Calculating BTUs - underfloor heating and towel rail

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We are redoing our bathroom and want electric underfloor heating and a towel rail. I have found some on line calculators which tell me the total number of BTUs I need to heat the room (although different ones give different results... )

BUT how do I work out how many BTUs the elec underfloor heating is going to give me, so I can choose a towel rail to make up the difference? I can't seem to find a site which tells me how many BTUs per sq ft of underfloor heating or anything like that...

Any tips appreciated

I was hoping someone more knowledgeable can answer this, but I would say that your underfloor heating supplier should be able to provide you with this information and then you see if it is enough to warm the whole room up (corroborated with the information on the total number of BTU units gleaned from the online calculators, which you hopefully already know by now).

We also have electric UFH in all our bathrooms and to be honest we don't really need other source of heat (I.e. Extra radiators, towel rails), but we did put in towel rails too so that we can get nice warm towels after bath/shower. Make sure you go with dual fuel ones so that in the summer when your central heating is off, your towel rails can still stay warm.

belated thanks audrey! Yes I guess I'll ask the underfloor heating people. That's good that you don't really need extra heating... sounds like we may be ok with a small towel rail (which is all we have space for)

I very much prefer to calculate in kW.

Your uf heating, radiator and towel rail are pretty sure to have kW ratings, and so should your heat loss calculator

Remember that you will be insulating your towel rail in thick towels to prevent heat getting out.

Energy from electricity costs about three times as much as energy from gas.

I just looked at a typical underfloor heating mat and it was 150W per sq metre.

A bathroom might need between 500W and 1kW of heat.

There are about 3,400BTU in 1kWh

3kW is the output of a powerful fan heater.

1kW is about the output of a single radiator 1 metre long.

Thanks PigletJohn! Hmm sounds like we might need a bigger towel rail or a mini rad as well as the towel rail (there won't be much u/floor heating as not much floor, and the room has 2 external walls and 2 velux windows).

You can get a combined radiator/towel rail contraption.

Or some people put an ordinary rail above or close to a radiator. As long as you have a TRV on it, an oversized rad will not overheat the room (but will warm it quickly).

If you have a nearby hot water cylinder the rad or rail can be plumbed to warm up at the same time as that, even when the CH is off.

Thanks PigletJohn. I think a small rad next to the towel rail (tucked under the basin) may be the way forward.

hot water cylinder (megaflo) is in the cellar so miles away... does that mean I can't have the towel rail plumbed to go on with the hot water?

You might manage it if the boiler was nearby. Otherwise probably too tiresome to run the pipes.

nope boiler's down in the cellar too. ah well. thanks v much for your help