Could you help me understand the graph a bit better - I’ve been suggested a 110L FAT MiniStore by HG and am trying to work out if we can make it work for our family of 2 adults and 2 almost teenage boys 
Is the blue line DHW T the temp of the heat inside the mini store, or the temp of the water coming out of it?
And do you have any concerns about how quickly it reheats - I’m specced a 7KW arotherm so imagine reheats would be a bit faster than what you’ve seen? 
I been thinking that if the output of the mini store is boosted by a instant electric water heater for baths and long showers, why not fix a 2nd mixer to the ministore to heat the “cold” water to say 25c?
This shoukd give the heatpump a nice COP whenever it is failing to keep up with demand and make use of more of the stored heat.
The blue line is the store temperature – on my version of the store it’s measured half way up the tank; on new builds I believe it will be nearer the bottom. Either way, the temperature of the water emerging is the same or hotter.
If people limit their time in the shower to something sensible, certainly less than 10 minutes, and if you can wait ten minutes between showers (depending on exactly how hot you shower – as I showed above you could probably shower for 20 minutes or more at 38°C), you’ll be fine. Teenage boys are notorious for spending very long periods of time in hot showers, but if you get a mini store, perhaps they’ll avoid that habit 
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Thank you!
The spec tables suggest I could get ~16 mins @ 8l/min if I keep the store at 65 in the winter, which feels like plenty with a 10 min recharge each shower (while the faffing in the bathroom happens 
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I guess it’s just the fear of the unknown, we’ve had combi gas boilers for 20 years so any change is a big adjustment.
How have you found your performance related to the HG spec sheets – are they realistic or optimistic in your experience?
Before and during use I have been using @MdeP’s spreadsheet from this blog post (the spreadsheet is linked just above the header “Reflections’“), and found it to be pretty accurate.
I restricted the flow rate with a 8 L/m shower flow restrictor which I put between mixer outlet and the shower hose, and kept using the shower’s original shower head which has spray patterns we like. That was much better than the 8 L/min “eco” shower head I tried.
Super helpful, thank you Dan.
Pretty impressed the thing can recharge from completely cold in an hour. And from the looks of it you’ve got a bath out of a starting point of 70 degrees in the store, and recharged ready for another shower in less than 20 minutes
I have a customised MiniStore 80 (version v1.4), fitted with an immersion at the bottom, so the water volume is around 91 litres.
It is plumbed with a mains cold water feed and PRV more than 2m before the inlet, and the heat source is a vented Y-Plan system with a 15 kW gas boiler.
For running a bath now the routine is to use solar gen to preheat up to 65C if possible, boost the gas boiler for HW for 1 hour with setpoint around 70 C, and start running the bath after around 20 minutes. It is still possible to run the HW tap too fast resulting in a tail off of water temp before the bath is full, so still experimenting with a fill rate that completes in 8-10 minutes.
2 consecutive showers are achieved just from the stored water, normally gradually re-heated by the immersion via a solar diverter up to 57 C.
The routime with the previous 30 year old indirect cyclinder required the gas boiler to be boosted for 2 hours with at least 1 hour for preheating the contents through a small surface area coil (no doubt with limescale build-up on it).
From discussions with Newark before purchase, the taller MiniStores have a larger coil fitted, so they would cope better with a large top/bottom temperature difference (stratification) and of course have more volume to store more energy before depleted. I was limited by headroom in the airing cupboard so could not fit a taller MiniStore without the cupboard becoming unusable for airing the washing.
The thermostat bosses are close to the bottom of the cylinder, so provide early detection of draw off and provide an early start of the heat source to allow for startup and warmup to take place ideally before the store starts to deplete.
