Long time lurker but have a pretty good knowledge of ASHP now. I am pretty close to confirming final details of my installation, but I have a 600x550x2200 cupboard for the internal gubbins, hence space is TIGHT and installation companies have questioned what is possible!
I wondered whether there was somebody in this group who had more details about the HG Mini Store Running Cost and COP (I can probably fit the largest 110L version). Given its design, I guess the following are true:
1) The heatpump needs to maintain the higher temperature while drawing water, so whilst you might normally have a cylinder running from 15 up to 45 when refilling an empty cylinder, the mini store can only be fed by 45 degree water for it to work, so reducing potential COP.
2) Rather than being able to draw down the whole tank before refilling you need to re-heat immediately or the water rapidly becomes unusable, even for the larger tank... hence further reducing COP due to cycling. Though perhaps there is enough thermal mass that the temperature doesnt drop that much... (or use a higher store temp which exaggerates 1+2.
3) The heatpump needs to run the when there is demand (rather than offpeak) hence the electricity might also be more expensive than on a normal cylinder.
4) It is smaller so has lower heat losses and doesnt need an expansion vessel (or perhaps just a smaller one....?)
5) Given it doesnt store water very long you dont need to run a high temp legionella cycle weekly....
No idea where this nets out at, in terms of money and efficiency, and possibly depends on your usage of it, but was curious if anybody had any other thoughts, or more detailed numbers!?
Thanks very much
