Electric Boiler vs Gas Boiler

GValue

@csswiiftThank you for asking this question. I'm currently exploring this too, because my old gas boiler needs replacing and because it's in a chimney (not a balanced flue for gas safety inspection) it needs to be moved if I want to use gas. My first quote from British Gas was £6,000
My understanding is that the gas Kwh price is flawed because the BtU conversion is 1 kwh = 3412 btu and electric boilers modulate.

doodling

Hi,

GValue said:

@csswiiftThank you for asking this question. I'm currently exploring this too, because my old gas boiler needs replacing and because it's in a chimney (not a balanced flue for gas safety inspection) it needs to be moved if I want to use gas. My first quote from British Gas was £6,000
My understanding is that the gas Kwh price is flawed because the BtU conversion is 1 kwh = 3412 btu and electric boilers modulate.

The gas kWh price is perfectly valid as a comparison to the electric kWh price if you are using them both for heating.  You do need to account for the lower efficiency of a gas boiler (assume around 90%) rather than the 100% efficiency of electric heating.

I would be surprised if electric boilers modulate - that would add cost and there isn't really any efficiency to be gained by modulation with electric boilers (unlike gas).

The conversion to BTU is irrelevant.  Does anybody use BTU any more? - I was brought up on both metric and imperial measurements for speed, length, etc. but I draw the line well before using BTU.  If you are going to talk about energy then just use kWh (or Joules if you really want to stick to SI units).

Reed_Richards

GValue said:

My understanding is that the gas Kwh price is flawed because the BtU conversion is 1 kwh = 3412 btu and electric boilers modulate.

I'm not sure what this even means but all modern gas boilers modulate.  This is useful because:

1. It mitigates against the gas boiler running in very short on/off cycles which could reduce efficiency.
2. It allows the gas boiler to run at a lower water temperature, which improves its efficiency because you get more heat recoverd from condensation in a condesning boiler.

The only advantage I can think of in having an electric boiler modulate is that it enables the heating pipes to be cooler so any sections of pipe that are outside the insulated fabric of the building (in a loft, for example) will lose heat less rapidly.

  

matelodave

Generally even if an electric boiler could modulate (its pretty easy to do with a PWM controller) you still come up against the fact that leccy is three times the cost of gas for the same amount of heat. So however well you control it it will still triple the cost of your heating bills compared with gas.

The only way to use leccy with a usage cost that comes anywhere close to gas is with a heatpump but even then its still more expensive and will be until the cost of leccy is reduced by quite a bit or the cost of gas in increased to take more of the "Eco" burden which is currently lumped onto the cost of electricity.

TheElectricCow

matelodave said:

The only way to use leccy with a usage cost that comes anywhere close to gas is with a heatpump but even then its still more expensive and will be until the cost of leccy is reduced by quite a bit or the cost of gas in increased to take more of the "Eco" burden which is currently lumped onto the cost of electricity.

This is generally true, but it is potentially worth pointing out the one caveat to this where electric would currently be cheaper than gas - albeit it does require an awfully specific set of circumstances.

IF someone who was living in the Eastern supply region was on an E7 tariff with EDF, their night rate for electric would actually be cheaper than the unit rate for gas, even if we ignore any differences in efficiency (which would be in electric’s favour anyway).

The property would also need to be capable of retaining enough heat to not require a top up during the day (or have storage heaters), and naturally the installed system would need to be able to store hot water for day use. But in that rather specific scenario, just basic electric resistive heating would in fact work out a bit cheaper than even the most efficient gas boilers out there with central heating. 

Considering an estimated 90% efficiency of gas, electric would be 8.59p/kWh compared to about 11.34p/kWh of heat with gas. 

If a heat pump was added to the equation the cost effectiveness vs gas would increase even further, assuming you only run it at night or are able to secure a similarly low rate from the likes of an Octopus specialised tariff.

The only other cost implication to think about is if enough other general daytime energy use (dishwashers, washing machine, etc.) could be shifted to night to make up for the increased day rate. That part would depend mostly on the household itself and the occupant’s habits though.

