Daikin Multi+ Split A2A Heat Pump = Heating, Cooling and Hot Water!

tfhnota

So the A2A grant is sort of out-dated by tech before it is actually available as that Samsung will get the A2W grant presumably but should get both.

JKenH

I hope you will forgive me butting in here but I have only just noticed this thread as a result of a link posted today on the G&E thread. B6 agreement I don’t post on that thread but wanted to contribute to the discussion about hybrid systems. I recently added a multi split A2A system to expand my existing A2A installation. FWIW the cost of installing the 3 way multi split (2x2kW and 1x2.5kW serviced by a 6kW external unit) was approximately £4000. I also have a 3.5kW A2A unit. If I had been starting from scratch I imagine the total cost of a 4 way system would have been around £5,000 but the pipe runs might still mean I would still need 2 outdoor units so perhaps nearer £6,000 in reality.

I am optimistic that this A2A system will provide most of my heating needs, but perhaps not all, as during the recent heat waves it has coped very well with cooling most of the house. I have an existing oil boiler which runs a wet conventional CH system and heats the water in one of our two hot water cylinders. Because of the length of the pipe runs that would be needed to reach it our second HW cylinder is heated purely by immersion heater.

The extension of my A2A system was prompted by the high prices for oil (short term blip hopefully) and the expansion of my PV system with an additional 5kW of south facing panels and a Tesla Powerwall (thanks @Screwdriva). I am also lucky enough to be currently on Octopus Go and paying just 4.99p/kWh off peak. Oil prices are currently about 80p/litre so after system losses about twice the cost of heating water by electricity so even the cylinder that is plumbed in to the OFCH boiler is currently being heated by overnight cheap electricity. [As a retired couple our hot water demand is not that high, perhaps 4-5kWh/day so the premium I currently pay for using an immersion heater is about 15p/day (23p immersion vs, say, 8p heat pump). Even if my cheap rate were to double in price the premium is only 30p per day or say £100/year so I would find it hard to justify spending, say, £2,000 on a fancy heat pump tank.]

I did out of curiosity, enquire of Octopus online about a Cosy A2W heat pump but the size of my house/system resulted in a “computer says no” response. Realistically, I could imagine it costing £15,000. This wasn’t really a serious enquiry as I imagine with 2 existing outside A2A units planning permission would be required and I am not sure I want to put all my eggs in the one heat pump basket.

As @michaels suggested on the G&E thread addition of a supplementary A2A heat pump system to an existing fossil fuel system could be quite an attractive option for many people who have reservations about going fully down the heat pump route and it does have two additional benefits. The first is it provides Aircon in summer, which has been a boon, especially for sleeping.

Secondly, and the real driver for me, is that it enables me to exploit whichever is the cheaper fuel at the time.

Heating in the shoulder months could be covered by a combination of my extended solar and battery at an opportunity cost of 12p/kWh in foregone solar export.

Retaining my oil based system does give me the option of my cheap rate overnight tariff fines or,if I run out of cheap rate electricity or solar, using my oil boiler again. I could even risk switching back to Agile and exploiting the very cheap rates when available to run solely on electricity then using oil for heating when electricity rates are high. Anyone retaining their has boiler could do likewise. I do anticipate volatility in energy prices for some time to come and having the flexibility to switch between fuel sources for whole house heating is very attractive. (Perhaps, less likely but not entirely unlikely, is the fact that either heat pump or boiler could break down and as a retired couple having a back up is appealing. With my PW3 during a prolonged electricity interruption I could keep warm using the oil boiler.)

I know people are keen to ditch their boilers but unless you really need the space I believe there are good arguments for hanging on to your old CH system while taking advantage of the savings from an A2A system. I acknowledge that with gas there will be a standing charge and service costs so maybe the argument is not so strong as for those of us who burn oil).

Netexporter

Alternatively, if you live in a rural area, install a woodburning stove for emergency heating in case of a prolonged power cut. OK it won't give you DHW but the choice between ponging a bit and freezing is fairly easy to make. People living in cities rarely get power cuts, so back-up probably not required.