Electric heater vs oil filled - consumption sums

dilby · 25 November 2021 at 1:46PM

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

ChaunceyGardiner · 25 November 2021 at 1:57PM

An oil-filled heater might provide a slightly more 'even' heat, but it will be no more energy efficient than any other type of electric heater.

Astria · 25 November 2021 at 2:26PM

Oil filled radiator will stay warm for a while when it's off, but it'll also take longer to go from cold to warm, so the end result will be the same.

If you can use the central heating from the house then that is the best solution as I assume it's powered by gas. During the winter months however I'd keep some circulation going even when you are not in the office to prevent the pipes getting too cold and freezing.

It may be best if you go for a electric heater which heats you rather than the air around you, such as halogen heaters.

Rivers_mum · 25 November 2021 at 2:48PM

I’ve got friends who have bought calor gas heaters on the pay in advance peace of mind basis but I’ve no idea how it works out on a value basis and of course you have the heater and bottle to buy.

matelodave · 25 November 2021 at 3:08PM

A 15kg cylinder refill of Calor gas is about £42 at the moment and that will give you around 15 x 14kwh = 210kwh = 20p/kwh which is slightly cheaper than the latest electricity cap tariff.

However you get lots of condensation and need a lot of ventilation and they are pretty big and heavy..

Smaller cylinders cost even more per kwh. (a 7kg cylinder is nearly 27p/kwh) You also have the aggro of swapping cylinders when they are empty and you really need two to ensure continuity of supply.

I use Calor gas in my caravan but only for cooking, it's too expensive to use for long term heating

wittynamegoeshere · 25 November 2021 at 3:21PM

Don't use a gas heater in a confined area, you might die. Seriously.

The oil in an "oil-filled" radiator does not have any magical properties, it's not made out of snakes for example. All it does is transmits heat from a metal electric heating element to the outside of the radiator from where it can escape into the air. It doesn't mysteriously magnify the heat.

If you were to extend the gas heating then you'd probably lose a lot of heat on the way and would just be throwing heat from another source away.

Your choices are either to carry on paying lots to heat a botched building and just accept it, or take it apart and rebuild it properly.

What are the inner walls made of? It may make sense to just gut it from the inside, put some slab insulation in then a new inner surface. Some research required though, you'll need a vapour membrane and probably an air gap, don't replace one botch with another.

Rodders53 · 25 November 2021 at 3:35PM

Energy needed to heat this outbuilding will be identical whatever method you use.

Electric heaters convert 100% of the energy in to heat... whatever type is used (fan, radiant, oil-filled). Improving insulation and draught proofing may reduce the building heat loss.

LPG Gas heater generate a lot of water during combustion unless it is a room sealed device (more expensive) so probably best avoided?
In any case Calor LPG 13kg (@ 14kWh/kg) cylinder refills are currently £40. So I calculate that to be 22 pence per kWh. Calor 15kg butane (used in domestic heaters @ 13.7 kWh/kg) is £46.50 and thus 22.6p per kWh.
Electricity is likely to be a similar enough price to make the hassle of getting cylinder refills a non-starter.

Swipe · 25 November 2021 at 4:12PM

There's also the cheaper option of not using the office during the cold winter months

QrizB · 25 November 2021 at 6:38PM

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.

As others have said, a panel heater or an oil-filled heater will both take the same amount of electricity to keep your home office at the same temperature.

However, I notice you say "I need to keep it running often throughout the day". Does the heater have a thermostat? If so, it will only run as much as it needs to to keep your office warm, and it's unlikely to be running at full rated output continuously. Do you have any way to measure or estimate how much electricity it actually uses during the day?

If you don't mind people thinking you're odd, you might consider a heated seat pad. I've recently aded one to my WFH chair and it does a good job of keeping me warm when I'm the only one in the house (wife out, kids at school) and running the GCH is overkill. At around 20 watts it's not going to break the bank either.

Reed_Richards · 25 November 2021 at 9:30PM

The way to heat a room electrically with the lowest running costs is to use an air-to-air heat pump. This is basically an air conditioning unit that can be run in heating mode. The problem with this is the installation cost and how long the pay-back time would be until your running cost savings paid for the installation. If you are running your 1.25 kW heater for 8 hours a day that's 10 kWh per day which is going to cost you over £2 per day. You might be able to cut that down to 50p per day, saving £1.50 per cold day. So that might be, say, £200 per year saved. I'm guessing the air conditioning unit might coat £600 to £1000 installed, which would be 3 to 5 years payback. But these are all very rough estimates, you would need to do much more detailed calculations.

matelodave · 26 November 2021 at 11:38AM

As said above, summat like this would be a good option as not only does it heat in the winter but it will cool in the summer. Air-air heatpumps generally have a better SCoP than air-water. This one for instance has an SCoP of 4 which means that it will produce 4kw of heat from 1kw of leccy.

Korel 12000 BTU WIFI Smart A++ easy-fit DC Inverter Wall Split Air Conditioner with Heat Pump INV12TWiFi | Appliances Direct.

Other makes and sizes are available

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Electric heater vs oil filled - consumption sums

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