Making sense of LPG running costs £/kWh calculation {Merged} 15 May 2020 at 10:46AM edited 15 May 2020 at 1:06PM in LPG, heating oil, solid & other fuels 12 replies 205 views

simpjd

Hi,
Was hoping someone could help me understand where I'm calculating this wrong.
I'm trying to figure out the £/kWh of LPG.
Many references on the internet state around £0.07/kWh (7 pence) for LPG, which sounds reasonable.
However, the average cost per litre of LPG is around £0.50/l, which is around what we pay.
  - 1 litre of LPG / 3.85 = 1m3
  - so 1m3 of LPG = £1.925 (based on £0.50/l)
  - 1m3 * 1.02264 (correction factor) * 46 (LPG calorific value) / 3.6 (conversion) = £/kWh
  - so 1m3 = 13kWh
  - £1.925 / 13kWh = £0.1471/mWh
£0.1471/mWh is more than double £0.07/kWh......??!? So where is my maths going wrong?!

bobmac62

You are paying way too much for your LPG, presumably bulk? Current price is around 30p per litre.

simpjd

Thanks for the response! I just called up Calor our current provider, best they can do they said for 36 month contract is 40p/l. Still a 20% improvement based on my current price (amazing what a phone call can do!) however not as good as your 30p/l! Can you recommend a supplier? We use around 8,000l a year in a 2,000 tank.

Flt._Lt._Biggles

simpjd said:

Hi,
Was hoping someone could help me understand where I'm calculating this wrong.
I'm trying to figure out the £/kWh of LPG.
Many references on the internet state around £0.07/kWh (7 pence) for LPG, which sounds reasonable.
However, the average cost per litre of LPG is around £0.50/l, which is around what we pay.
  - 1 litre of LPG / 3.85 = 1m3
  - so 1m3 of LPG = £1.925 (based on £0.50/l)
  - 1m3 * 1.02264 (correction factor) * 46 (LPG calorific value) / 3.6 (conversion) = £/kWh
  - so 1m3 = 13kWh
  - £1.925 / 13kWh = £0.1471/mWh
£0.1471/mWh is more than double £0.07/kWh......??!? So where is my maths going wrong?!

Are you sure the calorific value of LPG is only 46?

Flowgas suggests it is 95
Calor says it is Propane 95 MJ/m3 & Butane 121 MJ/m3

simpjd

Also back to the maths, based on 30/p a litre, it would be much closer but coming out at 8.8p per kWh. Whereas "apparently" UK average for LPG is 7p per kWh.

Unless my maths is wrong (please question it!) it would require an LPG price of 24p/l......is this realistic for anyone in the UK?! ....or is my maths wrong....

Flt._Lt._Biggles

simpjd said:

Thanks for the response! I just called up Calor our current provider, best they can do they said for 36 month contract is 40p/l. Still a 20% improvement based on my current price (amazing what a phone call can do!) however not as good as your 30p/l! Can you recommend a supplier? We use around 8,000l a year in a 2,000 tank.

There's a sticky thread above that discusses bulk prices of lpg

simpjd

Very interesting!! I got my source from Wikipedia....know for its accuracy...haha!

"LPG is composed mainly of propane and butane, while natural gas is composed of the lighter methane and ethane. LPG, vaporised and at atmospheric pressure, has a higher calorific value (46 MJ/m3 equivalent to 12.8 kWh/m3) than natural gas (methane) (38 MJ/m3 equivalent to 10.6 kWh/m3), which means that LPG cannot simply be substituted for natural gas."

Mister_G

simpjd said:

Thanks for the response! I just called up Calor our current provider, best they can do they said for 36 month contract is 40p/l. Still a 20% improvement based on my current price (amazing what a phone call can do!) however not as good as your 30p/l! Can you recommend a supplier? We use around 8,000l a year in a 2,000 tank.

Price will depend where you live.  My local independent supplier in Hampshire is currently 33ppl.  When does your contract expire?  Until it does, you wont be able to shop around. Normal contracts are 24 months, not 36 months.  No doubt Calor wont fix it for 36 months.

Mister_G

Try here:
https://nottenergy.com/resources/energy-cost-comparison/

simpjd

Contract actually expired 12 months ago (!) so I'm free to change. No they said 36m contract 12m fixed, 24 variable. In your experience is it better to find small independent over large national?

Flt._Lt._Biggles

simpjd said:

Very interesting!! I got my source from Wikipedia....know for its accuracy...haha!

"LPG is composed mainly of propane and butane, while natural gas is composed of the lighter methane and ethane. LPG, vaporised and at atmospheric pressure, has a higher calorific value (46 MJ/m3 equivalent to 12.8 kWh/m3) than natural gas (methane) (38 MJ/m3 equivalent to 10.6 kWh/m3), which means that LPG cannot simply be substituted for natural gas."

Looks like a typo.
The sentence you quote has no citation.
But earlier in the wiki article it states (with a citation):
"LPG has a typical specific calorific value of 46.1 MJ/kg compared with 42.5 MJ/kg for fuel oil and 43.5 MJ/kg for premium grade petrol (gasoline).[8] "

As 1kg of propane is about 0.5m3 of gas, a calorific value of 95 MJ/m3 is about right.