Whats best to heat hot water ,Gas or Electricity

laurieshrimp

When I was younger I was always told it was far cheaper to use Gas to heat your hot water and not use the electric immersion heater.Now with gas being so dear is this still the case.
Can anyone help
Thanks
Laurieshrimp

RuthMarianna

I have been trying to answer this question for years. We heat as much as we can with the immersion on economy 7 cheaper electricity and then anymore we need on gas but I would love to know if I am doing it right?

penrhyn

Gas costs around 4pence per Kwh

Standard rate electricity is approx 14 pence /kwh

If you are on Economy 7 then

Cheap rate around 5 pence /kwh
Day rate around 16 pence /kwh.

Gas is cheaper in every case.
However if you have an old inefficient gas boiler then running the immersion on E7 cheap rate would be cheaper.

Armengar

Even if gas and electric were parity price gas would still be cheaper. An immersion heater heats a tank therefore is more wasteful by nature - even WITH lagging.

It also depends on other factors such as charging bands for units you may pay more for the first X units etc therefore are more likely to use EXPENSIVE gas units first whereas with electricity you would be on the cheaper units faster.

so many variables you cannot put a definite on things but generally gas is cheaper for most people.

HappyMJ

Armengar wrote: »

Even if gas and electric were parity price gas would still be cheaper. An immersion heater heats a tank therefore is more wasteful by nature - even WITH lagging.

I would assume a gas boiler will always be under 100% efficient so that needs to be taken into account. So night rate electric at 5p per unit is the same as a gas boiler at 80% effiency at 4p per unit.

I'm also assuming someone with the option of a immersion heater will also have the gas boiler heat the tank as well. So lagging the tank will not make a difference whether using gas or electric.

penrhyn

Armengar wrote: »

Even if gas and electric were parity price gas would still be cheaper. An immersion heater heats a tank therefore is more wasteful by nature - even WITH lagging.

It also depends on other factors such as charging bands for units you may pay more for the first X units etc therefore are more likely to use EXPENSIVE gas units first whereas with electricity you would be on the cheaper units faster.

so many variables you cannot put a definite on things but generally gas is cheaper for most people.

I was assuming that both gas and electric were used to heat a tank of water.

HappyMJ

penrhyn wrote: »

I was assuming that both gas and electric were used to heat a tank of water.

I was for some reason looking at the SEDBUK database and thought of this thread that I answered earlier.

My boiler is this...

[FONT=Arial, Helvetica, sans-serif]Brand:[/FONT][FONT=Arial, Helvetica, sans-serif]Glow-worm[/FONT][FONT=Arial, Helvetica, sans-serif]
Model name: [/FONT][FONT=Arial, Helvetica, sans-serif]Spacesaver [/FONT][FONT=Arial, Helvetica, sans-serif]
Model qualifier:[/FONT][FONT=Arial, Helvetica, sans-serif]50f [/FONT][FONT=Arial, Helvetica, sans-serif]
Model Identity no.:[/FONT][FONT=Arial, Helvetica, sans-serif]4131370
[/FONT][FONT=Arial, Helvetica, sans-serif]First Manufactured:[/FONT][FONT=Arial, Helvetica, sans-serif]
Last Manufactured:[/FONT][FONT=Arial, Helvetica, sans-serif]1989
[/FONT][FONT=Arial, Helvetica, sans-serif]Product Index Number:[/FONT][FONT=Arial, Helvetica, sans-serif]001370[/FONT]

Right now if you look at the efficiency of it...it's as follows..
[FONT=Arial, Helvetica, sans-serif]SAP 2009 annual efficiency:[/FONT][FONT=Arial, Helvetica, sans-serif]68.0%[/FONT][FONT=Arial, Helvetica, sans-serif]
SAP winter seasonal efficiency:[/FONT][FONT=Arial, Helvetica, sans-serif]69.0%[/FONT][FONT=Arial, Helvetica, sans-serif]
SAP summer seasonal efficiency:[/FONT][FONT=Arial, Helvetica, sans-serif]59.0%[/FONT][FONT=Arial, Helvetica, sans-serif]
Comparative hot water efficiency:[/FONT][FONT=Arial, Helvetica, sans-serif]39.7%[/FONT][FONT=Arial, Helvetica, sans-serif]
SAP 2005 Seasonal efficiency:[/FONT][FONT=Arial, Helvetica, sans-serif]68.0%[/FONT][FONT=Arial, Helvetica, sans-serif]
Efficiency category:[/FONT][FONT=Arial, Helvetica, sans-serif]SAP Estimated[/FONT][FONT=Arial, Helvetica, sans-serif]
SAP equation used:[/FONT]0[FONT=Arial, Helvetica, sans-serif]
Power: [/FONT][FONT=Arial, Helvetica, sans-serif]14.65 kW[/FONT]
[FONT=Arial, Helvetica, sans-serif]
[/FONT]Does that mean for water heating I could use the 3kw electric immersion for 90 minutes every night in summer and that would cost me 4.49p * 4.5kWh = 20.2p per night

Or on gas for the same heat should I use the comparative hot water efficiency figure of 39.7% (and it takes about 45 minutes to heat a tank from cold) it would be 2.518p * 4.5kWh/0.397 = 28.5p per night. That's a big difference..... It's seems as if its 40% more expensive using gas. I must have something wrong here... Can anyone confirm?

penrhyn

I think you are on to something there, I had not thought how inefficient a gas boiler would be just heating the water.

HappyMJ

penrhyn wrote: »

I think you are on to something there, I had not thought how inefficient a gas boiler would be just heating the water.

Just thinking about it too electric is required to operate the boiler itself and to pump the water from the boiler then around the tank then back to the boiler the pump is rated at 110W and the boiler at 55W, then when it's finished heating the tank there is heat left in the water pipes from the boiler to the airing cupboard which in summer is completely wasted.

Of course my boiler is rather old so I'm sure some newer boilers would be more efficient.