6 May 2007

Microgeneration: the real costs

Bit by bit, without really planning ahead or indeed any planning at all, I seem to be becoming a strident critic of microgeneration, i.e home-baked renewable power. I criticise the government, always an easy target, for their barmy zero carbon homes scheme and their mean stamp duty tax break for zero carbon homes. Then I turn my guns on Bill Dunster, a far less comfortable target for me as I am otherwise well-disposed towards him. I spend a couple of days worrying about whether I am just being spiteful for the sake of it. Maybe I am developing blogger syndrome where everything exists merely to be shot down in flames by cynics.

So I turn to Wikipedia and to trusty Excel and I start crunching some numbers. How do all the green and not-so-green methods of generating electricity stack up?

Turns out the UK is currently consuming 350 terawatt hours of electricity per annum. That’s 350,000,000,000 kWh. If you divide it by the 65 million people in the UK, it works out at a more manageable 5,300 kWh/annum each, round about average for Europe. In comparison, the USA consumes 12,000 kWh per annum each, India just 480 kWh per annum each.

Now, just suppose you were to try to make this amount of electricity using zero or low carbon sources. How would you go about it? Ignore for the moment all the arguments about practicalities and intermittent supply and everything like that.

350 terawatt hours per annum would require either
• 14,000 giant 10MW off shore wind turbines, operating at around 30% efficiency or
• 260 million 1kW micro wind turbines, operating at 15% efficiency, (that’s roughly ten mounted on every building in the land) or
• 4,000 sq km of PV cells. That’s pretty much the size of a county like Suffolk or Hampshire. Or enough to cover the south facing roofs of around 100 million homes — there are just 25 million in the UK or
• how about 25 European Pressurised Nuclear reactors (EPRs), as being built today in Finland? Each one is designed to have an output of 1600MW.

And what about comparitive costs?

Nuclear power plants cost around £1 billion each, so 25 No. would require £25 billion to supply UK’s 350TWh/a electricity needs. What is harder to factor in is the running costs and the clean-up costs at the end of the lifespan: nuclear power is notoriously difficult to cost because of this.

Giant off shore wind turbines. Around £5 million a piece, so 14,000 would cost £70 billion in total.

Micro-wind turbines. Around £1,500 each from B&Q, so 260 million would cost £525 billion in total.

PV arrays, around £1,000 per m2. A county-full would cost around £3,500 billion.

I think my case rests. Microgeneration is ridiculously expensive, just as I thought.


  1. AnonymousMay 08, 2007

    Yes but you wouldn't buy your micro wind turbines from B&Q - they are on eBay for £1000 (imported from India), which means they probably only cost £50 or £100 to actually make!

  2. Margaret RankenMay 29, 2007

    I agree, you haven't allowed enough for the economies of scale of producing the PV cells and wind generators in these enormous volumes. A tenfold reduction in price would make micro wind turbines comparable with offshore wind, and you could expect PV cells to come down even more because they are silicon based and silicon costs can reduce a hundredfold or more with big volumes, so they could challenge nuclear once you've allowed for the clean up costs.

  3. Why does everybody seem to think that PV cells will one day become cheap? They are already being produced in huge quantities in China, and the price is currently going up, not down, because demand is high. And they are not like silicon chips: they aren't subject to Moore's Law. They won't get twice as powerful for half the money every two years.