Reality Check: How many wind turbines?
To some it's cloud cuckoo land. To others, it's a big business opportunity.
The SNP target of achieving 100% of Scotland's electricity needs from renewable sources by 2020 has been met with disbelief from its principle opponents. It's also been warmly welcomed by many in the energy industry.
Two words of warning: Labour is targeting 80% of electricity from renewable energy by 2020, and it hasn't said the point between 80 and 100% at which a realistic target becomes unrealistic, and why.
Also, it's wise to treat endorsements with some scepticism.
The renewable energy industry is delighted when politicians set ambitious targets. It knows promises later have to be backed up with the regulatory, planning and pricing regimes that ensure they're kept.
So how realistic is it to aim for 100% of electricity from renewable sources?
Well, one of the more influential reports into Scotland's renewable potential came from an environment consultancy called Garrad Hassan.
This was commissioned by Scottish Renewables trade body and published last autumn.
Others have produced much less favourable reports on wind power, commissioned by those who are less favourable.
But Garrad Hassan seems to be the one that's making the running with pro-renewable politicians.
It set out different scenarios for Scotland's energy mix, including some assumptions it believes to be quite conservative.
Two of them don't seem at all conservative, in that they think the shift of home heating to electricity and to electric-powered vehicles won't make a significant increase in demand.
Their scenarios boil down to two variables making four outcomes.
One variable is the extent of renewable power generation, and the other is the extent of demand reduction.
Giving a fair wind to investment in new renewable capacity, and adding in a significant cut in energy use, the reckoning is that 123% of Scotland's energy needs could be renewably sourced, with the excess being exported.
If you're a bit less ambitious about reduction of demand for power, Garrad Hassan says its higher level of investment could deliver 106% of Scotland's needs by 2020.
With limited cuts in energy demand and a lower development of renewable capacity, it's reckoned 81% could be achieved.
And what would that mean in onshore turbines?
This is where the later stages of the Scottish Parliament election campaign have hit turbulence from those who don't like their views spoiled.
SNP leader Alex Salmond was asked how many turbines will be needed during the BBC leaders' debate in Perth.
His answer: the onshore target would be 7 gigawatts, or 7,00 megawatts, which happens to be a mere 500 megawatts behind Garrad Hassan's assumptions.
Scottish demand sits at around 6GW, but onshore wind only produces around a third of its capacity, depending how hard the wind blows, so lots more capacity would be needed.
The consultants also say their 106% figure could be reached by allying that onshore wind expansion with 13% more hydro, up to 1,700MW, offshore wind would have to grow from very little to 5,000MW by 2020.
Biomass and energy from waste would have a capacity of a further 680MW, and reach a far higher share of that capacity.
Tidal and wave power, yet to be commercially proven, are given modest ambitions of around 300MW each by 2020.
If you're not sure how that translates into onshore turbines, then consider this: According to Scottish Renewables' figures dated 18 April, there were 1,367 turbines in 117 onshore wind projects in Scotland, with a capacity of 2.4MW.
Another gigawatt, or a thousand megawatts, of capacity should be delivered from the 450 turbines under construction.
The planning process currently has 2,200 more turbines being considered, with a further 1,600 possible turbine sites being scoped for possible planning applications in future.
Total potential capacity if all that were to be developed - around 13 gigawatts, or more than double Scotland's needs.
But they don't all get approval. Garrad Hassan reckons it can assume that 26% applications do so.
For the clearest picture, it's best to go back to the installed capacity. That way, we're looking at nearly tripling the number of onshore wind turbines to reach that 100% target.
Rising power bills
Of course, none of this explains where the investment capital is to come from.
There's a telling assertion in one of the weekend newspapers that the UK government's £2bn per year tax raid on oil and gas production in British waters - the third such sudden increase in 10 years - is putting a chill on renewable investment as well.
Investment in renewable energy is based on the market signals and cross-subsidies from other forms of generation that the UK government and its regulator put in place.
Martin Falkner, energy banker at consultancy Gleacher Shacklock, told the Sunday Times: "The risk for companies is that this scale of investment will lead to rising profits just as consumers are experiencing large increases in their utility bills.
"While low-carbon investments may represent a good return for the consumer in the long run, will a future government honour the rules put in place today? The recent rise (in oil and gas tax) is a reminder that expected returns can prove illusory".
So targets can be reached - but only if there's a willingness to build a lot more turbines, on a lot more hillsides, and a willingness to fund them.