Electric heater vs oil filled - consumption sums

jbryce

dilby said:

Hi all - not sure if this is a good place to post this but I figured some people might be able to help. I've got a home office that I had recently built, but it's only insulated with rockwool (company didnt offer rigid options like kingspan) and it gets pretty cold as the winter sets in. I've currently got a 1.25kw electric heater on the wall but I'm a bit concerned about heating bills over time, as I need to keep it running often throughout the day as the heat loss seems to be pretty high. I'm going to look at what I can do to help that (a little low on options at the moment) but for the short term I'm trying to do the sums on if the cost of an oil filled radiator would be better but I'm not sure how. If both are the same KW then i cant differentiate as a basic kw/h equation will render same results, but I'm of understanding that the benefit of an oil filled radiator doesn't have to be on as much as the radiator will retain the heat. Is there therefore a way I can work that out, or is it a suck and see situation? I've also look at teeing off the central heating in the house and running an insulated pipe through ground out to the office, but from what I can tell even with the best insulation the heat loss would be too great. Does that sound correct?

Thanks so much

Every electric appliance is 100% efficient at turning electricity into heat. It makes no difference.
The only exception to this rule is heat pumps which have greater than 100% efficiency.

really?

Some interesting comments here.

I'm having similar thoughts regarding using an oil filled or similar heater to warm a c.27-30m2 kitchen living diner/ sunroom where my wife and kids spend the vast majority of the day whilst she is off on maternity.

My very approximate (likely flawed) maths: We have logic c30 gas boiler (output 24kw) that we typically use via a 1 hour boost function with a stat in the hall. The issue is the stat will only knock off when the hall is at a decent temp so the boiler typically stays on for an hour I think. Our house is epc B1

This I believe means that we will use a max of 24kwh of energy per hour of use if its set at 68 degrees that's 85% of capacity so 20.4kwh.

I currently pay 11.36 per kwh of gas so that's c£2.30 for every hour of use (weather dependent etc).

A £100, 2kw oil filled electric radiator uses c. 35p an hour at peak I've read (depending of tariff etc) and can easily heat the room I'm talking about.

I think this means we could save c. £2 every time we use it paying for itself after 50 uses or at 2 or 3 times a day within a month.
I also very much like the look of the air-conditioner with heat pump and have found one for c.£500 supply only which could also pay for itself within a few months at the gas prices we'll see this winter.

I'm going to dust off a spreadsheet tomorrow and have a proper look at this but was just interested in any thoughts or what you guys in the MSE recommend and are doing

facade

really? said:

Some interesting comments here.

I'm having similar thoughts regarding using an oil filled or similar heater to warm a c.27-30m2 kitchen living diner/ sunroom where my wife and kids spend the vast majority of the day whilst she is off on maternity.

My very approximate (likely flawed) maths: We have logic c30 gas boiler (output 24kw) that we typically use via a 1 hour boost function with a stat in the hall. The issue is the stat will only knock off when the hall is at a decent temp so the boiler typically stays on for an hour I think. Our house is epc B1

This I believe means that we will use a max of 24kwh of energy per hour of use if its set at 68 degrees that's 85% of capacity so 20.4kwh.

I currently pay 11.36 per kwh of gas so that's c£2.30 for every hour of use (weather dependent etc).

A £100, 2kw oil filled electric radiator uses c. 35p an hour at peak I've read (depending of tariff etc) and can easily heat the room I'm talking about.

I think this means we could save c. £2 every time we use it paying for itself after 50 uses or at 2 or 3 times a day within a month.
I also very much like the look of the air-conditioner with heat pump and have found one for c.£500 supply only which could also pay for itself within a few months at the gas prices we'll see this winter.

I'm going to dust off a spreadsheet tomorrow and have a proper look at this but was just interested in any thoughts or what you guys in the MSE recommend and are doing

You'd be better off moving the thermostat to the room you want to heat, then put TRV's on the other radiators, and turn them down to "cool" and keep the doors shut.  You might need to look at balancing the radiators as well.

QrizB

really? said:

My very approximate (likely flawed) maths: We have logic c30 gas boiler (output 24kw)

That's a combi boiler. It will only put out 24kW when you're using it to eg. fill a bath or run a shower.

The amount of heat it puts into your house will be limited by the capacity of your emitters (radiators, towel rails, UFH etc). For a typical 3-bed semi you might only have 10kW-worth of radiators. (If you're enough of a geek you can go around your house, measure your rads then look up typical heat outputs for each one.)

I'm having similar thoughts regarding using an oil filled or similar heater to warm a c.27-30m2 kitchen living diner/ sunroom where my wife and kids spend the vast majority of the day whilst she is off on maternity.

What size is the radiator in this room? That will give a rough indication of the heat demand.

I currently pay 11.36 per kwh of gas so that's c£2.30 for every hour of use (weather dependent etc).

£1.14 if you've got 10kW of radiators, and for price that you're heating the entire house.

A £100, 2kw oil filled electric radiator uses c. 35p an hour at peak I've read (depending of tariff etc) and can easily heat the room I'm talking about.

I don't know what electricity tariff you're on but I would guess that, if you're paying 11.36p per kWh for gas, you've taken out a fix in the past 6 months and are probably paying around 35-45p/kWh for electricity. At that tariff a 2kW electric heater will cost 70-90p/hr.

I think this means we could save c. £2 every time we use it paying for itself after 50 uses or at 2 or 3 times a day within a month.

This sounds very unlikely in practice. On the revised numbers above, your saving is, at best, 44p per use. I suspect it will prove to be less.

I also very much like the look of the air-conditioner with heat pump and have found one for c.£500 supply only which could also pay for itself within a few months at the gas prices we'll see this winter.

