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Author Topic: Is this correct?  (Read 1210 times)
Eccentric Dyslexic
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« on: February 13, 2018, 06:54:33 AM »

Can someone more maths oriented confirm if the info I just found posted on a Facebook group is correct please?

“Its a guide to heating energy costs (prices change but its but not far off)

2.9t wood chip = 10,000 KWh = €370.00
2.6t logs = 10,000 KWh = €430.00
2.1t Pellets (pumped) = 10,000 KWh = €660.00
56g (1KWh) Heat pump = 10,000 KWh = €700.00
2.1t Pellets (bags) = 10,000 KWh = €720.00
1000ltr oil = 10,000 KWh = €850.00
180g(1KWh) Electric = 10,000 KWh = €1550.00
257g (1KWh)  LPG = 10,000 KWh = €1640.00”

Cheers

Steve
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Countrypaul
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« Reply #1 on: February 13, 2018, 07:39:47 AM »

Using the figues in that table, the heat pump only has a performance factor of slightly over 2 (assuming the electric is the same price for the HP and direct) which sounds rather low but without more context difficult to be more specific on. The electric for both appears to be a standard tariff rather then an E7 one that might be used for heating so probably over double what might be charged for an E7 price.

The energy output for oil seems about right at 10KWh/L - the cost is faily volatile, but a quick check on BoilerJuice seems it is around 50p/L so around €600.00.
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M
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« Reply #2 on: February 13, 2018, 07:50:41 AM »

Using the figues in that table, the heat pump only has a performance factor of slightly over 2 (assuming the electric is the same price for the HP and direct) which sounds rather low but without more context difficult to be more specific on. The electric for both appears to be a standard tariff rather then an E7 one that might be used for heating so probably over double what might be charged for an E7 price.

The energy output for oil seems about right at 10KWh/L - the cost is faily volatile, but a quick check on BoilerJuice seems it is around 50p/L so around €600.00.

I seem to recall that a UK ASHP has an average COP of 2.9. Cost wise, as you say E7 would help massively, and provide leccy when the COP is lowest during cold nights, whereas the day rate would hopefully have a higher (on average) COP.

I don't know much about heat pumps, but assume that the COP of GSHP's don't vary day v's night?
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brackwell
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« Reply #3 on: February 13, 2018, 09:06:34 AM »

Natural gas is the cheapest.

As Paul says the HP has to be less than that unless off course you fit it in a system not designed for HP

Wood is always difficult to compare as you can never be sure of the quantity and quality of what you are buying.

If i was buying one of these for my fuel supply then i wood choose pellets which are cheaper than suggested ,made to a standard, easy to store and load,in short a reliable efficient heat source.

However if you can forage your own wood or buy fresh wood and store it long enough to dry then go that way as i do.

Ken
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Eccentric Dyslexic
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« Reply #4 on: February 13, 2018, 09:12:35 AM »

So with a heat pump like this, at 7degrees outside temp with a cop of 4.3 what would the figure be?

https://www.ebay.co.uk/itm/Samsung-Premium-Air-Source-Heat-Pump/391855916556?hash=item5b3c6ec60c:m:mr0_DxvDAZd8tc89q1n4yMQ

A cop of just over two in the example this chap has given doesn’t really show the heat pump in a good light. Maybe he doesn’t sell heat pumps...?

Steve
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Stig
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« Reply #5 on: February 13, 2018, 09:13:41 AM »

One thing not mentioned in that table (apart from the heat pump assumed COP) is the efficiency of the heating appliance.  I know modern gas boilers have claimed efficiencies of over 90% but what's the typical efficiency of a wood burner etc.?
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Westie
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« Reply #6 on: February 13, 2018, 09:17:59 AM »

Well I hope the LPG figure is wrong....

I've used this LPG  convertion ratio...

