A year ago when we replaced our gas boiler we also replaced the hot water cylinder. There were various reasons for that:

1. I wanted to use an immersion heater to maximise use of generated PV electricity
2. The old cylinder didn’t have an immersion heater and we were advised against trying to open the portal on a 40 year old cylinder.
3. Ideally a cylinder for such heating would have a low down entry portal for the immersion heater so that the whole cylinder volume is heated – whereas our portal was in the top.
4. Our old cylinder was uninsulated, although it did have an insulating jacket.
5. Given that we’re potentially heating day’s hot water up-front with solar PV rather than on demand by gas then we might reasonably want a larger stored volume.

We ended up with the 210 litre Gledhill tank illustrated for which we had to sacrifice an airing cupboard shelf as it’s that much taller than the old cylinder. Both immersion heater and thermostat for the gas are at similar height towards the bottom. The smaller cylinder at the side is to manage expansion of the water in the absence of an expansion tank in the loft.

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