Mixergy with heat pump - Worth it? 13 October 2022 at 11:32AM edited 13 October 2022 at 11:33AM in Green & ethical MoneySaving 5 replies 178 views

waqasahmed

I don't have a tank atm, and my plan of action for the house is:

Solar PV + batteries
Then get an MVHR 
Upsize my radiators 
Then buy an ASHP and ditch gas entirely. 

They say that the COP is improved by 5-10% but let's say that your COP is the UK average of 2.8. Would a COP of 3.08 really be worth it, if this tank probably costs a few grand? 

shinytop

waqasahmed said:

I don't have a tank atm, and my plan of action for the house is:

Solar PV + batteries
Then get an MVHR 
Upsize my radiators 
Then buy an ASHP and ditch gas entirely. 

They say that the COP is improved by 5-10% but let's say that your COP is the UK average of 2.8. Would a COP of 3.08 really be worth it, if this tank probably costs a few grand? 

Depends how much hot water you use I suppose.  And I don't know much about Mixergy tanks but if they involve heating the water in lots of small bursts then that's not going to work well with an ASHP.  Every time the water heats, the ASHP will stop, which is likely to make it less efficient. 

waqasahmed

shinytop said:

waqasahmed said:

I don't have a tank atm, and my plan of action for the house is:

Solar PV + batteries
Then get an MVHR 
Upsize my radiators 
Then buy an ASHP and ditch gas entirely. 

They say that the COP is improved by 5-10% but let's say that your COP is the UK average of 2.8. Would a COP of 3.08 really be worth it, if this tank probably costs a few grand? 

Depends how much hot water you use I suppose.  And I don't know much about Mixergy tanks but if they involve heating the water in lots of small bursts then that's not going to work well with an ASHP.  Every time the water heats, the ASHP will stop, which is likely to make it less efficient. 

Apparently they're designed to work with heat pumps? So I doubt that? FWIW, currently my average gas consumption for the day (heating water + heating in general) is around is under 20KwH a day. My shower today was 1.2 kWh for about 5 minutes or so

shinytop

You'll need an ASHP compatible tank anyway so a Mixergy one with the ASHP facility is only going to be a few hundred more, not thousands. 

Screwdriva

Here's a quote I received for a Solar and Heat Pump ready cylinder. Given the terrible aftersales support received from Megaflo/ Baxi, I would definitely have invested in Mixergy if I could do it all again. 

Anyone know if there is a efficiency advantage over Vaillant heat pump hot water cylinders?

Reed_Richards

Looks to me as if a mixenergy tank has some useful features such as being "heat pump ready" - which presumably means it has a suitably large-area coil inside.  And there are some gimmicky features like "voice control".  The only way I can see that it could improve a heat pump COP is to make the water less hot.