British Energy Demand, and Professor MacKay’s estimate of it: an explanation of the differences

Posted by – 2010/06/29

In “Sus­tain­able Energy Without the Hot Air”, Pro­fessor MacKay com­pares an energy demand of 195 kWh/d with his cal­cu­lated Brit­ish renew­able resource of 180 kWh/d, and comes to the con­clu­sion that Bri­tain can­not power itself from renew­ables. But in real­ity, Brit­ish energy demand is 155 Mtoe/y. That’s the con­firmed 2008 num­ber, from the offi­cial Digest of UK Energy Stat­ist­ics. (pdf, see Table 1.1, Final Con­sump­tion minus Non-energy use). That’s less than half the demand fig­ure used in the book, when look­ing at whether his cal­cu­lated renew­able resource is enough. When we com­pare the renew­able resource with the cur­rent demand fig­ure, we see that the resource is more than double cur­rent energy demand: and that’s before any energy effi­ciency meas­ures. And that makes a huge dif­fer­ence: by using the real fig­ure for demand, we see that the UK renew­able resource is much higher than cur­rent energy demand, so Bri­tain could com­fort­ably power itself from its own renewables.

Here at Ener­gyNum­bers, we emphat­ic­ally and enthu­si­ast­ic­ally sup­port Pro­fessor MacKay’s aspir­a­tion for an informed pub­lic dis­cus­sion about energy: and in that co-operative spirit, let’s take a look at the facts and the num­bers.

Per­haps you’re won­der­ing why the offi­cial demand fig­ure doesn’t look like the one in the book. Indeed, there are sev­eral fig­ures for demand in the book, and that’s not one of them. Let’s look at the differences.

Here we have two bars — the one on the right is our cur­rent energy demand of 82 kWh/d; to the left of it is Pro­fessor MacKay’s 195 kWh/d fig­ure for energy demand. That 195 kWh/d is presen­ted as the typ­ical demand of an afflu­ent adult: one, it turns out, with an extreme energy con­sump­tion. Such an exag­ger­ated demand has mis­lead the book’s read­ers into think­ing that Britain’s huge renew­able resource can­not meet all our energy needs. It’s very mis­lead­ing to com­pare an extreme con­sump­tion with an aver­age sup­ply. I sup­pose we could com­pare the excep­tion­ally high demand of the richest in soci­ety, with the very best sup­ply, if we we sus­pect that think that they might cut them­selves off from the National Grid to set up a “grid for the rich” (with gold-plated cables?). That’s silly. Let’s not do that. Let’s com­pare aver­age demand with aver­age sup­ply, or (amount­ing to the same thing) total demand and total sup­ply. That 195 kWh/d also includes the energy embod­ied in imports: energy which is gen­er­ated and con­sumed abroad, to make the things we import — for example, the energy involved in min­ing cop­per, or mak­ing fridges. We don’t sup­ply the energy for that assembly, any more than we provide the cop­per (not many cop­per mines in Bri­tain). We may wish to avoid being net import­ers of elec­tri­city or fuel, for stra­tegic secur­ity, but that’s com­pletely dif­fer­ent to embod­ied energy. We don’t bal­ance all our imports of embod­ied energy with match­ing exports, any more than we do bal­ance imports and exports of embod­ied cop­per, embod­ied water, or embed­ded any­thing else.

Let’s look at how our real energy demand of 82 kWh/d com­pares to the demand fig­ure of 195 kWh/d that Pro­fessor MacKay uses to assess whether we have enough renew­able resources.

Over-estimate: 73 kWh/d
Cool­ing towers and other con­ver­sion losses: 27 kWh/d
Other supply-side losses: 16 kWh/d
Effi­ciency sav­ings when mak­ing the five plans that add up: 14 kWh/d 82 kWh/d GB Energy Demand
Energy demand used when mak­ing the five plans that add up: 68 kWh/d

195 kWh/d is the demand fig­ure Pro­fessor MacKay uses when look­ing at whether we have suf­fi­cient renew­able resources (p103). But on the very next page, when look­ing at cur­rent energy con­sump­tion, he gives a fig­ure of 125 kWh/d (p104). He then takes away some of the losses within the energy industry itself, the con­ver­sion losses, which includes the huge amount of heat we waste in cool­ing towers to give 98 kWh/d (p116). And finally, when build­ing his own scen­arios, he uses a fig­ure of 68 kWh/d (p204). Those fig­ures, together with the 82 kWh/d of actual cur­rent demand, are shown to the left.

125 kWh/d is indeed the amount of power con­tained in Britain’s total fuel con­sump­tion, so that is at least a real-world fig­ure, albeit one that’s still lar­ger than our real energy demand. It’s lar­ger, because in addi­tion to our energy demand, it con­tains all the power we waste across the energy industry before it reaches the customer.

The 98 kWh/d num­ber is more rep­res­ent­at­ive of cur­rent demand. It includes demand, and some waste. After all, some energy will always get used by the power industry itself, how­ever it’s made, and although thermal plant (coal, gas, nuc­lear, bio­mass, geo­thermal) is very inef­fi­cient in throw­ing away much of the energy as waste heat, any energy deliv­ery sys­tem will have losses: for example, how­ever we gen­er­ate elec­tri­city, around 7% of it is wasted in the trans­mis­sion and dis­tri­bu­tion sys­tem. But in that 98 kWh/d there’s a lot of other waste that wouldn’t need to be gen­er­ated in a decar­bon­ised Bri­tain, such as energy use by oil refiner­ies. So both of those fig­ures reflect the inef­fi­cien­cies built into the way we cur­rently gen­er­ate our energy, and neither are rep­res­ent­at­ive of demand within our future low-carbon society.

