By rejecting all the means by which renewable electricity can be generated, the UK has set a very dangerous course

Why do those who oppose wind power insist on spoiling their case with gibberish? In his column on Friday, Simon Jenkins claimed that onshore windfarms were being planned “with no concern for cost”. But the only reason for building them is a concern for cost. If it weren’t for this issue, they would be the last option governments would choose – God knows they cause enough trouble.

As the government’s Committee on Climate Change reports, large onshore windfarms are “already close to competitive” with burning natural gas, and are likely to get there by 2020. They are the cheapest renewable sources in this country by a long way. Offshore wind costs roughly twice as much, and its costs have been escalating. After attacking the high cost of wind power, Jenkins argued that we should instead invest in “sun and waves”. The committee shows that while the expected price of electricity from onshore wind in 2030 is between 7 and 8.5 pence per kilowatt hour, solar power is expected to come in at between 11 and 25p, and wave between 15 and 31p. Talk about no concern for cost!

Incidentally, the cheapest low carbon option, the committee says, is nuclear power, at 5-10p. But, because of public objections, new plants are likely to be confined to existing sites, which means a maximum of about 20 gigawatts (a quarter of our current power capacity). Planning objections also restrict the spread of onshore wind. The only viable means of getting carbon off the grid, the committee suggests, is a mixture of sources: renewables, nuclear and carbon capture and storage.

But those who oppose wind power can’t help themselves. In parliament earlier this month, Glyn Davies, the MP who is leading the fight against windfarms in mid-Wales, insisted that “Welsh windfarms have a load factor of just 19% – the lowest ever recorded” and that “the carbon impact of the development can never be compensated for by any possible carbon benefit”. Rubbish again. The capacity factor for Welsh wind (the amount the turbines produce as a proportion of their idealised output) is 26%.

Professor Gareth Harrison of Edinburgh University estimates that the carbon payback time for the wind developments in mid-Wales will be roughly 12 months (all references on my website). Davies, like Jenkins, also claimed that “so much more” could have been done with the same money had it been spent on wave and tidal power, offshore wind and solar photovoltaics. Should MPs not be obliged to do some research before they open their mouths in parliament?

Anti-wind campaigners are also highly selective. The Campaign for the Protection of Rural Wales, obsessed by windfarms, says nothing about the opencast coalmines ripping south Wales apart. Nor do you hear a word about the destruction of the ecosystems of upland Wales (and England and Scotland) by sheep grazing. These champions of the countryside want to save it from only one threat.

For all that, it’s a real one. While the windfarms themselves divide communities, everyone hates the new power lines required to connect them to the grid. Here in mid-Wales, I have yet to meet anyone who will speak up in favour of them. Because they have to march across so much countryside, their visual impact is greater per pound of investment than that of any other technology.

Though you could see this issue coming as clearly as the pylons themselves, the green movement is completely unprepared. Greenpeace tells me “we haven’t done any work on pylons”. Hardly anyone seems to be aware of how perilous this situation is: how easily renewable energy could be killed by the power lines issue.

This is about to become a national struggle, in which opponents of the new pylons will be cast as heroes. Promising direct action, reminding us of the great battles against the reservoirs supplying England, those who marched against the new lines in Wales last week will put us, unless we act quickly, in a dangerous position. Green activists will be outflanked by green activism. The same battle will then be fought all over the United Kingdom, wherever a new power line is planned.

Many of the areas affected by proposals for new lines are either Tory constituencies or Lib Dem seats the Tories will hope to take (all of which are now contestable). It is hard to believe that the Conservative commitment to low-carbon energy could withstand a major rebellion within the party: Tory environmentalism is easily uprooted.

The greens need to decide where they stand. The only position that makes sense to me is unequivocally to support the campaign against overhead lines. Where new powerlines are built they must go underground. If they can’t go underground, they shouldn’t be built. If we are not against pylons marching over stunning countryside, what are we for?

But here too there’s a problem. Like the windfarms, overhead lines are favoured by the government because of its concern for cost. According to the National Grid, burying the lines connecting the turbines in mid-Wales to the rest of the system would cost 3.2 times as much as putting them on pylons (£562m vs £178m). But how much does that add to the cost of electricity?

Calculating this is easy (there’s an explanation on my website) – as long as you know the capital costs of the whole project. But neither the National Grid nor anyone else I’ve spoken to is prepared to hazard a guess about the cost of the rest of the infrastructure, so I can’t yet tell you whether burying the power lines makes onshore wind here more expensive than competing technologies.

In fact my efforts to obtain relevant data of all kinds from the government, the National Grid and the wind industry reveal that, like the environment movement, they are completely unprepared for this backlash. Dismayed by the collective failure to address the pylons issue, the campaign against windfarms now confidently tells the same story about this technology as others do about nuclear: the turbines are erected by big, greedy corporations; they are unfairly subsidised by the government; they will cause untold damage to human health. In view of the flack you get for supporting any power technology, I’m beginning to think it would be less controversial to argue in favour of blackouts.

So this is where the United Kingdom stands. We cannot keep burning fossil fuels without cooking the biosphere. We don’t like nuclear power. We don’t like onshore wind. We won’t like the costs of the other technologies. We reject all the means by which electricity is generated. Yet no one is volunteering to stop using it.

• A fully referenced version of this article can be found on George Monbiot’s website