If your insulation isn't very good, it's just not worth it financially and you would also need a much larger system. The bulk of use for gas would be in the winter, which negates the point of a lower CO2 system. Plus on hybrid you don't get the RHI without monitoring, non hybrid you just get it paid.

@batalto, the RHI is a valid point. I will say that our EPC when we purchased our house was a D (67). Insulation, as I've said a few times, is good, not excellent with a few rooms not coming to temperature when it gets really cold. As it transpires, there were a few issues that were responsible for that. Amongst them was insufficient flow to the north end of the house and undersized rads. Now that we've addressed this (with back-to-back sub-zero evening) things seem to be a lot better and I think our insulation is enough to get and keep the house at temperature now.

We still have our oil boiler connected, which I have to say hardly ever comes on – it's nice to have as a back up, but nothing more than that at this stage. 

agree - lets put RHI aside for a while and think about the principle - we easily install air conditioners to cool the house without giving insulation a thought, even the experts do not make a fuss about insulation - it works, cools the house, does not struggle etc.

During winters we just run it opposite - it moves heat from outside to inside - the temperature delta up to 15-18c could be the same - doesn't matter which direction, if you all agree then why do we have a different approach when it comes to use the same principle for heating?

@neilsondhi, I think the difference would be that AC units are air-to-air, where ASHPs tend to be air-to-water. Having lived in an AC environment for years, you're right, there's no need for insulation because the AC units blast the air, which doesn't really happen with our ASHP system- it's a far more passive heat.

@Derek-m has just put in an air-to-air ASHP, so would be intrigued to hear what kind of heat that generates whether the heating is "instant" as with air conditioning units.

@editor You got me thinking - Air to air or air to water, it's just the media used to transport heat - should that make a difference?

@neilsondhi, I can only speak from experience. In a hot climate, when a room is say 40C, and you turn the AC on (air-to-air), within 5-10 minutes the room gets back to 21C, for example. 

In our house, with our air-to-water system, when a room is at 16C, it'll take hours to get it back to 21C. That's why I'll be super interested to hear @Derek-m experience and thoughts on his air-to-air ASHP.

@editor lets wait for @Derek-m to share his experience - my curiosity is high too.

I have air-to-water system like yours for the house and yes it does take a while till it gets to its target temperature. My Gym (~24 sqm room) has air-to-air ASHP - it is usually fast to get to desired temp. and the walls have no insulation which got me thinking.

Hi Everyone,

I am planning to write a review of the electriQ Air to Air ASHP that I installed recently, after a suitable period of use.

As Neil suggested above, I have indeed gone hybrid.

The way I now operate my heating system is as follows.

The gas boiler provides heating (set at 21C) and hot water during the night. (Used approximately 20kWh of gas from midnight to 08:30).

When I arose this morning at 08:30 I checked to see how much power my solar PV was generating (about 1.5kW at the time), so I switch on the ASHP with a setpoint of 23C. The ASHP I installed is rated at 2.62kW heating capacity (it only draws around 500 to 600 watts), which is more than adequate for our small bungalow when the outside temperature is at 5C and above.

Within approximately 15 minutes the temperature in the hallway and out into the rooms had risen from 20.7C to 21.7C. This had the effect of winding back the temperature controller and hence not firing the gas boiler.

The excess output from the solar PV was initially diverted to the immersion heater to provide hot water at approximately 65C. When the tank was up to temperature the excess was then diverted to a 2kW electric heater in the hallway. This had the effect of winding back the heat output from the ASHP outdoor unit unit it eventually stopped. The fan in the indoor unit continues to run at the slowest of 3 speeds and hence helps distribute the heat energy produced by the electric heater.

At 11:45 the inside temperature is now at 22.7C with an ambient air temperature of 11C. (My wife is happy, the cats are happy and therefore I am happy).

As has been the case over the past few sunny days, the vast majority of energy used during the day comes free of charge from the Sun, we will draw a very small amount of electricity and gas from the grid during this period.

When the Sun starts to set I will switch off the ASHP and the gas boiler will once more fire up to maintain the indoor temperature at 21C.

I am carrying out a number of tests at the moment to see how to improve efficiencies and will write an article in the near future.

If you have any further questions please feel free to ask.

Regards,

Derek.

Hi again,

I forgot to mention why I think there is more emphasis put on insulation with reference to heating rather than cooling. Though I feel it is equally important for cooling.

In the cold of Winter ASHP's are not as efficient, and hence need all the help they can get. It would be the same as running an AC Unit with the windows open.

The other reason I decided to go for an Air to Air ASHP is that it will also provide AC if we have any hot Summer days.

Regards,

Derek..

@NeilSondhi, isn't is just because your A2A unit is heating air locally whereas the A2W heats water remotely ?  Air heats up faster than water and it doesn't have to be pumped around the house.  Also, what's the output of your A2A unit? If it's 2kW or more, that is going to heat your room quite quickly because it'll just blast out hot air at maximum power till it's up to temperature.  The fact that the room has no insulation means it will have to repeat this sooner than if it were insulated.  And maybe its output is high for the size of room. My 42 sqm lounge has a total output from its radiators of about 2.5kW (although accept it will be better insulated). 

@kev-m I have 3kW, it's the one with those fancy inverter technology and it does heat very fast. Nevertheless - going back to basics - leakage of heat no matter summer or winter - (through the walls, windows and doors) should be constant. The capability of the condenser to move heat in either direction (that works as the evaporator) depending on the direction you want the heat to go could be considered to be constant - I thought its better in winters because the evaporator is usually twice or thrice the size. I am no expert and perhaps asking silly questions as it does not make logical sense on why experts say ASHP will not work while the same has no issue when you use to cool the room.

@Derek-m - Can't wait to read you full review. your thought on efficiency got my attention - I thought ASHP are highly efficient up to 5c and it might be better to move to gas boiler below 5c - did I get it wrong?