ASHP and SunAmp cheaper than Oil tank? Confused

[ProDave]

Quote

 

Space heating fuel estimation: 6600 kwh per year

Water heating estimation: 2300 kwh per year
 

 

 

If you go for the simplest solution (like I have)  ASHP driving UFH directly, and heating an UVC to 48 degrees for DHW:

 

Assume a COP of 3 when heating the UFH so that's 2200KWh of electricity @15p per KWH that's £330 per year for space heating.

 

Assume COP of 2 when heating DHW so that's 1150KWh of electricity @15p per KWh that's £172.50 per year for hot water.

 

The real figures will be cheaper than that, as most of the time the COP figures should be better than that, and you will probably find a cheaper electricity tariff than we can get up here (extra 2p distribution surcharge)

 

The fact you can halve (or better) the DHW costs by using a simple unvented cylinder is what swung me away from the Sun Amp solution.  Yes the UVC will have a higher standing heat loss than the sun amp, but that heat loss is more than made up by the saving in heating cost.  Plus for half the year that "loss" is just helping to heat the house.

 

The sun amp solution makes sense if you have a lot of solar PV so are always looking to use up surplus PV generation, are short of space, or the particulars of the install mean the standing loss from a conventional tank becomes an overheating nuisance. 

[Roz]

20 minutes ago, ProDave said:

 

Assume COP of 2 when heating DHW

 

The fact you can halve (or better) the DHW costs by using a simple unvented cylinder is what swung me away from the Sun Amp solution.  Ye

 

Can you explain this to me for using a UVC (unvented cylinder?) ? It's not something I have come across yet. Does that include having an electric boiler?

[joe90]

30 minutes ago, ProDave said:

Yes the UVC will have a higher standing heat loss than the sun amp, 

 

We have been told this but my insulated DHW tank does not heat the airing cupboard like my wife would like! (Water at 47’ ish) I am doing the same as @ProDave and will monitor bills but I have confirmed with my supplier (green energy) that they do E7 and E10 and plan to go to one of them when the house settles down (and I get time!!!).

Edited December 11, 2018 by joe90

[newhome]

40 minutes ago, Roz said:

 

Can you explain this to me for using a UVC (unvented cylinder?) ? It's not something I have come across yet. Does that include having an electric boiler?

 

In my simple words (as I don’t understand all of the technical stuff). The UVC is a tank that stores hot water produced by the ASHP. The ASHP also supplies the UFH separately. No electric boiler (probably a back up immersion) as the ASHP acts as the ‘boiler’. 

[ProDave]

46 minutes ago, Roz said:

 

Can you explain this to me for using a UVC (unvented cylinder?) ? It's not something I have come across yet. Does that include having an electric boiler?

An UVC is a hot water tank, but unlike old fashioned ones that were fed from a header tank in the loft, they have a mains water feed in to the bottom (via a pressure reducing valve supplied with the tank)  and also have an over pressure and over temperature release valve so they won't explode if something goes badly wrong.

 

It can be heated either directly by an immersion heater, or by a heat input coil that can be fed from either a boiler or a heat pump.

 

The advantage being you can heat them to any temperature you want with the heat pump, unlike a sun amp that needs the input water temperature to be at least 65 degrees.

 

No electric boiler needed.

[Roz]

7 minutes ago, newhome said:

 

In my simple words (as I don’t understand all of the technical stuff). The UVC is a tank that stores hot water produced by the ASHP. The ASHP also supplies the UFH separately. No electric boiler (probably a back up immersion) as the ASHP acts as the ‘boiler’. 

 

1 minute ago, ProDave said:

An UVC is a hot water tank, but unlike old fashioned ones that were fed from a header tank in the loft, they have a mains water feed in to the bottom (via a pressure reducing valve supplied with the tank)  and also have an over pressure and over temperature release valve so they won't explode if something goes badly wrong.

 

It can be heated either directly by an immersion heater, or by a heat input coil that can be fed from either a boiler or a heat pump.

 

The advantage being you can heat them to any temperature you want with the heat pump, unlike a sun amp that needs the input water temperature to be at least 65 degrees.

 

No electric boiler needed.

 

Thanks both. So you get the COP of 2 by feeding it from the ASHP? How much do the UVCs cost?

So the main problem for me is space. Currently the only place it could go is where we were planning to put the washing machine, in an upstairs landing cupboard. And then I don't know where the washing machine would go. Unless we can site the tank higher up the wall, and have the washing machine underneath?

[ProDave]

I fitted a 300 litre UVC. You need a larger one as you are storing the water a bit less hot, and you need one with the high capacity heat input coil.  Mine was in the region of £850

 

They are quite tall, about 1.8 metres, so I doubt you will get a tank and a washing machine in that cupboard, which may be a good argument to swing it in favour of a sun amp for your application.  But both the washer, and the sun amp are heavy, so whichever goes on top will need a substantial shelf to sit on.

[epsilonGreedy]

On 10/12/2018 at 22:57, PeterW said:

 

Last in ground tanks we had were £2200 each, and that was for 2000 litre units.... and that was 4 years ago. 

 

Best supplier by far in that area is LPG Direct and they do underground tanks but I think they are rental only at about £20 a month. 

 

I was using LPG Direct info obtained when you first mentioned them to me 6 months ago.

 

In a call today it was confirmed underground tank installation is £250 in a pre prepared hole. Annual tank rental is £70. £0.375 per liter fixed for 6 months of the 2 year contract.

 

Defo the cheapest off mains gas new build setup cost but I have no idea how many years it takes before hi tech options pay back their setup cost premium.

[PeterW]

That’s good then ..! Didn’t know they were doing tanks cheap still - did they give you an uplift charge at the end of the contract too..??

[epsilonGreedy]

1 hour ago, PeterW said:

That’s good then ..! Didn’t know they were doing tanks cheap still - did they give you an uplift charge at the end of the contract too..??

 

 

I asked a question about end-of-contract tank ownership complications and was told there is an industry agreed tank valuation formula which is applied when a new LPG supplier is selected by a householder at the end of the statutory 2 year supply period. Is this what you mean by an "uplift charge"?

 

If you suspect the current favourable tank supply terms are a transient loss leader maybe I should act quickly because bulk tank LPG is about 35% cheaper than bottled gas and would represent a saving of a few hundred £ heating the static caravan for 18 months. On the other side of the coin I would prefer to delay and see how much further air source heating installation costs fall.

[Ed Davies]

1 hour ago, epsilonGreedy said:

Is this what you mean by an "uplift charge"?

 

But how much will the charge to take the tank away if somebody decides that, e.g., an ASHP would be better than LPG? Perhaps it's free (though I suspect not) but it would be good to know for sure.