Cost of using electricity to heat a living room

[keving]

OK, here's the problem:

When the ambient temperature of my 25 m2 living room (let's say cubic volume = 75 cubic metres) = 14C and I want to increase the temperature to 21C (assume ceiling fans running in winter mode) is it cheaper per hour to :

(A) run the air con (18,000BTU inverter) in heat mode (automatic fan speed) set at 21C, or

(B) run a fan heater with a thermostat set at 21C.

I suspect the answer is A is cheaper than B, but by what % cheaper?

Additional question: if B was an electric oil filled radiator rather than a fan heater, how would this affect your answer?

[keving]

Yep, Devil's the man!

[J B]

I'm not devil, but in simple electric heating terms (NOT Inverter A/C type stuff) then one unit of electricity gives out 1KW of heat whether it's from an oil-filled rad or a fan heater or a single bar electric fire.
OK, maybe the fan uses a little extra energy but it's minimal

Simples

Cue Devil

[keving]

I'm not devil, but in simple electric heating terms (NOT Inverter A/C type stuff) then one unit of electricity gives out 1KW of heat whether it's from an oil-filled rad or a fan heater or a single bar electric fire.
OK, maybe the fan uses a little extra energy but it's minimal

Simples

Cue Devil

I go with you on that one JB .. what I would call "conventional heating" ie fan heaters, oil filled radiators, quartz tube infra red heaters are all in the same ball park with regard cost per hour of heating a given volume of space.

But the real thing is that many people (including myself) are aware that it is very costly to cool a room via a air conditioner, so we apply the same logic to heating a room via a air conditioner. I know the maths work in reverse ... Devil I need you !

[Poppy]

This may help you. We had the new style 24000not Air con unit in the living room which heated the very large room and even the adjacent kitchen very effectively set on 22/23.
We had run out of logs for the fire some 4 weeks ago and did not buy more as we were leaving. Our final bill was 140 Euros which included the air con,immersion heater,cooker,pool pump etc,etc which we thought to be reasonable during such a cold spell when we often had it on through the daytime as well as the evening.

[cyprusgrump]

As has been said...

Any 'resistive' heater, be it an oil filled radiator, fan, convector or any other kind gives you (ignoring losses) a 1:1 ration of heat to power in.

So a 1KW electric heater will give you approximately 1KW of heat output for every unit of electricity it uses.

A split air conditioner is effectively a 'heat pump' - it uses electric motors driving fans and compressors to collect tiny amounts of heat from the atmosphere and concentrate them in your house.

A modern 'inverter' air conditioning unit can give you as much as four times the energy in heat output as it costs to run it. So 1KW of electricity gives you 4KW of heating.

Even the 14 year old unit in my man cave has a heating capacity of 13,500Btu/h but uses only 1,350W of electricity. A ratio of about 3:1

[Devil]

As I've been evoked, nothing really to add. A modern DC inverter aircon will give you up to ~4 kWh of heat for 1 kWh of electricity, but the heat is embedded in the airflow, not in direct convection or radiation.

[keving]

Thanks all. Had my new inverter running on heat mode last night, set at 21C, and the room felt a lot warmer than either using the central heating or a fan heater.

[PaphosAL]

it's a good idea also to set your bedroom A/C mode in Summer to Eco mode, so it's just squeezing the humidity out, but still leaving you with a comfortable nights kip @ 24ºc without sweating, in dry air!

[PaphosAL]

Winter in Cyprus and heating? NOT cheap to use your AirCon in reverse mode! Your leccy bills will be sky HIGH!

Better off getting a Calor Gas heater to warm your abode, but make sure you read the instructions thoroughly, and ALWAYS leave a window ajar (for safe ventilation) but also secure the same window, so that low-life toe rags cannot invade your property!!!

[Pafos]

Winter in Cyprus and heating? NOT cheap to use your AirCon in reverse mode! Your leccy bills will be sky HIGH!

Some are actually more efficient (cheaper/less consumption) to run in heat mode than in cooling mode.

I do agree the new inverter A/C units are much more cost effective to run, and are near silent in operation. One of mine (inverter, good brand) you cannot set a temperature for heating though. It reverts to either 19C if the room is very cold or 23C once the room has warmed in auto mode. It's a very efficient heater though.