Is this a mini-split, a monobloc or a mobile? (Examples for illustration only, not recommendations.)

• Unless you are (or know) a FGAS fitter, by law you will need to employ one to fit a split heat pump.
• There are monobloc ones that don't need an FGAS fitter but these need two big holes in the wall and are relatively noisy as all the mechanical parts are inside the house, not outside.
• Mobiles are fine for occasional use but personally the noise would drive me up the wall if I used one all winter.
  

really?

QrizB said:

really? said:

My very approximate (likely flawed) maths: We have logic c30 gas boiler (output 24kw)

That's a combi boiler. It will only put out 24kW when you're using it to eg. fill a bath or run a shower.

The amount of heat it puts into your house will be limited by the capacity of your emitters (radiators, towel rails, UFH etc). For a typical 3-bed semi you might only have 10kW-worth of radiators. (If you're enough of a geek you can go around your house, measure your rads then look up typical heat outputs for each one.)

I'm having similar thoughts regarding using an oil filled or similar heater to warm a c.27-30m2 kitchen living diner/ sunroom where my wife and kids spend the vast majority of the day whilst she is off on maternity.

What size is the radiator in this room? That will give a rough indication of the heat demand.

I currently pay 11.36 per kwh of gas so that's c£2.30 for every hour of use (weather dependent etc).

£1.14 if you've got 10kW of radiators, and for price that you're heating the entire house.

A £100, 2kw oil filled electric radiator uses c. 35p an hour at peak I've read (depending of tariff etc) and can easily heat the room I'm talking about.

I don't know what electricity tariff you're on but I would guess that, if you're paying 11.36p per kWh for gas, you've taken out a fix in the past 6 months and are probably paying around 35-45p/kWh for electricity. At that tariff a 2kW electric heater will cost 70-90p/hr.

I think this means we could save c. £2 every time we use it paying for itself after 50 uses or at 2 or 3 times a day within a month.

This sounds very unlikely in practice. On the revised numbers above, your saving is, at best, 44p per use. I suspect it will prove to be less.

I also very much like the look of the air-conditioner with heat pump and have found one for c.£500 supply only which could also pay for itself within a few months at the gas prices we'll see this winter.

Is this a mini-split, a monobloc or a mobile? (Examples for illustration only, not recommendations.)

• Unless you are (or know) a FGAS fitter, by law you will need to employ one to fit a split heat pump.
• There are monobloc ones that don't need an FGAS fitter but these need two big holes in the wall and are relatively noisy as all the mechanical parts are inside the house, not outside.
• Mobiles are fine for occasional use but personally the noise would drive me up the wall if I used one all winter.
  

What size is the radiator in the room?

There are 2 one is c. 2.6 to 2.8 long by maybe .4-500 high and the other something like 1.5 x .600/700. There are patio doors facing south and a sunroom with south west and north facing windows and a bay window that also faces north.

I popped some ball park dimensions into calc and it spat out 1.791 as a kitchen and 2.985 Watts as a lounge. I assume that is what is required per hour? So somewhere in between the two of those figures.

Re: tariffs I've checked and my electric is 28.23p and gas is as above not fixed so I'm sure it will jump.

Yes I believe the one I'm looking at will need FGAS fitter but would happily pay it if it paid for itself this winter. It would be a decent addition to the sunroom which despite being double glazed gets too warm in the winter and too cold in the summer. 

Thanks for taking the time to reply and challenging my back of napkin numbers. I'm thinking that an oil filled may across the winter eventually pay for itself on a like for like comparison e.g. assuming that the electric heater is on for the same duration as the gas boiler would have been. But I have a suspicion that the electric heater would be on for less time given the local thermostat. It should all being well knock off when the kitchen is at a comfortable temp not when the hall is.

I'd intend to keep using the gas to heat the whole house say 30mins in the morning and an hour in the eve only using the electric throughout the day.

Ah well I'm significantly less sure of all this now.

I remember when the gas bill in my old 90m2 semi was £327 for the year, that won't get us through a month this winter 😃

really?

facade said:

really? said:

Some interesting comments here.

I'm having similar thoughts regarding using an oil filled or similar heater to warm a c.27-30m2 kitchen living diner/ sunroom where my wife and kids spend the vast majority of the day whilst she is off on maternity.

My very approximate (likely flawed) maths: We have logic c30 gas boiler (output 24kw) that we typically use via a 1 hour boost function with a stat in the hall. The issue is the stat will only knock off when the hall is at a decent temp so the boiler typically stays on for an hour I think. Our house is epc B1

This I believe means that we will use a max of 24kwh of energy per hour of use if its set at 68 degrees that's 85% of capacity so 20.4kwh.

I currently pay 11.36 per kwh of gas so that's c£2.30 for every hour of use (weather dependent etc).

A £100, 2kw oil filled electric radiator uses c. 35p an hour at peak I've read (depending of tariff etc) and can easily heat the room I'm talking about.

I think this means we could save c. £2 every time we use it paying for itself after 50 uses or at 2 or 3 times a day within a month.
I also very much like the look of the air-conditioner with heat pump and have found one for c.£500 supply only which could also pay for itself within a few months at the gas prices we'll see this winter.

I'm going to dust off a spreadsheet tomorrow and have a proper look at this but was just interested in any thoughts or what you guys in the MSE recommend and are doing

You'd be better off moving the thermostat to the room you want to heat, then put TRV's on the other radiators, and turn them down to "cool" and keep the doors shut.  You might need to look at balancing the radiators as well.

Sounds like a bit of a job moving the stat tbf. I Wonder if a smart thermostat could be the way forward here? 

OK yeah there could be something in that as the main living room is uncomfortably hot when the kitchen living diner is just at a reasonable temperature