Ditching gas, going electric immersion only, a wee project

isvana

@Solarchaser - many thanks for writing up your experiences.

I had been wondering about a heat store system as part of my 2022 modernization / extension but ended up with a conventional gas CH system as I could not find any reasonable research on stored heat systems. FWIW my architect was a bit dismissive of air sourced heat pumps (as of 2021) and we dont have enough garden for ground (horizontal or vertical) heat pumps. I did have space for underfloor tanks like you but my research only found commercial systems and the local plumbing teams were not very encouraging! So invested instead in PV and insulation...

I think you are definitely leading the way here. Full kudos to you. 

Reed_Richards

I wondered for a bit about whether PIR insulation has the compressive strength to bear the weight of a tank of water.  The figures I found suggest that it does, or at least the right type does.  I presume you have checked/will check. 

I also found a Kingspan product that uses evacuated insulation: https://www.kingspan.com/gb/en/products/insulation-boards/floor-insulation-boards/optim-r-flooring-system/ 

Reed_Richards

isvana said:

... ended up with a conventional gas CH system ...

I hope it was a modern low-temperature gas CH system rather than a conventional one.

Solarchaser

That's very kind of you Isvana.

I think the ideal scenario for heatpumps would be wet underfloor heating fed from a heatstore of some description as it's a lower temperature way of heating, (and would see less standing heatloss) but thats not what I have.
Due to being all "normal" radiators I really need the higher temperature that direct immersion brings, and in that shorter time frame of off peak electricity. 
I am likely to replace the livingroom radiator from double panel to triple as suggested by Reed a few pages ago, I just haven't fully decided.
I'm also likely to extend my underfloor pex loops to cover more of the back of the livingroom as its worked better than i thought, and the family would like it under the dining table also.

Reed, I've looked into vacuum a bit since my last post, but unfortunately as we both suspected, it's prohibitively expensive at around double the price of pir for a panel 1/4 of the size.
On the compressibility of pir, honestly no, I haven't done calculations as such.
I've worked a bit with pir and with point loads It does compress a certain amount, and certainly with 180kg spread over approx 800x100mm (the brackets that hold the tanks footprint) I expect there to be some sinking.

I've been toying with the ideal of putting a sheet of osb on top of the first layer of pir for load spreading, however I may just accept the fact of some sinking because the height I have the tanks at just now is OK, and if I add 100 mm of pir, then really I need to excavate another 100mm of brick infused soil/clay throughout the whole area, and remembering that all of this will be done in a crawl space, so essentially on my knees or hunkers, it's going to be painful enough.
Everything is a compromise.

If only I had an actual standing space under the house, or a basement,  this would have been done with vertical tanks instead of horizontal,  and that would have saved a whole load of hassle, and destratification. 

Reed_Richards

Solarchaser said:

Reed, I've looked into vacuum a bit since my last post, but unfortunately as we both suspected, it's prohibitively expensive at around double the price of pir for a panel 1/4 of the size.

By size do you mean area for the same thickness?  Its about 3 times the thermal resistance of PIR for the same thickness (I think).  So a sheet 50mm thick would have the same thermal resistance as about 150 mm of PIR.  So the difference would be 4 x 2/3 = 2.67 times the price for the same amount of insulation per unit area.  That's not good; I suppose you would use it when you really want the insulation but haven't got enough space for thick PIR.

Solarchaser

Only ones I can see as an actual offer is on ebay
https://www.ebay.co.uk/itm/134412285997?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=Auuzo-fhQU-&sssrc=2349624&ssuid=DtbsXk1pRsq&var=&widget_ver=artemis&media=COPY

That's £500 for 7 panels that are 600x1200 x 40mm
So equivalent to 120mm by your reckoning.
Normal pir board is 1200x2400 so 4 times the size

60mm celotex is £33.60, so 2 of them would be 67.20 for same thermal resistance. 
So roughly 4 times the cost for vacuum, (calling it 8 panels instead of 7 brings £250 for ease of comparison) and thats as an ebay offer.