Again, not relevant to the majority of people, but for the few who are able to take advantage of such a low electric rate there are cost savings vs gas to be had at least until prices change.

matt_drummer

TheElectricCow said:

matelodave said:

The only way to use leccy with a usage cost that comes anywhere close to gas is with a heatpump but even then its still more expensive and will be until the cost of leccy is reduced by quite a bit or the cost of gas in increased to take more of the "Eco" burden which is currently lumped onto the cost of electricity.

This is generally true, but it is potentially worth pointing out the one caveat to this where electric would currently be cheaper than gas - albeit it does require an awfully specific set of circumstances.

IF someone who was living in the Eastern supply region was on an E7 tariff with EDF, their night rate for electric would actually be cheaper than the unit rate for gas, even if we ignore any differences in efficiency (which would be in electric’s favour anyway).

The property would also need to be capable of retaining enough heat to not require a top up during the day (or have storage heaters), and naturally the installed system would need to be able to store hot water for day use. But in that rather specific scenario, just basic electric resistive heating would in fact work out a bit cheaper than even the most efficient gas boilers out there with central heating. 

Considering an estimated 90% efficiency of gas, electric would be 8.59p/kWh compared to about 11.34p/kWh of heat with gas. 

If a heat pump was added to the equation the cost effectiveness vs gas would increase even further, assuming you only run it at night or are able to secure a similarly low rate from the likes of an Octopus specialised tariff.

The only other cost implication to think about is if enough other general daytime energy use (dishwashers, washing machine, etc.) could be shifted to night to make up for the increased day rate. That part would depend mostly on the household itself and the occupant’s habits though.

Again, not relevant to the majority of people, but for the few who are able to take advantage of such a low electric rate there are cost savings vs gas to be had at least until prices change.

It also works if you have a lot of solar panels and batteries. Then you can buy all of your electricity to run your heat pump at the off peak rate, miles cheaper than gas!

Heat pumps are generally 300% efficient or better, electricity at 34p is the same as gas at 10.2p (10.20/0.9 = 11.33 x 3 = 34.00)

Apart from the capital outlay, an air source heat pump will be the same or cheaper to run than a gas boiler.

Heat pumps run at low flow temperatures, you will never heat the property enough at night to not require heating during the day however low your heat loss is.

TheElectricCow

matt_drummer said:

TheElectricCow said:

matelodave said:

The only way to use leccy with a usage cost that comes anywhere close to gas is with a heatpump but even then its still more expensive and will be until the cost of leccy is reduced by quite a bit or the cost of gas in increased to take more of the "Eco" burden which is currently lumped onto the cost of electricity.

This is generally true, but it is potentially worth pointing out the one caveat to this where electric would currently be cheaper than gas - albeit it does require an awfully specific set of circumstances.

IF someone who was living in the Eastern supply region was on an E7 tariff with EDF, their night rate for electric would actually be cheaper than the unit rate for gas, even if we ignore any differences in efficiency (which would be in electric’s favour anyway).

The property would also need to be capable of retaining enough heat to not require a top up during the day (or have storage heaters), and naturally the installed system would need to be able to store hot water for day use. But in that rather specific scenario, just basic electric resistive heating would in fact work out a bit cheaper than even the most efficient gas boilers out there with central heating. 

Considering an estimated 90% efficiency of gas, electric would be 8.59p/kWh compared to about 11.34p/kWh of heat with gas. 

If a heat pump was added to the equation the cost effectiveness vs gas would increase even further, assuming you only run it at night or are able to secure a similarly low rate from the likes of an Octopus specialised tariff.

The only other cost implication to think about is if enough other general daytime energy use (dishwashers, washing machine, etc.) could be shifted to night to make up for the increased day rate. That part would depend mostly on the household itself and the occupant’s habits though.

Again, not relevant to the majority of people, but for the few who are able to take advantage of such a low electric rate there are cost savings vs gas to be had at least until prices change.

It also works if you have a lot of solar panels and batteries. Then you can buy all of your electricity to run your heat pump at the off peak rate, miles cheaper than gas!

Heat pumps are generally 300% efficient or better, electricity at 34p is the same as gas at 10.2p (10.20/0.9 = 11.33 x 3 = 34.00)

Apart from the capital outlay, an air source heat pump will be the same or cheaper to run than a gas boiler.