Our cur­rent energy demand of 82 kWh/d would be reduced by about 9 kWh/d simply by elec­tri­fy­ing cars. That and other mod­est energy effi­ciency meas­ures give us us Pro­fessor MacKay’s tar­get demand of 68 kWh/d. There are lots of oppor­tun­ity for other energy effi­cien­cies in there, but also the pos­sib­il­ity that rising incomes will cause energy demand to rise.

In con­clu­sion, to assess the poten­tial of Britain’s renew­ables, as well as to set a fig­ure for build­ing a plan that adds up, any­where in the range 46 kWh/d to 80 kWh/d would be reas­on­able — it’s a ques­tion of how much money is inves­ted in energy gen­er­a­tion, rel­at­ive to the amount inves­ted in energy effi­ciency. In con­trast, the arti­fi­cially inflated demand fig­ure of 195 kWh/d is nowhere near our real energy demand, and has mis­lead people into believ­ing the myth that Britain’s energy demand exceeds its renew­able resource, whereas the reverse is true: our renew­able resource is much greater than our energy demand.

7 Comments on British Energy Demand, and Professor MacKay’s estimate of it: an explanation of the differences

  1. New:: Brit­ish Energy Demand, and Pro­fessor MacKay’s estim­ate of it: an explan­a­tion of the dif­fer­ences

  2. Patrick Stewart says:

    To be fair, that com­par­ison on page 103 is between his two ball­park fig­ures based on back of an envel­ope estim­ates. His actual con­clu­sions on what is and isn’t pos­sible are much later in the book (page 203 onwards), but as you seem to half-acknowledge above, on the fol­low­ing pages (104 and 107) he com­pares both of these estim­ates to offi­cial fig­ures. He finds that he over­es­tim­ated con­sump­tion by about 50% as com­pared to the same DTI fig­ures you’re using except from 2006 rather than 2008; mostly by includ­ing the energy used to make things that isn’t expen­ded in the UK. So pretty much your entire art­icle is already in the book. He uses those cor­rec­ted fig­ures, with fur­ther reduc­tions due to effi­ciency, in the rest of the book, includ­ing in his actual con­clu­sions.
    What you haven’t writ­ten about at all is that he also finds that his total renew­able energy poten­tial estim­ates were very optim­istic, about 3–10 times higher than sim­ilar estim­ates by sev­eral other groups.

    I don’t really know why I’m post­ing this, you’re clearly already aware of it, it’s in you graphs; I just can’t under­stand how you can com­plain about Mackay inflat­ing his fig­ures while also being aware that they’re lower than yours in his con­clu­sions on pg 204. If you actu­ally read the text on page 103 it clearly says “Now we will see if these estim­ates are cor­rect”, not “so here I have con­clus­ively proved renew­ables are insufficient”

  3. admin says:

    Hello Patrick,

    I seem to have failed to get the gist of the piece across to you, which is a shame. I’ll try to phrase it dif­fer­ently. Let me know if this helps.

    The num­bers in the first third of Pro­fessor MacKay’s book all lead to the con­clu­sion on page 103 that even if we used all of our renew­able resource to its tech­nical max­imum, ignor­ing eco­nomic, social and envir­on­mental con­straints, then it is not enough to meet our energy demand. And that (as he writes later in the book) this applies to Europe too — he writes: “Europe, like Bri­tain, can­not live off its own renew­ables”.

    And yet the fig­ures on 103 are wrong — we all agree on that — you, me, David, the offi­cial stat­ist­ics. So any con­clu­sion based on them must be in doubt.

    Indeed, there are plenty of reas­ons for doubt — because in addi­tion to the inflated demand, the first third of the book also con­tains eco­nomic, social, and envir­on­mental con­straints on sup­ply, des­pite the state­ment to the con­trary (I’ll write a bit more about the sup­ply side in a new art­icle, later). So those are not about the phys­ics of the thing at all — they’re opin­ions. So, we have an inflated demand, and a set of polit­ical opin­ions on sup­ply. That’s not (in Pro­fessor MacKay’s words) “what the laws of phys­ics say about the lim­its of sus­tain­able energy”.

    As it turns out, Britain’s renew­able resource is an order of mag­nitude higher than our energy demand.

    And so Bri­tain, (just like Europe and the whole world) can get 100% of its energy from renew­able resources.

    Now, as that’s fun­da­ment­ally dif­fer­ent to Pro­fessor MacKay’s con­clu­sion, I think it’s pretty import­ant. Because it means that we have very real choices about the next 40 years. We can choose nuc­lear or CCS as trans­ition tech­no­lo­gies if we want — but we don’t have to have either of them. They are only options, not necessities.

  4. […] claims that the UK’s energy demand fig­ure is 195 kWh/d – but the true demand fig­ure is 82 kWh/d and can be read­ily reduced with effi­ciency meas­ures and EVs. There­fore the UK can quite real­ist­ic­ally be powered by 100% renew­able energy – even using […]

  5. Robert says:

    Good piece Andrew. And please also see:

    Shock: “Food sup­ply could blot out coun­tryside, warns gov­ern­ment sci­ent­ist” >

  6. […] of “school boy” errors, both in terms of over­es­tim­at­ing the UK’s energy con­sump­tion (see here), pre­pos­ter­ously sug­gest­ing Uranium from sea­wa­ter as a plaus­ible energy option (debunked by Barti […]

  7. Kevin Graham says:


    The link to ‘Digest of UK Energy Stat­ist­ics’ is broken — it has been moved to — would you be able to update the link?


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