Underfloor electric vs GCH

alexandicity

Hello!

I am renovating a flat that doesn't have a gas connection (and so uses ugly electric brick radiators throughout). There's gas in the building, but no meter or piping to my flat. I always assumed that I would shell out £5k+ to get the connection to the flat, install a boiler and associated piping, and some radiators.

The justification for this was the lower running costs and the boost to resale value that comes with GCH.

However, that's an expensive option. Since I'm ripping up the floors, there's an opportunity to put an electric (dry) underfloor heating in all the rooms. I quite like this idea, as electric is simpler, quieter and more reliable. I'm also an electrical engineer so I have something of a bias towards it I'm happy to use usage water heaters in the shower and kitchen.

But, electricity is expensive. I wanted to know if any of you have any knowledge on the relative running costs of GCH and underfloor-for-heating might be? I understand that underfloor is more efficient, which might offset part of the electrical cost...

The other question is whether a electric underfloor setup would give the flat value a boost in a similar way to GCH?

Thanks!

macman

Electric heating on standard rate is approx 300% more per kWh than gas CH.
The 100% efficiency compared to a gas boiler does not wipe out that difference.
As you rightly say, gas CH will greatly improve the value and marketability of the property, so why not find out the actual costs of a gas install?

zolablue25

Why not go for a gas fired underfloor system if the floors are coming up anyway?

Richie-from-the-Boro

alexandicity wrote: »

Hello!

I am renovating a flat that doesn't have a gas connection (and so uses ugly electric brick radiators throughout). There's gas in the building, but no meter or piping to my flat. I always assumed that I would shell out £5k+ to get the connection to the flat, install a boiler and associated piping, and some radiators.

The justification for this was the lower running costs and the boost to resale value that comes with GCH.

However, that's an expensive option. Since I'm ripping up the floors, there's an opportunity to put an electric (dry) underfloor heating in all the rooms. I quite like this idea, as electric is simpler, quieter and more reliable. I'm also an electrical engineer so I have something of a bias towards it I'm happy to use usage water heaters in the shower and kitchen.

But, electricity is expensive. I wanted to know if any of you have any knowledge on the relative running costs of GCH and underfloor-for-heating might be? I understand that underfloor is more efficient, which might offset part of the electrical cost...

The other question is whether a electric underfloor setup would give the flat value a boost in a similar way to GCH?

Thanks!

Historically the cost of leccy over the decade has risen less by %£ than gas, unsurprisingly they are closer to 50-50 retail price than they ever were, the pedicted cost rise this year is 14.1% for leccy and gas will be 19.8% [source: BBC news website]. You know I've always assumed while people are going to have a thousand questions there are in fact two .. .. only two questions where a dwelling is already 'opened up' and laying the floors is a given easy cost relatively free option. The the real questions assuming your home is already Part L compliant would be :

- maximum underloor insulation [running costs and warm up times] quality and values
- zone [room] control and what figure of output per Sq Mtr [ should be 200W per square meter [ish] covering 90% of the available floor area

Underfloor is always going to be a 99% efficient converter of energy and carries a 'lifetime' warranty. Even if gas was available [assuming Putin never switches it off] and cheaper it carries heavy replacement / maintenance costs which over a lifetime would outweigh any price differential.

Your question on costs there are hundreds of sites with 2012 figures that taken with a pinch of salt [its really decided by insulation] come out roughly 6/12 to :

A 3m² Bathroom system heating for 3 hours a day would cost around £13.60 per year
A 3m² Bathroom system warming only the floor for 3 hours a day would cost roughly £7.80 per year
A 5m² Kitchen system heating for 2.5 hours a day would cost around £18.90 per year.
Heating a 10m² Conservatory system for 8 hours a week would cost in the region of £22.70 per year

alexandicity

Macman - yes, that is the calc I do and that basic truth is by biggest dissuasion. I am just trying to make sure I haven't missed anything For purposes of calculation, do you know what a GCH's system efficiency is (as opposed to boiler efficiency)?

Zolablue - a good idea, but separate from this problem. If I decide to go ahead with the GCH install, I might well also opt to go for wet underfloor. Watch this space!

Rachie - this is the kind of complication I was thinking of. Electricity prices are unlikely to be less than gas in the next 10 years, but the gap between them seems sure to close. Interesting point about the insulation; is this done in the same way as in lofts etc? As in, the thickness of the under-floor spaces being a determining factor?

Cardew

alexandicity wrote: »

Macman - yes, that is the calc I do and that basic truth is by biggest dissuasion. I am just trying to make sure I haven't missed anything For purposes of calculation, do you know what a GCH's system efficiency is (as opposed to boiler efficiency)?

Modern gas boilers have a theoretical efficiency of over 90%, however that is assuming it will always be in condensing mode. The jury is out on 'real world' efficiency - but I suspect around 85% would be a reasonable estimate.

Although you mention electrical water heaters for shower and kitchen, you need to factor in the savings from water heating.

The other big factor that favours gas CH is the ability to heat the flat quickly. Electrical UFH is low temperature and takes time to warm the room. Not so a gas boiler that can supply water to radiators at 80C so a timer set say 20 minutes before getting up or returning to the property, will result in a warm flat.

Are you sure about £5k for gas supply when gas is already in the building? Some people pay a fraction of that for supply to a house from gas main in street - which involves digging a trench.

alexandicity

Hi Cardew,

Thanks for your thoughts. Hadn't considered the warm-up time much, but it does seem an important factor in overall running costs.

The £5k isn't so much for connection to the gas, but for installation for gas in the flat. That includes a boiler, flue, piping, radiators, certification and the actual meter installation. All that will probably come to quite a bit more than £5k, although it's hard to get a solid estimate. I'll have to talk to a gas guy about that..!

Richie-from-the-Boro

Best warm up time & lowest loss.

- warm up time depends on what is below the underfloor heating system to stop downward heat transmission and how many watts per meter you install
- using U values is / are / what the industry uses, and has been around for years. The calc applies to gas leccy wood burner whatever but its complicated
- there will be U value calculators all over the interwibble somewhere covering ground bearing / suspended / and non / concrete and suspended timber etc
- in short more of the better insulation type below the heating and the best conductivity material above will give the lowest resistance convection