LPG litres to kWh and vice versa (1L = 6.9kWh) or (1kWh = 0.145L)

We use LPG as a backup really, it's similar in cost to E7, we buy bulk LPG at 36p/Ltr  so about 5p/kwh compared with 7p/kwr for E7.  Of course conversion efficiency
play a big factor and for heating water an immersion has a high efficiency while our 30yr old LPG system boiler doesn't  Roll Eyes so I guess there's not much in it in our case.








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Justme
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« Reply #7 on: February 13, 2018, 12:07:57 PM »

Are they raw input kWh numbers?

If so then wood is wood.

1000kg of chip or 1000kg of logs contain the same kWh at the same % moisture.
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titan
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« Reply #8 on: February 13, 2018, 02:24:22 PM »

   Results are published here monthly      http://www.nottenergy.com/energy_cost_comparison/
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Sprinter
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« Reply #9 on: February 13, 2018, 03:50:48 PM »

I paid £250 for 4 cubic meters of unseasoned hardwood earlier in the year, i will need to season it for a year in our log store but it will be fine for next winter.

Also have to take down a large Eucalyptus this year and that will season for a couple of years before use, though its not necessarily free as it will cost me £500 to have felled and chopped into rounds.
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AndrewE
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« Reply #10 on: February 13, 2018, 04:14:41 PM »

Are they raw input kWh numbers?

If so then wood is wood.

1000kg of chip or 1000kg of logs contain the same kWh at the same % moisture.
I assumed it was the price as delivered, presumably more energy goes into shredding wood and forming pellets compared with splitting logs.
Also the installation costs of the systems (and maintenance costs and depreciation) might vary so much it could outweigh the price per kWhr figure.
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Countrypaul
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« Reply #11 on: February 13, 2018, 05:47:21 PM »

So with a heat pump like this, at 7degrees outside temp with a cop of 4.3 what would the figure be?

https://www.ebay.co.uk/itm/Samsung-Premium-Air-Source-Heat-Pump/391855916556?hash=item5b3c6ec60c:m:mr0_DxvDAZd8tc89q1n4yMQ

A cop of just over two in the example this chap has given doesn’t really show the heat pump in a good light. Maybe he doesn’t sell heat pumps...?

Steve

If the heat pump gives cop of 4.3 that is about twice what is quoted in the table, so the cot would be about half so £350. If it was run on E7 electric at say 7p/KWh then the cost would drop by just over half again so £175.

The problem is these are all raw figures and once you take into account all the other factors such as boiler efficiency, heat emitter efficiency, capital cost of the boiler/HP/Stove along with the heat emitters (UFH, Rads, piping etc). the raw figures that appeared so good, suddenly seem a much smaller part of the overall cost.
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RIT
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« Reply #12 on: February 13, 2018, 06:04:18 PM »

A general table like that is only going to supply some basic indication costs for anything that has to be delivered as time of year and location will have a major impact.

The best example of the issue I can give is this Which report that looks at UK LPG costs for last October.

    https://www.which.co.uk/reviews/home-heating-systems/article/home-heating-systems/lpg-central-heating

Here they are giving an 'average' cost of 12,000 kWh of LPG at £780, so far less than €1,640 for 10,000 kWh quoted in the table. My guess is that as the prices are in € the pricing is for a location with limited LPG supply, I would also say that the table has been put together by someone who supplies wood based solutions.
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Eccentric Dyslexic
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« Reply #13 on: February 13, 2018, 06:22:39 PM »

The chap posted this as gospel, generally true and indicative of what you’d expect to pay here in....France!
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RIT
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« Reply #14 on: February 13, 2018, 06:37:32 PM »

The chap posted this as gospel, generally true and indicative of what you’d expect to pay here in....France!

That's the key bit of info as it provides some location info - Very big country with lots of wood resources Smiley  It could also explain the low COP assigned to the heat pump figure as areas such as the southwest can see very low temperatures over the winter that will result in a Heat Pump being a very poor solution.

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