Heat pumps run at low flow temperatures, you will never heat the property enough at night to not require heating during the day however low your heat loss is.

A valid point about the flow temp, hadn’t considered that part! I would have thought an Air to Air system might manage it? Although those aren’t as common here and still leave the issue of water heating so perhaps not that relevant.

I suppose there’s also some argument to be made about efficiency loss using a heat pump with cooler night time air temps in winter, but I imagine that overall it’d still work out favourably for the heat pump in a properly set up system.

Oh how I do love a good heat pump chat, can’t wait for the day I can finally move somewhere suitable for getting one installed

matt_drummer

TheElectricCow said:

A valid point about the flow temp, hadn’t considered that part! I would have thought an Air to Air system might manage it? Although those aren’t as common here and still leave the issue of water heating so perhaps not that relevant.

I suppose there’s also some argument to be made about efficiency loss using a heat pump with cooler night time air temps in winter, but I imagine that overall it’d still work out favourably for the heat pump in a properly set up system.

Oh how I do love a good heat pump chat, can’t wait for the day I can finally move somewhere suitable for getting one installed

I have air to air, it will not keep a house warm overnight any more than any other heating, heat loss is all that matters.

The efficiency of any heat pump depends on how much work it is being asked to do, if the inside needs to maintain a temperature, then the colder it is outside, the more work it has to do as the temperature difference is higher and the heat loss from the home is more.

Efficiency of 300% is the least I would be happy with over a year, sometimes it will be better, sometimes a little worse, hopefully more than 300%

It is called the SCOP (seasonal coefficient of performance)

At times it's possible for a heat pump of these types to be more than 500% efficient.

Hopefully, over time, some of the green levies applied to electricity will be moved to gas, it may be difficult with gas as expensive as it has been but I feel it will really help fuel the change.

TheElectricCow

matt_drummer said:

TheElectricCow said:

A valid point about the flow temp, hadn’t considered that part! I would have thought an Air to Air system might manage it? Although those aren’t as common here and still leave the issue of water heating so perhaps not that relevant.

I suppose there’s also some argument to be made about efficiency loss using a heat pump with cooler night time air temps in winter, but I imagine that overall it’d still work out favourably for the heat pump in a properly set up system.

Oh how I do love a good heat pump chat, can’t wait for the day I can finally move somewhere suitable for getting one installed

I have air to air, it will not keep a house warm overnight any more than any other heating, heat loss is all that matters.

The efficiency of any heat pump depends on how much work it is being asked to do, if the inside needs to maintain a temperature, then the colder it is outside, the more work it has to do as the temperature difference is higher and the heat loss from the home is more.

Efficiency of 300% is the least I would be happy with over a year, sometimes it will be better, sometimes a little worse, hopefully more than 300%

It is called the SCOP (seasonal coefficient of performance)

At times it's possible for a heat pump of these types to be more than 500% efficient.

Hopefully, over time, some of the green levies applied to electricity will be moved to gas, it may be difficult with gas as expensive as it has been but I feel it will really help fuel the change.

Perhaps I’m all to used to the low levels of heat loss in my fairly small well insulated apartment, where a few hours of thorough heating would keep the place noticeably warm for the next 2-3 days unless intentionally cooled (MVHR is a huge help here too, eliminating any damp or mould concerns without having to open windows). Admittedly I can’t say I’ve got a proper point of reference for the heat losses in a full sized house but naturally it makes sense that they’d scale up a lot more, especially if not attached to warm neighbours.

Eventually I can see gas becoming more expensive as we gradually see it start to see less people relying on it and greener energy solutions become a closer reality, probably not for some years yet though. Long term it’s certainly looking like heat pumps will be the way to go, particularly as home generation and storage (hopefully) become more affordable options.

matt_drummer

Our house is very well insulated and has a high epc rating.

It is a four bedroom detached house and our heat loss is 6.8 Kw including the 14 m2 conservatory (that we can isolate)

But it still loses heat and if I want to maintain the temperature then we need to add heat from somewhere.

For me, an air source heat pump will be the most efficient, cleanest and cheapest way to do this.