Radiator - higher BTU = more running cost?

cgray25

I need to replace a couple of radiators and have been shopping around but I've noticed that some like for like radiators will have a significantly higher BTU rate than others (e.g. comparing two same-sized K1 type rads, 1 is rated 500 BTUs higher than the other).

Both can be had for the same price so I was just wondering if the higher BTU one will cost more to run or is it just more efficient by design?

1984ReturnsForReal_2

You need to calculate the BTU rating for the room it is going into to choose what the BTU radiator is you need to be able to heat the room.

Dont buy higher than you need & dont buy lower.

Make sure you use a BTU calculator that ask what the floor is made out of & whether there are external walls.

ormus

if you use the higher BTU rated rad to its max, then it will cost more to operate.
ie
you can get more heat out of it, hence more fuel used, so your running cost increase obviously.
nothing is free in this life.

efficiency ratings per item/product/boiler/engine/machine, is a very different thing.

TimBuckTeeth

If you have a thermostatic control then a higher BTU radiator will heat the room up quicker, but unless you have the room warmer than before it shouldn't use more energy overall. Probably best to use similar to the old radiator if everything was fine, or depending on the boiler maybe could get slower heating in other rooms.

27col

Nothing is free as ormus says. However, you do not need to run the rad at full output all the time. At this time of year, with the temperatures as they are, you can turn the rad up a bit if needed. If it has a thermostatically controlled valve it will look after itself. It will only use more fuel if you have the room at a higher temperature. If you have the room at the same temperature as before then the heating cost will be the same as it was before.

cgray25

Thanks for all the replies

Yes, I'd realised I can fit a TRV and run them at a lower setting as required, I'd also already used a BTU calculator - my question was really relating to efficiency and whether the possibility of a 'free lunch' lied there in. Sorry if I wasn't being specific enough though - I'd read some descriptions that indicated that they can output more heat from less water so, comparing the 2 like-for-like radiators, I'd like to know where the extra 500BTUs comes from? Is it more efficient or am I just paying to have more heated water passing through them?

Tucker

I've tried the btu calcs numerous times and always find they give widely different results.

When I extended, they varied by about 8000 btu's!

Unless anyone knows one that's trustworthy, in my book they are next to useless.

I bought the biggest, highest btu I could fit in and it's been great, as it's a big through room and an open staircase, so there's no warm or cold spots.

TimBuckTeeth

cgray25 wrote: »

..... I'd read some descriptions that indicated that they can output more heat from less water so, comparing the 2 like-for-like radiators, I'd like to know where the extra 500BTUs comes from? Is it more efficient or am I just paying to have more heated water passing through them?

The higher rated radiator has a larger surface area or extra 'fins' on the back so that the heat from the water can be transferred to the air more rapidly, it is more efficient transferring the heat from the water to air. But you can't get something for nothing so the higher BTU radiator will have lower temperature water in the return pipe to the boiler, so the boiler will work harder to heat the water (either by increasing the gas to the burner or by switching on more often) - costing more.

robv_3

TimBuckTeeth wrote: »

The higher rated radiator has a larger surface area or extra 'fins' on the back so that the heat from the water can be transferred to the air more rapidly, it is more efficient transferring the heat from the water to air. But you can't get something for nothing so the higher BTU radiator will have lower temperature water in the return pipe to the boiler, so the boiler will work harder to heat the water (either by increasing the gas to the burner or by switching on more often) - costing more.

Replacing your radiators with higher output can reduce your heating bills when used with a lower flow temperature.

There are a number of ways to measure heat output (delta T). Make sure you are comparing like for like, everyone should be using Delta T 50.

cgray25

Thanks Tim and Rob, good info there - not sure what Delta T50 is (a scale for difference in temperature I pressume?) but I'll give it a read on google.

inmypocketnottheirs

Try a Mears calculator to work out the heat loss for each room.