This is the point though isn't it, being able to justify the running cost of hot water in relation to the profit being made.
Granted, I wouldn't want to spend a couple of grand on a hot water system, but that's because I'm not in a position to justify such a spend with everything else going on in my life. However, if these circumstances were different, then perhaps I would. Its save and you have the option to run it or not, being job specific.
I wouldn't use the gas option, just for the variable things that could change an explosion, which is more realistic.
I've gone the immersion heater route, lol which is well documented on here (for ones to search, if they have any questions, I'm sure it's been covered). The cost is very small, if you alter your tariff etc, as I have done so. (Again previously mentioned) so it can be a cheap way of using hot water and if trying to justify a small expense, then you are even a tight fisted Yorkshire or a Scot 😁