That’s right. Inline heater models like the ZIP Inline CEXU which I’d referenced in the other thread Brian linked have pretty smart electronic controls and bring in their heating elements gradually in order to maintain whatever target water temperature they’ve been set to. So most of the time they’ll stay in ‘standby’ mode and even when they’re ‘on’ they won’t be running at full power unless they’re being fed with properly-cold water. During the Summer they could be switched off at the electrical isolator so they’re not even drawing any ‘standby’ power.
There are a few practical considerations to be aware of:
- The CEXU is rated at 8.8kW (though it can be set to a maximum of 6.6kW instead) so it needs to be on a dedicated wiring circuit using suitable cable
- There are some restrictions on the types of ‘appliances’ which can be connected - e.g. I expect a ‘power shower’ with a pump would not be suitable
- The connections are only for 15mm copper pipework and bear in mind the ‘hot’ water would be running through the unit all the time so the flow is bound to be restricted to some extent - which might be problematic if the water pressure isn’t great
- As a consequence, I don’t think it would be reasonable to expect these to perform as ‘whole house’ top-up water heaters - or for filling a bath
But definitely an option to consider in the event the mini store isn’t quite coping in Winter.
[See also this later post which has more detail on experience with the ZIP InLine CEX and its flow rate limitations.]