Heat loss from hot water tank - calculating cost
Discussion
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?
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?
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.
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.
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.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?Coil rating/recovery time is more important.
Joule make excellent cylinders if you are wanting to compare another brand to the OSO one.
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
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.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.
LocoBlade said:
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?
From your perspective, as the home owner, it really comes down to which you think is prettiest....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
From an installers point of view there are a few difference, I don’t like Gledhill because of their connections and I prefer individual components rather than the ‘all-in-one’ inlet control valve as it allows me to install how I see fit.
I believe that RM and Joule are linked along with Heatrae Sadia and MegaFlo. I’m installing a Main for a mate today, straight forward enough and a little rushed but it’s a fairly decent cylinder that comes with branded components; Honeywell, Reliance etc.
LocoBlade said:
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 said:
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.
We've got a Range Tribune which, even when freshly heated tp 60C, is barely warm to the touch so their insulation is certainly effective. In our case the heat 'loss' serves an airing cupboard (its probably the pipes and pumps that do most of this though) but in your case you could always add your own (extra) insulation to improve any cylinder even further?paulrockliffe said:
This guy is an artist, it's worth trawling his posts for the installation he posted the other day.
Awfully kind of you to say that, this is just in a mates bungalow which I’m doing for a future favour! Standards and there for a reason though....Just missing the discharge pipe work but all finished.
ST12AT said:
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? ST12AT said:
Sheepshanks said:
Lovely to have the space - would be interesting to see that in our airing cupboard!
If you are anywhere in the South East I’d accept that challenge....
We're planning a house refurb and I'm hoping there's space for the boiler and water cylinder to go into what was the oil tank storage 'room' - set into the side of the house.
The Stelrad cylinder in daughter's room leaks enough heat that I don't have to use the radiator except when very cold.
The Evohome TRV in her room is set to 20C, s the rad is currently off, as the hot water cylinder has it heated to a toasty 22C. This is great right now.
It is less great in the summer, when I am using air conditioning to cool a room heated by my gas. Ridiculous.
Plumbing in this house had already been done when we bought it - why on earth they didn't put the cylinders somewhere more sensible than a bedroom, I do not know. I'd have the damned thing in a garage, to keep the chill off my tools and garden equipment in winter and not have to care about in summer.
The Evohome TRV in her room is set to 20C, s the rad is currently off, as the hot water cylinder has it heated to a toasty 22C. This is great right now.
It is less great in the summer, when I am using air conditioning to cool a room heated by my gas. Ridiculous.
Plumbing in this house had already been done when we bought it - why on earth they didn't put the cylinders somewhere more sensible than a bedroom, I do not know. I'd have the damned thing in a garage, to keep the chill off my tools and garden equipment in winter and not have to care about in summer.
Edited by Harry Flashman on Wednesday 28th October 22:20
LocoBlade said:
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?
I usually stick to around 2 hours drive max from home and I will probably be an expensive option compared to a local installer. I do know some guys your way but drop me a message and we can have a chat. Gassing Station | Homes, Gardens and DIY | Top of Page | What's New | My Stuff