I think my numbers were a bit out. I've checked the tank again, and it is a Supercal double lagged 210 litre, 1500 x 450, and has declared losses of 3.16 kWh/ 24 h, which would be a rather lower continuous loss of 132 Watts.
When I had this larger tank fitted, it had it put in the garage, along with the Monsoon pump, and a tiny radiator installed in the airing cupboard.
Chris
so anyone know any solution for gas system?
Heat pumps can work on a properly designed heating system. Unfortunately too many cowboy outfits are advertising as though a heat pump is a straight replacement for a gas boiler and indicate that there may be large "Government" grants to offset some or all of the cost. What they tend to fail to mention is the costs associated with bringing insulation up to standard and the modifications needed increase the size of radiators etc.
the etc includes the hot water storage tank which needs to be much bigger since the heating coils are so much bigger. No room in our house, so we had a new gas booiler. The old one was 35 years old. I think we are using less gas, but the winer will give the real answer.
My tank got bigger because it includes a 50 litre buffer, which isn't actually necessary but the vendor's instructions are dumb so the installer included one, and some thicker insulation. It wasn't bigger due to the size of coil - they just wrap up the longer coil into a tighter spiral.
It got a few inches wider (due to the insulation) and maybe a foot taller (the buffer). It fit in the same spot as the 1970s tank it was replacing.
Theo
To be fair to the cowboys, a straight swap is the holy grail that we all seek. I’ve tried to get quotes for a heat pump and the only company that would give me one was going to cost over £23,000 for a 5 bedroom house.
Now that kind of money pays for a f*ckload of gas (and several replacement boilers). Yes, grant money will help but I get the feeling that prices are being jacked up by the value of the grants and that we’re being fleeced.
If heat pump efficiency was high enough to make a “sub-optimal” cheaper to run than gas then I would be prepared to suck up (some of) the installation cost but the uncertainties surrounding system efficiency and the potential disruption of replumbing are putting me off the whole idea.
In an ideal world I’d like a heat pump that could be a straight swap for my existing gas boiler that would cost no more to run than my gas one with no (or at least minimal) system modifications.
Tim
Wouldn't we all? If that were the case, they would sell like hot cakes.
They may (at the moment) be much more efficient than gas boilers, but their heat output is so much lower that they need to be run more of the time to do the same job, or need to be much bigger and noisier. And even then, they are not great when it's really cold outside.
Of course, it may just be market segmentation: when all the people with silly money to burn have burned it, maybe they'll start selling to less well-off people at a rather lower cost.
Did you ask Octopus? It sounds like a lot of installers are rushed off their feet and only interested if you cross their palm with silver. Octopus seem to have more capacity for doing installs in volume and bringing the prices down. I've heard install costs comparable with a gas boiler after the grant.
Yes, there is always the risk of that. Did you get a heat loss survey and what did it say? What size of pump did they recommend, any other works?
Is the house 'complicated'? (ie is it rambling farmhouse rather than a
1960s+ box?)High temperature heat pumps (where there are two compression cycles, effectively two HPs in series) are more of a swap with a boiler, but you lose some efficiency. It depends on your numbers whether that makes sense.
Theo
But around 4x the cost for the low temperature ashp and with higher running costs than with price of gas (COP adjusted).
Also, if a replacement gas boiler is to be fitted in the same place as the old gas boiler the labour charges will be a lot less.
The "green"energy organisations now suggesting higher temperature heat pumps are not that interested in saving you money but in saving an estimated 50% in CO2 emissions.
Octopus have the Cosy 6, which produces up to 75C water with a SCOP of 3.4 (at 50C). I don't know what they cost since Octopus are supply-and-fit, but I've heard their quotes are competitive. That's what I mean about looking at the numbers - it's possible they can be made to work, but we don't have enough data.
...which is something we need to do.
I also wouldn't bank on the gas:electricity price ratio staying the same as it currently is.
Theo
The problem is that 'renewable' electricity is three to five times the price of the gas.,
And when you most need heat - at subzero temperatures - the heat pumps fail to offer any significant power output and need to be supplemented with actual real electrical heating elements
Now a good ground sourced installation is way better but you are looking at a capital cost far exceeding the ongoing cost of gas.
The real gains are in the massive insulation required in new builds. There heat pumps may be adequate.
But not as retrofits to existing properties designed for 60°C water temperatures in the CH.
No. Electricity will inevitably rise further under Milibrain's 'Net Zero Nonsense'
Currently oil and gas are similar at around 6p/kWh..electricity is at least 20p
On the contrary, my Heat Pump never has the immersions on, they are disabled at the CU. I get ~54C generated for DHW and Heating with only circulation through the system. As for 'Legionaires' no sign yet in several years operation.
The immersion heaters are within the heat pump itself
It is not possible to pump from say 5°C to 54°C with a single heat pump stage
Not on my system - it's a regular cylinder with an immersion.
The HP can control the immersion, but as originally installed there was a separate relay timer box to run it for legionella control.
My system is max 55C. Single stage.
Theo
Not from -5C outside temperature it isn't
That's what it says on the spec sheet. Next time it's freezing outside I'll try it.
(I don't normally run it that high for efficiency reasons)
Theo
Significant factors in climate change are:
The shape of Earth’s orbit, known as eccentricity.
The change of the angle Earth’s axis is tilted with respect to Earth’s orbital plane, known as obliquity.
The change in the direction Earth’s axis of rotation, known as precession.
The rotation of the Earth’s elliptical orbit, known as Apsidal precession.
Milankovitch theorised that these cycles combined to control the glacial cycles, and according to NASA this theory is widely accepted in the scientific community.
The Cosmic Ray flux affects the level of cloud cover, which in turn affects insolation and therefore the climate.
The overall effect of changes in concentration of trace amounts of gasses in the Earth’s atmosphere are negligible when compared to those of the celestial forces mentioned.
The CEO of a Scotland-based energy organisation (I can’t recall which one) said on the radio recently in an interview that “…cheap electricity is for the medium to long term”. Better factor in high electricity prices over the working life of current heat pumps.
I agree you have to know and understand the figures.
The SCOP values are at
SCOP is the seasonal coefficient of performance which is a weighted average of the COP over a heating season. While SCOP may be a good indicator for determining if one ASHP is better than another you may also need the actual COP figures to see how much it will cost to run in a 3 week very cold spell of weather.
It's a 6KW ASHP typically costing around £11K including installation and controls with £7.5k back in grants. The advertised free bit is if the cost = grant.
Octopus are selling it on a reduced tariff scheme of 3 off-peak set periods a day but with a higher daily standing charge, a higher than "capped" rate for peak periods and "capped"rates for all other times. The most economic running costs would be to fully use the off peak periods, which at the current time would be cheaper than gas (assuming favourable weather). The risk with respect to costs is what will happen to the off-peak rate when in a few years time the targets of
600,000/year ASHPs installs are met and there is no longer off-peak times. However, by then we may all have free electricity generated by that free wind and sun :)
Unrelated to heat pumps but relevant to a smart meter as opposed to old-fashioned Economy 7.
We have a plug-in hybrid that we charge overnight at the (old-fashioned) Economy 7 rate. The hours for cheap rate are fixed, as is the price.
As I understand it if we changed to a smart meter we'd get cheap electricity (possibly a little bit cheaper) overnight but only some nights and not necessarily the same hours every night. For charging our car that's useless.
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