Can you guess how many tonnes of CO2 Pure Planet Members have saved in a year?

  • 18 September 2018
  • 7 replies
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  • Community Manager
  • 7587 replies
Give yourselves a pat on the back!

In our first year you guys have prevented 14,145 tonnes of carbon dioxide from going into the atmosphere by choosing 100% renewable electricity.

We’ve also offset 43,667 tonnes of carbon dioxide to account for the gas we’ve supplied on behalf of our Members on dual fuel supply.

Here’s what these carbon savings actually mean:



All that in only a year! Amazing :heart:

7 replies

Userlevel 7
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hi Marc
how did you calculate those figures? (you knew I'd ask!)

I may be off the mark here (no pun intended), but using a figure of .35156 tonnes per MWh for the Electricity (which is the 2017 UK gov. figure), dividing this into 14,145 this equates to 40,235MWh, call it 40,000Mwh

Obviously you haven't had a constant number of users for the year, but if you had and you used a presumed average of about 4000kWh (which lies between ofgem's medium and high user amounts, and makes the calculation very easy) =4Mwh/customer that would equate to 10,000 customers (if it was constant over a year but since I have no idea of your growth rate over the year I'll assume for the moment it doubled, in which case lets say it started the year at 6600 and ended at 13,200, that would (sort of) average out at about 10000

Am I on the right track or have I made some ridiculous errors or assumptions or dropped the odd decimal...

I've only looked at the electricity, the gas is much more complicated, I tried a similar calc on that but it gave more customers (14,000) for gas and there must be fewer so I knew it was wrong. How do you offset the CO2 for gas?
Userlevel 7
Badge +9
This is a much more complex calculation than 5am will allow.i may do it later.
The way i see the maths is that this is based on a set period of time therefore customers who joined half way into the year would only of used 2000kwh.so you need to factor growth rates and % of annual usage pro rata.I.E.

Wk1 10 new customers 40000 kwh total use
Wk2 20 new customers 78400 kwh total use
Wk3 30 new customers 115000kwh
Ditto
Ditto
Wk52 520 new customer 40000kwh.
Does this even make sence. I need more sleep its way too early.
Userlevel 4
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Hi @woz, @Jon1

I love how there's such an early morning interest in saving some CO2! I'm not such an early bird, but now that I've had my morning coffee I'll jump in with some numbers.

We've assumed that every Member has switched to us from a non-green tariff. (Presumptuous I know, but reasonably accurate.) The average UK fuel mix is about 29% renewable, so we haven't included these carbon savings. Hopefully this partly explains why it's less than you were expecting.

The UK average carbon content for electricity is 225g/kWh
https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/737451/fuel-mix-disclosure-data-2018-revised-2.pdf

So by using all renewable sources, we've saved the CO2 generated by the other 71% of sources.

If you back calculate it, it gives us about 15,000 Members. As @Jon1 is right to point out, it is cumulative - so our handful of Members at the start doesn't really make a dent compared to the number of new Members last month. Our rate of growth is increasing, but it will be a few months before this is really reflected in our carbon savings.

I've used the figures from the quantity of energy we've bought, rather than the more laborious method of pulling data for usage and time with Pure Planet for each Member.

In going back through my numbers, I've realised I've used a lower figure for gas than I should have done. If I update the figure to 357g/kWh for gas, we're carbon offsetting a massive 69,285 tonnes of CO2 in our first year. Thanks for helping me spot this! I'll now update the blog.

Hope this all makes sense, I'm more than happy to clarify if not. What other number based stats would you like to see?

- - - Updated - - -

Here's the updated infographic:

1107
Userlevel 7
Badge +11
hi @Jon1 and @Laura
jon I think our body clocks are 12 hours apart!
I had to make many assumptions but we are both in the ballpark (so to speak) and that's sort of what I did. Effectively we are both doing the same calc a different way.
My calcs for gas came out at 14000 so I knew something was wrong as it should have been fewer users than for electric, but then I'd had to guess growth rate.
Laura how is the carbon offset for gas calculated? What does the 357g/KWh (or 0.357Tonnes/MWh) assume?
Userlevel 4
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Hi @woz

Sorry for the radio silence. I've been doing a lot of reading of government published reports to find the correct answer for you.

The carbon emissions per kWh are based on the calorific value of natural gas. By knowing how much energy is in the methane, it's possible to figure out how much carbon dioxide will be produced. Simply put, as we know the ratio of the elements involved in combustion, we know how much CO2 is produced per unit. If you're chemistry minded: CH4 + 2 O2 -> CO2 + 2 H2O + energy

This research has thrown up another figure, (my final answer for this, I promise), which is 183g/kWh. It's not simple feat to get to the bottom of this data, but I can only apologise for muddling this up earlier. In terms of the actual carbon offsets bought, this is the figure we've been working with. We'll be talking the specifics of the carbon offsetting projects we're supporting soon.

This is where the figure is from: https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/715425/Conversion_Factors_2018_-_Condensed_set__for_most_users__v01-01.xls


- - - Updated - - -

Here's the final version of our carbon offsets:

1123
Userlevel 7
Badge +11
Now I liked a bit of the ole blue flame Bunsen burner in Chemistry O level at school 😂😂😂, Laura, but this is way way way over my head 🤓🧐! Congrats on your perseverance 👏👏👏👍👩*🎓
Userlevel 7
Badge +11
Hi Laura
Thanks very much for the reply, interestingly your final answer? (although you still have 50/50, phone a friend or ask the audience) is more or less what I assumed in my original calc but then I did use the same source as you so not really a surprise.
CO2 offset for Gas is harder to calculate because as you say you have calorific value (not a huge variation) and generation source to consider, and that's before you even think about how it's transported.
Mind you electric isn't that easy either, there is also loss in the transmission system which means that more CO2 is produced for less Mwh out.
Of course the same transmission losses occur when you're generating from renewables, but all that means is you use more renewables..

hmmm... I suppose we have to trust the government boffins' figures are correct then...
Keep up the good work, less is more!

LauraS;12168:
Hi @woz

Sorry for the radio silence. I've been doing a lot of reading of government published reports to find the correct answer for you.

The carbon emissions per kWh are based on the calorific value of natural gas. By knowing how much energy is in the methane, it's possible to figure out how much carbon dioxide will be produced. Simply put, as we know the ratio of the elements involved in combustion, we know how much CO2 is produced per unit. If you're chemistry minded: CH4 + 2 O2 -> CO2 + 2 H2O + energy

This research has thrown up another figure, (my final answer for this, I promise), which is 183g/kWh. It's not simple feat to get to the bottom of this data, but I can only apologise for muddling this up earlier. In terms of the actual carbon offsets bought, this is the figure we've been working with. We'll be talking the specifics of the carbon offsetting projects we're supporting soon.

This is where the figure is from: https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/715425/Conversion_Factors_2018_-_Condensed_set__for_most_users__v01-01.xls


- - - Updated - - -

Here's the final version of our carbon offsets:

1123


- - - Updated - - -

Chemistry lesson...

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