300l or 500l water tank

[Nigel]

Hi,

Another question we are having to replace a leaking hot water tank but we don't know whether to get a 300 or 500 l one.

We have an oil boiler that feeds the tank ( it has no element in it) and we have 5 showers and 1 bath in our bathroom ( we run a small apartment house in the Alps). The plumber says we need a 500 tank , at the moment we have a

300 and never seem to run out of hot water. My question is which would would be the most fuel efficient?

My thoughts are that it seems silly heating up 500 l of water when there is no -one else in the house apart from us just for one bath. The apartment are probably full for about 20 weeks of the year so for the rest it is just our needs.

Any thoughts.

Thanks

Nigel

[Andy Hall]

If 300l was OK, it will be in the future unless use requirements change.

It would be more fuel efficient to use the smaller size.

Another thing that you could do (either cylinder size) is to have a second cylinder thermostat fitted perhaps half way up the cylinder and a manual switch to select which is used. Then when it's your use only, you could heat perhaps half of the cylinder, producing 150l only - a more typical single family requirement.

Above all, it's important in any case for the cylinder and surrounding pipes to be well insulated.

[Lobster]

But the question is whether there's enough hot water for the paying punters for those 20 weeks, and if that mans you need the big tank so be it - it doesn't make any odds that the place is almost empty for the other 32 weeks however much that might irritate. Although from para 2 above it sounds like you're OK for the 20 weeks now?, in which case I can't see why the bigger tank could possiby be justified.

David

[The Natural Philosopher]

300l is more fuel efficient..but a well insulated 500l will beat a poorly insulated 300liter.

Its no great shakes either way. Maybe 30- quid a year difference.