Air Con in heat mode vs Gel Filled Rads - Cheaper to run?

chrisrawles

Evening all,

Total numb nuts here.  We are electric only 3 bed house running gel filled radiators.  Its no secret that this year the cost is on everyones mind.  

Out lounge are is open plan so not the best to retaining heat.  Therefore the rads are kicking in a lot, especially with the cold temps.  I was wondering if anyone has any experience of running an AC unit in heat mode to heat a room?  

I can't seem to find the info on the AC units to work out the running costs.  Any help would be great!

[Deleted User]

AC should be similar to a heat pump - so likely to be more efficient?

grumbler

It doesn't matter what you fill the radiators with - their efficiency remains the same - 100%. Only storage heaters using cheaper energy at night can make difference.

An AC unit in heating mode is effectively a heat pump, that efficiency is higher than 100% (it produces more kWh of heat than it consumes). It's a separate question whether the heating power of your AC unit is sufficient for heating your room, but you can use some radiators as well if needed.

chris_n

All of the air con (heat pump) spec sheets tell you what the power consumption is while heating,  for something with a 2.5kW output the input will be around 800W. 

chrisrawles

If I've worked this out correctly then the cost of my 2 x radiators in the lounge is around £1 per hour if drawing energy.    I know the lounge does not retain the heat so well due to the open plan design.  So keeping the room at a comfortable temperature is difficult.  Just wondered if a "heat pump" would be a slightly cheaper way?

macman

I doubt that your magic custard-filled rads are only 1.5kW? More likely 3kW each, in which case about £1 per hour each at full power.
If mains gas is available, that is your cheapeast option, by about 350% vs single rate electricity.
Heat pumps work best with u/f heating.

Astria

macman said:

Heat pumps work best with u/f heating.

So do normal gas boilers as they are basically one giant radiator heating the entire surface of a room at once instead of one corner with half of it bleeding out of the wall (if on an outside wall).

mysteryUser

When looking at an AC unit you'll see a SCOP value in the specifications. You want to buy one with the highest number you can find. They are way more efficient than a oil/gel filled radiator, unless you're using a portable one, which cause a positive pressure and push your conditioned air out of the room. 

I just searched online, the cheapest split AC unit I found on a particular site mentions a COP of 4.6. So, for each 1kW of electricity you put in, you get 4.6kW of heat out. (based on their standardised tests, in reality the colder it is outside the less efficient it will be). 

I have a 'through the wall' AC unit in my garden office (has 2 large holes to outside). Mine has a COP of 3.1. On Monday I used a total of 923.43Wh to keep warm for the day in my rather well insulated garden office.