Heat loss from hot water tank - calculating cost

[LocoBlade]

I'm currently mulling over unvented hot water tanks and although they all list energy ratings and KWh loss per day, I'm unsure how that relates to actual running costs to determine if a more expensive but better insulated/lower heat loss tank is worth the extra spend or not.

My gut feeling is that as the tanks I'm looking at are rated at between 1.2KWh and 2.4KWh heat loss per 24 hours and a KWh of gas is only about 4p, even if the boiler etc was only 50% efficient at converting that gas energy to water tank heat (Im guessing it's higher?) you're still only looking at about 10p/day or £35/year more to compensate for the heat loss so you'd be waiting forever to get your money back on something like an A rated OSO that costs £600 more up front to buy. Am I missing anything?

[LocoBlade]

Jambo85 said:

The other thing to remember is this heat loss is into your house, so it’s heating that you don’t need to add. Only two months of the year that’s not welcome up here

For us the tank will be in what's currently an outside toilet built into the side of the house where the boiler also is, so it won't really leak its heat into the house and will also be unheated in a lower ambient temperature which could cause more losses, which is one of the reasons I was considering the best insulated tank I could find.

[LocoBlade]

ST12AT said:

The heat loss per day is negligible between cylinders in a domestic environment.

Coil rating/recovery time is more important.

Joule make excellent cylinders if you are wanting to compare another brand to the OSO one.

Cheers, any opinion on what the Heatrae Sadia ones from Plumbnation etc are like, one of our plumbers I'm waiting on a quote from fits those, made by the same company as Megaflow? another mentioned RM Cylinders which I think are branded as Joule?

I'm looking to use Genius controls which can utilise a water temperature sensor on the tank, do these tanks usually come with a pocket/hole in the inslation to fit a probe as I've seen mention of people with Megaflows moaning because theirs don't?

Edited by LocoBlade on Wednesday 28th October 09:03

[LocoBlade]

dhutch said:

As said, modern cylinders are very good. I did a table of a few well known brands around the 200-300l mark which is on a few threads around here.

Joule are as said well known for reasonable prices, the Worcester ones get good press but are shorter and wider which is good for losses but wouldn't fit in my cupboard and where dear. I read too many stories of Megaflow internal baffles breaking up, so went with a OSO which a year in appears good.

Thanks, will have a look for that.

[LocoBlade]

ST12AT said:

If you are anywhere in the South East I’d accept that challenge....

I'm in the process of getting a couple of quotes now for a new system boiler, tank and possibly accumlator installed. If you cover NE Hants/Surrey border and have free slots in the diary this side of Christmas I don't suppose you fancy giving me a quote do you?