"Off-Peak" Electricity Tariff

PoorPauly

Pincher wrote: »

Try out heat pumps? If you can get a COP of 3, then you pay 12p per kWh for electricity, but 4p per kWh in heat. This assumes you have a wet UFH system.

If it works, I think you should change the meters, so you have a single rate meter.

Thanks a lot - sounds interesting. Do you know where I can find more info on that?

Richie-from-the-Boro

PoorPauly wrote: »

Nonsense - the underfloor heating works very well. It most certainly does last into the day and has a huge amount of stored heat - the entire concrete floor block is, in effect, a huge storage heater!!

- the issue is cost, essentially the cost issue exists because you can't swap supplier
- switching from E10 to a single E7 will lose you the afternoon 3 top-up hours
- but will gain (1) a cheaper non-core tariff for all hours, and (2) the ability to swap to a cheaper supplier
- as you will then have an E7 tariff, putting a DUO-NSH in the mix will take care of all other comfort needs

Cheap money well spent !

System

I would say if the ufh lasts time after teatime without the afternoon boost is there no chance you could change the meter for e7 meter then look for a much better tariff else where and maybe use a electric fire for a little top up in the evening. my night rate on scottish power march 2015 is about 5.75 ish and day rate is 12 ish

hebridean

I have an ashp with ufh on the groundfloor and radiators upstairs. I have an e10 supply through a single meter and have found over the past year that the off/peak amounts are pretty much level pegging. After phoning around as e10 does not calculate on the comparison sites found that i could save £150 if i changed and found that i could possibly save another £100 if i came of e10 to a standard rate.
I run the heating from Oct-Apr switched on permenently through zoned thermostatic demand with the water heating coming on three times a day for an hour during the off peak times. During the Summer months the heating is switched off and i'm paying £160 per month which is for a 215 m2 house.

rogerblack

hebridean wrote: »

I have an ashp with ufh on the groundfloor and radiators upstairs. I have an e10 supply through a single meter and have found over the past year that the off/peak amounts are pretty much level pegging.

If you could arrange your ASHP to come on preferentially when the electricity is cheap, then that might moderately reduce your bills.
Only applicable if you're in though!

macman

PoorPauly wrote: »

Nonsense - the underfloor heating works very well. It most certainly does last into the day and has a huge amount of stored heat - the entire concrete floor block is, in effect, a huge storage heater!!

Now I wonder why they don't use concrete as a thermal store in night storage heaters? Compare the R- values.

rogerblack

macman wrote: »

Now I wonder why they don't use concrete as a thermal store in night storage heaters? Compare the R- values.

Concrete absorbs the same amount of heat - but at very high temperatures it can have structural problems.

For night storage UFH - it really depends.
Ballpark.
If you want the temperature to not rise more than 5C overnight, and you're using a 3kW heater to heat it, you need to absorb 24kWh - or so.
This is 5kWh/C.
This would require about 5 tons of water to store this much heat per change in temperature - or 25 tons of concrete - 10m^3.

This is a hugely massive improbably thick slab of concrete - for a 4*5m room, it is 50cm thick.

The other problem is even if you did have a slab this thick on your UFH - the very thickness of the slab somewhat insulates the bottom of the slab from the surface.

It is possible to use massive thermal elements to even out the temperature of a room daily, so you could heat at night for the daytime.

Your normal UFH will not do this.
A couple of hours heat storage - sure.
Staying warm from 8AM to 11PM - well - no.

Richie-from-the-Boro

Assuming a 3" slab, the efficiency of ~U~ starts underneath the slab itself and even before pouring the concrete. The DPM should be laid on top of sand - insulation should be installed under the concrete slab and above the DPM - the DPM should be totally air tight - and extend well above the (1) insulation (2) [thermal mass] slab, (3) the screeded area holding the heating pipes and even the (4) assumed floor tiles and behind the paster board wall.

If the O/P's post assumes the "screeded area holding the heating pipes" is a thermal mass slab - its not | at all | a thermal mass.

hebridean

rogerblack wrote: »

If you could arrange your ASHP to come on preferentially when the electricity is cheap, then that might moderately reduce your bills.
Only applicable if you're in though!

Aye rodgerblack you are right to a degree. I do this in he Spring/Autumn months when the air temperature is just above 10c and it seems to be comfortable enough, but when it drops below that i change it to on demand. I have found that leaving it switched on thermstatically using setback etc works out to be the same cost wise as the pump is not having to work so hard when the ambient air temperature is so low. I set back all areas by 2-3c during the night and at certain times during the day when the house is unoccupied and find that it generally takes about an hour or so to bring the temperature up again.

Pincher

PoorPauly wrote: »

Thanks a lot - sounds interesting. Do you know where I can find more info on that?

Simplistically, just look at how your freezer works.

GSHP : Ground Source Heat Pump

ASHP : Air Source Heat Pump

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