Air Source Heat Pumps Vs. Storage Heaters (Eco7)

[Deleted User]

ProDave said:

ASHP should be CHEAPER than E7.

Storage heaters use resistance heating, so 1kW of electricity consumed puts 1kW of heat into your house.  All that storage heating brings to the party is a cheaper night time rate to charge the heaters but at the expense of a higher day rate for everything else.  The difference between day and night rate is not as much as it used to be so the benefit is arguably less than it used to be.

ASHP's on the other hand extract heat from the air.  So typically every 1kW of electricity it consumes it puts about 3kW of heat into the house.  That is not some form of magic trick, that extra energy has come from cooling down the air flow through the ASHP.

So the night E7 rate would have to be 1/3 of the day rate for storage heaters to make sense now compared to an ASHP.

BUT and there is always a but, there is a LOT of work to install an ASHP into a house that has nothing at the moment, ideally under floor heating but if not radiators will work.  That is a LOT more work that installing some storage heaters.  IF someone is going to stump up the money to properly install an ASHP by way of a grant, bite their hand off for it.

Not magic, as you say. It's called a "heat pump" because it doesn't generate heat, it moves it. So it can be more than 100% efficient because the energy needed to move heat is less than the energy needed to produce it.

It is moving heat from outside your house to the inside, basically the reverse of an air conditioner.

peterhjohnson

ProDave said:

ASHP should be CHEAPER than E7.
...
 So typically every 1kW of electricity it consumes it puts about 3kW of heat into the house.  

Let's take (for example) the Economy 7  rate from Octopus which is about 21p/kWh and with a heat pump it's 21/3 = 7p/kWh for the heat you actually get. Sounds good but their gas rate is also around 7p/kWh. OK, some of the energy supplied by gas will be wasted up the flue but I'd suggest that the best option may be gas when you factor in capital cost, hot water heating, etc.

Of course, if you're getting your electric from solar, that may be better still. And gas prices are rising faster than electric. But, today, I'd go for gas

ProDave

peterhjohnson said:

ProDave said:

ASHP should be CHEAPER than E7.
...
 So typically every 1kW of electricity it consumes it puts about 3kW of heat into the house.  

Let's take (for example) the Economy 7  rate from Octopus which is about 21p/kWh and with a heat pump it's 21/3 = 7p/kWh for the heat you actually get. Sounds good but their gas rate is also around 7p/kWh. OK, some of the energy supplied by gas will be wasted up the flue but I'd suggest that the best option may be gas when you factor in capital cost, hot water heating, etc.

Of course, if you're getting your electric from solar, that may be better still. And gas prices are rising faster than electric. But, today, I'd go for gas

It is probably fair to say, a heat pump is very attractive to people like me who do not and never will have a mains gas connection.  so I don't have that option.  So a heat pump lets me get close to cost of gas that I can't have.

Plus No gas standing charge to pay.

This thread is about discussing the different options available to an all electric house that presumably cannot get gas.

[Deleted User]

Gas is much worse for global warming. You are just outsourcing the cost to other people, many of whom have not even been born yet.

Bendy_House

peterhjohnson said:

ProDave said:

ASHP should be CHEAPER than E7.
...
 So typically every 1kW of electricity it consumes it puts about 3kW of heat into the house.  

Let's take (for example) the Economy 7  rate from Octopus which is about 21p/kWh and with a heat pump it's 21/3 = 7p/kWh for the heat you actually get.

Are these figures correct?

If the E7 rate is ~21p/kWh, that'll be the overnight cheap rate which charges up the SHs? But the ASHP will be largely drawing power at the full rate, surely, which must be approaching 50pkWh? So the ASHP will be costing at third of that, so ~17p to run? Still better, but not as convincingly.

As pointed out before, ASHPs run at much cooler temps, so expect the rads to be 'very warm', but not 'hot'. I guess around 40+oC instead of 65oC, ish?

I would hope that this would still be ok, because it sounds as tho' they are having the most effective type of wall insulation added, and that's to the internal wall surfaces - good move.

Jake, are they doing anything to the floors in order to ensure they're draught-proofed and, ideally, also insulated too?

And, how much more will they need to pay for the ASHP over the storage heaters?

In short, if the ASHP system 'works', then I would suggest it'll make the house hugely more saleable. If it 'works' but can't quite cope with the coldest temps - of which we tend only to have a few weeks each year - then they may need to supplement the living area with a plug-in heater, like and oil-filled portable type. Yes it'll add running costs, but you do need to not freeze.

If it generally works - and it would only do so with good insulation (which they appear to be having) - then it is surely a very big 'plus' for the house.

It also leaves options for the new owner to perhaps fit PVs feeding batteries to power the ASHP - now that should be a cheap system to run!

Alderbank

Very interesting and thoughtful posts from peterhjohnson and Bendy_House. Thank you!

I live on the east coast of Scotland. It is not particularly cold (for Scotland) and people here are canny with their money.

Estate agents I know locally say that the few houses with heat pumps are very difficult to sell. Buyers see them as noisy ugly money pits needing lots of maintenance and fear being left with an outdated white elephant in a few years time. They say there is no return on investment at all - buyers would prefer to have a 'proper' (they mean mains gas) heating system. 
By contrast, and quite illogically to my mind, buyers love log burners! In spite of all the work and mess, houses with a log burner fly off the shelves.

Perhaps the trick here is if you have a GSHP or ASHP and you need to sell, fit a log burner in the living room?