One of the things about governments is that when faced with a complex issue they grasp a simplistic quick-fix solution which makes things worse.

Cars are producing too much CO2, let’s all go diesel; oops.

In Scotland, as elsewhere, residential rents are rising so the Scottish Government introduces a rent cap. The result is a reduction in the supply of houses for rent, in some places you cannot now rent a home.

Since its reverse takeover of the Scottish Government, the Scottish Green Party has been working hard to increase our cost of living, damage the economy and make our public services harder to fund.

After helping muck up the housing rental market and flushed with righteous indignation over the self-inflicted fiasco of the Deposit Return Scheme, the Greens are finally getting to grips with the area they most want to meddle in: energy policy.

We need to use much less fossil fuel heating our homes if we are to meet our goal to limit global warming. What we cannot do on the way towards that worthy objective is to increase dramatically the cost for people to heat their homes, nor must we increase the vulnerability of our energy supply.

Patrick Harvie has decided that when it comes to delivering heat to our homes the only solution is heat pumps. A nice simple solution to a complex problem - effective, cheaper to run and green, heat pumps seem to have all the answers. Well done, Patrick. Except that the merits of heat pumps are not as straightforward as they seem.

Read more: Thanks, First Minister, for letting us know what we're in for

There are essentially two types of heat pump, ground (or occasionally water) source and air-source. Their first drawback is that they are both more expensive, in the case of ground source much more expensive, to install than gas boilers. There is therefore an extra cost for householders or taxpayers.

Some claim the upfront cost is not a problem because heat pumps are cheaper to run than gas boilers. Unfortunately, that’s not true. The efficiency of a ground-source heat pump means it has got a decent chance of being cheaper to run than your gas boiler - but having cost potentially more than 10 times as much to install it is a challenging equation for the bill payer. The bigger problem is with air-source heat pumps, which make up the vast majority of all heat pump installations. Broadly an air-source heat pump should on average produce three units of heat for every unit of electricity it consumes. Gas is about three times cheaper than electricity but the efficiency advantage for heat pumps makes it sound like running costs would be comparable.

Unfortunately, the deadly words in this analysis are “on average”. If you look at the efficiency of a heat pump through the year as a whole an average efficiency ratio of three is realistic but this ignores the fact that in July, when heat pumps are most efficient because the outside air is warmer, we don’t need much heat, but in January when we need a lot of heat an air-source heat pump’s efficiency ratio might be only one. Based on how we actually use our heating systems an air-source heat pump will be more expensive to run than a gas boiler.

Another issue is that our energy distribution network could not cope if there is rapid widespread switch to heat pumps. This can be fixed but it will take time and cost many billions of pounds which somebody has to pay for.

Worse still, the Scottish Government is allowing our electricity generation capability to become less and less suited to heat pumps.

Heat pumps need, surprise surprise, reliable supplies of electricity. Hydro- electric generation is great but small, wind is useless because of its intermittency, batteries work for a few hours not days; only fossil fuel and nuclear can be relied on.

If Scotland were a separate country when the Torness nuclear power station goes off-line we would be stuffed.

A key issue with air-source heat pumps, as Lord Haughey has pointed out, is that they can struggle to work in Scotland - you might be chilly in your home on a cold winter’s night. New well-insulated houses with underfloor heating are fine but in Scotland the vast majority of homes are not like that and because heat pumps heat water up to lower temperatures than gas boilers that’s a problem. Much larger radiators, wall insulation (which can create damp and mould risk) and other measures help manage the problem but add another layer of cost.

There are solutions.

For the home where a ground-source heat pump is impractical a hybrid system where an air-source heat pump is topped up when necessary by a small gas boiler is a solution which works and is available now. As more renewable energy generation comes online electricity tariffs will increasingly widen the price difference between peak and off-peak power; good old storage heaters may then make a comeback. The potential role of hydrogen should also not be ignored.

On the supply side there is only one sensible decision. We have got to invest in at least two nuclear power stations to replace Hunterston which is already off-line and Torness which has not got many years to go. Without that, within 20 years, we will be worrying about our ability to keep the lights on and, ironically, we will be crucially dependent on England’s nuclear generation.