may be down to the OP, namely me.

I've now run the test again but this time with the central heating boiler to obtain a greater throughput, for which the dial on the meter sped round at the speed of light. Okay, slight exaggeration, maybe a fraction less than the speed of light. However I noticed that as the dial made one complete revolution, surprisingly, the counter to the left of it did not increment. Why didn't it increment?

I've now looked at the meter in more detail and the problem is wholly down to me and how I have perceived the meter readout. I'll explain;

The meter, has a five digit numerical display, the display is mechanical - like a ratchet. The extreme right digit is coloured red, so I assumed 1/10th of a unit. To the right of this is a dial that spins around when gas is being used. I had assumed this to measure 1/100th of a unit but it doesn't. In between the 1/10th of a unit numerical display and what I assumed to be the 1/100th of a unit dial is a printed red square where I think the 1/100th of a unit numerical display would be positioned if it had one and that the dial to the right of this measures a 1/1000th of a unit. This seems to fit with your assumptions about a power of ten error!

So the conclusion is OP error but at least its clear :T Now I'll try and get out for bit.

Thanks
F.

166million

So...what's the answer? x

Freepost

166million wrote: »

So...what's the answer? x

42 or at least according to Douglas Adams

Gas or Electricity?

Gas 1.06p
Elec 1.25p

But the above is for 1.2litres which is much more water than required for a basic cuppa.

Also note Electricity is much faster.

F.

mickyduck

Freepost wrote: »

42 or at least according to Douglas Adams

Gas or Electricity?

Gas 1.06p
Elec 1.25p

But the above is for 1.2litres which is much more water than required for a basic cuppa.

Also note Electricity is much faster.

F.

Time=Money