Nellie the problem is, not the power taken from the grid to maintain wind turbines when they are switched off for servicing. I doubt anyone would argue with this, the real cost is the large amount of back up facilities that have to be maintained to deal with the fact that windpower is undependable and uncontrollable.
According to Renewable UK there is 10,000Mw of installed windpower capacity in the UK, somewhat more than I had realised. If we assume that, allowing for maintenance and downtime 8,000Mw of this power is operational, it is only operational if the wind blows. Well, on one cold day in February when power demand was at its highest the whole UK stock of wind turbines on and offshore could only produce 29Mw of power - and there are probably a significant number of days when production is below 1000Mw.
This means that the windpower capacity of the UK has to be backed up by an equal capacity of conventional capacity that has to work in a polluting energy and money wasteful way to support our wind industry.
Why polluting and wasteful? Because the government's answer to this back up problems is
1) to pay hundreds of million of pounds every year for diesel back up facilities all over the country that can fire up, using diesel, a fuel far more polluting than gas, and not covered by emission control standards, when ever required. One wind power company has diesel generating equipment on a site beside far more efficient and less polluting local gas-fired power station four miles from my home.
2) to pay equally large sums to conventional power stations to keep generators warmed and ticking over so that they can reach full power almost immediately it is asked for. This is because under normal circumstance large generation equipment needs to take several hours to gently warm up before it is possible to push the lever to 'full power ahead'. Over a year a power station may need to have at least one generation set on standby for a total of months, consuming fuel, making emissions but crucially making no electricity and earning no money in order to be ready to respond the moment the wind turbines stop turning, that or blackouts. Quite reasonably the generators expect to be paid for the fuel, manpower and maintenance needed to keep their generation equipment in this state.
Sorry this is so long but few people realise the dirty polluting back story to 'clean' windpower.