@old_scientist It did work fine with cosy over the winter, although we have the larger version of your heat pump I only exceeded the battery capacity on about 5 days. I left the battery to do the clever cycling stuff and ran the heat pump as if it were on a flat tariff, wholly blind to the battery.

@papahuhu With 27kWh of battery capacity, I find the luxury of 24/7 heat pump operation and being able to avoid the ups and downs of temperature from trying to ride the peak prices, absolutely invaluable - no smugness intended, even if it is showing in dayglow orange!😉 Toodles.

@toodles 

How much power does your phase changing water heater thingy use in winter?

@papahuhu There are just the two of us and we shower and use cold fill for the washing machine and the dishwasher; however there is the need for hot water at the sinks. Winter consumption is ~4 - 4.5 kWh. During the summer, consumption is ~ 2.5 - 3.0 kWh. The Sunamp Thermino heat loss is stated as no more than 0.75 kWh per day; any ‘loss’ keeps our airing cupboard cosy year round. I should point out that our choice was greatly influenced by the inability to accommodate the MCS required size of DHW tank without enlarging the loft hatch and experiencing heat loss from the tank being in an unheated space. Regards, Toodles.

@toodles That’s economical, about the same as an immersion heater for 90 mins. I was expecting it to chew through an entire battery at least.

@papahuhu Here is a screen grab from Myenergi’s Eddi controller; all of the power supplied to the Sunamp Thermino is via the app whether solar or from grid. The daily consumption for each day so far this month. At this time of year, solar energy provides all power and as this would otherwise realise 12 pence per kWh. with Outgoing Fixed export, I reckon it is very reasonable. Regards, Toodles.

@toodles Difficult to tell at this low resolution, but looks like the heating cycle is about 3-4 hours and about 2-3kW, so I make it very approx about 10kWh, which seems much more in line with what I’d have expected. Even at 10kwh at an heating efficiency of about 90% that’s still good going, you must be quite frugal with the hot water.

@papahuhu As you say, the resolution is there to tax you! No, the total consumption for a heating session is what is indicated by the spikes - not the kW. Therefore in any one day, the Eddi will charge the Sunamp at varying rates up to (if available from the solar source) 3 kW, normally this will complete in about an hour or a little over. If the full 3 kW is available without a halt, then charging is taking less than an hour per day at present. Please see higher res. indication for today.

Regards, Toodles.

At 2 kWh its either breaking the physics of sensible heat or you are a tyrant and forcing your good lady wife to shower with a thimble of tepid water!

Even if it were at 100% efficiency, 2kwh of power will raise the temp of 100kg of water by 17C. I can’t find an actual manufacturers efficiency figure anywhere, they are very coy about it. 

@papahuhu Well all I can say is, it works! Neither of us spend that long in the shower and under present heat wave conditions, I find I turn the shower temperature down somewhat as this is more comfortable. I then have to remember to turn the mixer valve back up for the boss - or else! A little over 2 kWh for a day’s hot water requirements does seem very reasonable but it is genuine! Regards, Toodles.

@toodles We (two of us) are using around double that with a more conventional ASHP feeding 160L DHW cylinder arrangement. On average, the heat pump delivers around 4-4.5kWh of heat into the cylinder during summer, using around 1-1.3kWh of electrical input. Tank target temp is 45C.

Mind you, during this heatwave we've been reheating every second day (with cool showers on day two), and have seen 0.9kWh of electrical input for 5.0kWh heat generated, so a COP of 5.5. Can't complain at two days hot water for 10p 

@old_scientist Indeed not! Toodles.