I'm most likely to pick 50mm celotex at £26 because I'll be using that to insulate my loft in double layers and so for say £200 will be able to do all tanks double 50mm.

Solarchaser

Solarchaser said:

Solarchaser said:

Received my octopus bill for mid November to mid December and so compared it to last year's bill.
2021 bill was 715kwh
641 off peak and 74 peak at a total of £47
Gas for the same period was 1500kwh @3.6p so £64
So £111 combined

This year its 1940kwh
1700kwh off peak and 240 peak
No gas, so total is £118, so looks like a increase of £7 over last year

However if I was still on gas, the gas bill would have moved from 3.6p to 10.3 so the £64 would now be £154 which would have taken me to £201, and in that respect I've saved £83

A bit of positivity

Got my bill in for mid December to mid January. 

Jan 21's bill was
Gas1765kwh £51
Electric 783kwh £58
Total 2548kwh = £109

Jan 22's bill was, (well I don't know exactly as the bill is December to Feb for both gas and electric, so I'll just half both of them)
Gas 1615kwh gas
Electric 569kwh off peak 60kwh peak
Total 2248
Elec £42 and gas £69 = £111
Gas now would be £166 so total would be £208

Jan 23's bill is
1818kwh off peak 382kwh peak
Total 2200kwh = £143

So as with last month, looks like an increase of £33 in comparison with the previous year, but when compared with using gas at its current price its a saving of £65

That's basically if I changed nothing else, my tarrif runs out in a months time, whereby my electricity prices will increase more than double,  in the last two years the gas went from 2.53p/kwh to now would be 10.3p/kwh, so a 4 fold increase.
It was the increase in gas price to more than the off peak electric price which convinced me to push the button in april/may last year.

Bill has arrive for mid January to med February. 
This will be the last bill with the 4.5p off peak rate sadly.

Tesla was hit a couple of weeks ago, and while it's being repaired,  intelligent octopus is not available to me, so instead of 6 hours at 10p, I'll have to make do with 4 hours at 12p on octopus go.

Anyway to the bill
Feb 22 was:-
1615kwh of gas
569kwh off peak and 60kwh peak electric
So a total usage of 2244kwh
At a cost of £111

Now the gas alone would be £161

Feb 23 was:-
2020kwh off peak
237kwh peak
So a total usage of 2257kwh
At a cost of £132

So again on the face of it a £21 increase and a 13kwh increase too.

However for the last couple of years car charging has been free on public chargers, and now it's not, and so this month and last I've been charging both EVs at home, and according to the Zappi that represents 142 kwh onto mid January's bill and 280kwh onto mid Februarys bill, so for an honest comparison I should remove 142 @4.5p last month (£6.40) and 280 @4.5p (£12.6)this month.
This takes the increase down to £8.40 and take the kwh usage to 1977kwh and so a reduction of 267kwh.

I expect the next couple of months to really show the difference as solar comes back in, there will be less requirement for the heavy off peak usage, and more of the sun heating the tanks, whereas previous years gas usage shows only a slight decline between February and May.

Looking forward to see the results.

Reed_Richards

Solarchaser said:

Tesla was hit a couple of weeks ago, and while it's being repaired,  intelligent octopus is not available to me, 

I presume "Tesla" means the car and not the home battery?  But how does that work?  Is Intelligent Octopus so intelligent that it knows what it's charging and that your car is not there?    

Solarchaser

Tesla being the car yeah.
My home batteries are definitely not tesla... though tesla batteries are more pretty 

Intelligent connects to certain car makes and talks to them about charging.
To sign up you need to charge the car while on the octopus app and it confirms some sort of connection with the car.
But it's only for certain makes, nissan are not on it, so I can't join with the leaf, loan car is a polestar and it's also not on there.
Heres the lost of supported makes:-

Reed_Richards

So you can use the cheap electricity for whatever you like but only whilst the car is connected to the charger?