Gas heating vs Electric heating

Mstty

Ignite said:

So the big question is at what point would it work out cheaper to use electric heaters over the gas boiler.

In simple terms when the price per kWh of electricity is less than the price per kWh of gas.

Add in the complexity of an Air Source Heat Pump or even heat pump air con units that can also heat then that's another matter.

pochase

Mstty said:

Ignite said:

So the big question is at what point would it work out cheaper to use electric heaters over the gas boiler.

In simple terms when the price per kWh of electricity is less than the price per kWh of gas.

Add in the complexity of an Air Source Heat Pump or even heat pump air con units that can also heat then that's another matter.

I think you mean when the price per KWh "of heat" generated by electricity is cheaper than the price per KWh "of heat" generated by gas.

armistice

Ignite said:

So the big question is at what point would it work out cheaper to use electric heaters over the gas boiler.

Estimating that your boiler is probably 60% efficient at turning gas into heat vs Standard electrical heating at 100% efficient:

19.1 p/kw elec  ~  19.1 / 100 * 60 = 11.46 p/kw gas  

So if your gas is more than 11.46p per kw you would save by using electrical heating.

BUFF

Ignite said:

So the big question is at what point would it work out cheaper to use electric heaters over the gas boiler.

as per armistice, but there will be additional losses in your wet ch system in addition to just the boiler's own efficiency.

Let us assume that electric heating is 100% efficient.
& let us assume that your boiler is running at 60% efficiency but there are additional losses in the system so 50% overall efficiency (it makes the maths easy  ). 
For your existing system* & existing heating pattern**, given those assumptions the break even point is when electricity prices are 2x per kWh than gas. Any lower multiple than that & you are cheaper using electricity than gas. With your 19.1p kWh rate that means gas over 9.55p kWh.
If your overall system efficiency were 55% rather than 50% it would be 10.50p.

* i.e you don't have to go out & buy electric heaters or change your boiler
**e.g. if you decided that you could get away with heating only 1 room at a time instead of the whole house (although I would not recommend it) that could have an influence on the answer

Xbigman

BUFF said:

Ignite said:

So the big question is at what point would it work out cheaper to use electric heaters over the gas boiler.

as per armistice, but there will be additional losses in your wet ch system in addition to just the boiler's own efficiency.

Let us assume that electric heating is 100% efficient.
& let us assume that your boiler is running at 60% efficiency but there are additional losses in the system so 50% overall efficiency (it makes the maths easy  ). 
For your existing system* & existing heating pattern**, given those assumptions the break even point is when electricity prices are 2x per kWh than gas. Any lower multiple than that & you are cheaper using electricity than gas. With your 19.1p kWh rate that means gas over 9.55p kWh.

* i.e you don't have to go out & buy electric heaters or change your boiler
**e.g. if you decided that you could get away with heating only 1 room at a time instead of the whole house (although I would not recommend it) that could have an influence on the answer

My last boiler service the engineer gave me a printout of my boilers flue test that gave a % of efficiency. Do you have one of those? It will take the guess work out of it. At that point my 11 year old boiler was still 83.9% efficient. You might be surprised by the figures for your boiler.


Darren 

BUFF

Xbigman said:

My last boiler service the engineer gave me a printout of my boilers flue test that gave a % of efficiency. Do you have one of those? It will take the guess work out of it. At that point my 11 year old boiler was still 83.9% efficient. You might be surprised by the figures for your boiler.

His started out as G-rated so under 70% even new. But, yes, if he has that then certainly useful info.

JohnPo

As everyone's situation is different, can I pose a question around my own setup?

Currently on Octopus Go so have 4 hours - 12.30am to 4.30am where the electricity is 'cheap' at 7.5p KWhr.  Quite a large space heating requirement over 20,000 KWhr with a modern 'heat only' condensing boiler and radiators. The Gas tariff is Octopus tracker v3, with cap of 11p KWhr and ever day this week it has been at the cap. Currently have a timed immersion heater to take advantage of the overnight cheap rate, large tank with a  27 inch immersion heater that only heats the top 1/3rd of the tank, so only using gas for cooking and occasionally topping up during the day the hot water.

I am working on the assumption that the differential pricing is a bit of an anomaly, so not going invest much in new kit at the moment. 

So come the autumn / winter would it be sensible to use any overnight 'cheap rate' to provide some background heating at night via fan heaters / electric radiators?

BUFF

JohnPo said:

So come the autumn / winter would it be sensible to use any overnight 'cheap rate' to provide some background heating at night via fan heaters / electric radiators?

do you need it to be warm when you are tucked up in bed though?
Are you in the house all day or up & out fairly quickly?

pochase

Even if it is "cheap" it would be still an additional (unnecessary?) cost.

JohnPo

BUFF said:

JohnPo said:

So come the autumn / winter would it be sensible to use any overnight 'cheap rate' to provide some background heating at night via fan heaters / electric radiators?

do you need it to be warm when you are tucked up in bed though?
Are you in the house all day or up & out fairly quickly?

In most of the time, we keep the main thermostat in the heated hallway to 16 degrees during the day and 14 at night, just wondering whether to try dropping the night setting down a bit and using the cheaper supplementary electric heating. Having thought about it I am probably going struggle to get things setup in way which is not wasteful.  Any other ideas are of course welcome.