We opted for this Sunamp design as we just don’t have a suitable space anywhere in the house for a conventional DHW tank of the capacity required by the MCS, and I didn’t much fancy enlarging the loft hatch to fit a tank up there.

This siting would have required all the attendant strengthening work to fit a 250-litre tank that bristles with pipes, sensors and pumps. Thus, we avoided any possible source of noisy motors too! (Not to mention the additional wiring and pipework!) We would also have lost the low-level heat source that we regard as always useful heat in the airing cupboard (which is too small to accommodate a conventional 250-litre tank).

There is an LED panel on the front face of the Sunamp Thermino, providing indications of Power Connected and status of charge. Though very granular, three LEDs indicate full charge, half charge and low charge level. In addition, one LED indicates when the unit is charging.

Our unit sits sideways in the airing cupboard, as the depth of the unit dictated this orientation; the LED display is still viewable sideways without much of a problem, though there is very little need to consult it anyway. We are able to monitor consumption via the Myenergi app, where we set our preferences for charging.

The unit is VERY HEAVY, and the installers had three attempts with progressively more powerful methods of stair-climbing sack trucks to take the unit upstairs! The unit sits over two floor joists, and the load is spread by sitting on two 25mm thick boards as a sandwich.

During installation, the top cover is removed, and several layers of vacuum foam insulation are lifted out to access the pipework. The connections to the water supply and hot water feed are made with solderless swivelling joints that may be set to exit to pipes on the left, rear or right of the cabinet.

On the day the old water tank was removed, we were only without hot water for a few hours while the existing pipework was modified, the Thermino placed, and the pipes and wiring connected. Within 30 minutes of powering up via the Eddi, we had hot water on tap again – there are comparisons with a combi gas boiler in that sense.

Now as to the working – well… it just works. Powered via a Myenergi Eddi, that once set, will provide either PV or grid power as required. The unit is ventless and silent in operation, has no pumps, and heats the cold water as it progresses through a few metres of internal pipework that is surrounded by the Phase Change Material storing the heat. It then exits through the hot outlet and goes straight to a tempering valve for safety.

Expected life? As yet unknown, but tested to the equivalent of 20 years and still good, I’m told. I did hear of a failed unit once, and Sunamp replaced the whole system for the owner without a quibble.

I considered several models but opted for the ePV version, as the one that runs from a heat pump input requires a high-temperature heat pump plus electrical ‘top-up’ to ensure the required minimum temperature. There is also a version for thermal solar panel heating in the range. Please see the website link, which provides dimensions, weights, capacities, and the various models available to match different energy sources.

The Sunamp model we have loses less than 0.75 kW of heat in 24 hours, and what is lost is made good use of as it sits on the floor in the airing cupboard. The total heat loss in the whole heating system is less than when we had a gas boiler and 99-litre DHW tank in there, so the airing cupboard is just a little cooler than it used to be. Our system has a 210-litre capacity, so it isn’t imperative that it is charged every day just for the two of us – we could (and have) left it for 2-3 days and still had sufficient hot water as and when it’s required. Currently, our daily charge consumes ~3kWh, but will rise to about ~4-4.5 kWh in mid-winter. I think a full charge for our unit capacity is ~11.5 kWh.

Would I recommend the system? Absolutely, every time!