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Author Topic: Cost effectiveness of heat pumps  (Read 3939 times)
Ian
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« on: July 19, 2006, 11:14:08 PM »

This could be contentious....

Have been trying to evaluate the relative costs of energy over the last few weeks and I have been suprised that I was so out of touch.

I (previously) thought that utility gas was the cheapest, followed by maybe bulk liquid gas, then maybe utilty electricity and top it off with bulk oil. It felt "right" as oil is now US $75 a barrel now - right ?

Quoting prices I am trying to remember rather than looking at the SEDBUK site right now (so it could be wrong but I think the relative order is right)...

Prices per kW hour in pence
Oil = 1.71
Gas = 4
Solid fuel = I cannot remember

I assume Calor to be around 6p

My own electricty is 10p

So oil is the chepest (even allowing for boiler inefficencies) !

Even if you get a 1+3 COP from a heat pump, it will still be less cost effective than burning oil.

The only time I can see that a heat pump will be more cost effective than oil is to operate the heat pump ONLY during an Economy 7 period. In my case I think my Economy7 costs are around 4p a unit so a 1+3 COP would be better than burning oil.

Energy prices are a roller coaster and are probably going to stay that way in the medium term future so it is a lottery as to which fuel you opt for - but it is not so clear cut as I was expecting.

Comments anyone ?

Regards,
Ian
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NickW
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« Reply #1 on: July 20, 2006, 06:26:50 PM »

Those figures look dodgy. I pay 2.2-2.3p per kwh for gas. I recently worked out for a friend that her 28 second oil (kerosene) was costing just under 3p a kwh. On that basis gas is the cheapest option, next is oil and heat pumps which are comparable ( unless you can utilise off peak - in which case the HP is cheaper) Calor and solid fuel is invariably more expensive
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Ian
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« Reply #2 on: July 21, 2006, 08:06:14 AM »

Oops - NickW, you are correct - the figures were dodgy ! (Too much beer and BBQ and late night posting again.. )

I have just taken these figures from the Sedbuk site :

Costs per kW hour in pence

Gas = 1.41
LPG = 3.11
Oil = 1.71

So the cheapest is, indeed utility gas. However, other than running a heat pump on locally generated power or a "low cost" utilty electricity supply such as Economy7, heat pumps are at the bottom of the list.

Any other comments anyone ?

Regards,
Ian
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martin
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« Reply #3 on: July 21, 2006, 08:51:47 AM »

I think another important consideration in choosing a power source is to decide who's going to be holding you to ransom - with gas, that'll be Vladimir Putin (not my favourite choice) - oil will be George Dubbya and his lap dog.........extrapolating that argument brings you firmly back to renewables! As Ian says, it's a volatile, ever-changing market! Roll Eyes
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NickW
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« Reply #4 on: July 23, 2006, 06:19:07 PM »

Looks like Sedbuk need to update their figures - they look really old. If you do find someone willing to sell gas at 1.41 pence a kwh in the UK market Im interested in buying about 1bn cubic metres  Wink
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Ivan
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« Reply #5 on: July 23, 2006, 11:45:34 PM »

heatpumps have never been considered to be the best option in terms of raw fuel costs. However, they do have an advantage 1. where mains gas is not available, 2. if they utilise at least a proportion of off-peak electricity 3. avoids the hassle of oil tanks, running out of oil, leakages and resultant environmental fines etc.

Heatpumps are massively more popular in Southern Ireland, where electricity prices are reasonable, very few houses are connected to mains gas, and the cost of transporting fuel such as oil by road is high.

Ivan
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NickW
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« Reply #6 on: July 24, 2006, 08:10:03 PM »

To add to Ivans comment heat pumps are a much more environmentally friendly use of electric for heating than using electricity directly.
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mtimm
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« Reply #7 on: July 26, 2006, 09:13:21 AM »


Heat pumps are massively more popular in Southern Ireland

Ivan

This is true even despite the high prices.
But some of the popularity is due to impulse buying of a relatively new idea based on quoted figures, some claiming C.O.P of over 5.

I have heard a lot of complaints of the cost of running Heat pumps.


Dont get me wrong I am not Knocking heat pumps I have one fitted myself, but in alot of cases the expectation (and some times claims) of what a heat pump can do are well off the mark
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Ivan
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« Reply #8 on: July 27, 2006, 02:22:59 AM »

All heatpumps should have a standar COP rating - based on a set temperature difference. If you reduce the temperature difference for example if you were taking heat from a source at 25C and trying to heat to 30C, the COP would be much greater. I have seen experimental data showing some heatpumps with COP as high as 6.5 - but for very low temperature differences. These heatpumps quickly revert to COP of 4.5 or so, under standard conditions. I guess some suppliers/salesmen are using this to their advantage, and making claims that would not reflect real-life performance.

Ivan
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