“GREEN is good,” declared Boris Johnson as he unveiled his much-anticipated £5,000 scrappage scheme for gas boilers. This was met with instant derision, not just for his paraphrasing Gordon Gekko, but because the scheme will only help finance 90,000 heat pumps in England and Wales.

So what is the Scottish Government offering instead? “I am not aware of any grant in Scotland”, said SNP MP Stephen Flynn on BBC's Politics Live yesterday. Well, perhaps he should have a word with the Scottish Government, who told me we can get all £7,500 here per heat pump. Yah! Puts Boris in his place.

However, the Scottish Government heat pump scheme isn't quite as generous as it sounds. Only £4.5 million was offered to finance it when it was announced in November 2020 by Scotland’s Energy Minister Paul Wheelhouse. That's – what – about 5,000 heat pumps at £10,000? 2 million Scottish homes are heated by gas. So perhaps Mr Flynn was right to forget about it.

Patrick Harvie, the Scottish Zero Carbon Minister, is only offering £1.8 bn over the next five years for the entire Scottish Heat and Buildings Strategy. But decarbonising one million Scottish homes by 2030, which seems to be the plan, will cost at least £33bn. And since the Scottish Government is not going to put the money up, it will be home owners who pay the cost – on top of the £500 extra they could be paying for energy bills next year.

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So, will I be grabbing this £7,500 heat pump bounty before it's gone? Perhaps not. I live in a tenement flat built over a century ago with high ceilings and all the insulation qualities of a tent, even though it has double glazing. Heat pumps might work if you live in a modern, semi-detached in an English housing estate but in Scotland? With our housing stock? And our weather?

Heat pumps require a high level of insulation. Scotland's tenements are draughty for a reason: they need to breathe or they become rotten with damp. Open fireplaces were supposed to do that back in the days of coal.

Anyway, to work in multiple occupancy buildings heat pumps really need to be installed for whole blocks, according to experts like Dr Jan Rosenow of Sussex University. This means complex agreements between private owners and tenants. I can almost hear the cowboy heat-pump engineers rubbing their hands as I write.

But let's not be negative. This could be an ideal opportunity for the new Nat-Green Scottish Government to make a step change in decarbonising home heating, which accounts for 20% of our emissions. They could re-engineer our energy use by introducing city-wide district heating, like in those Scandinavian countries, to which Nicola Sturgeon has always compared Scotland.

Two thirds of Denmark's homes, 1.7 million, are served by district heating. Networks of pipes distribute heat underground to blocks of flats or sometimes individual houses. This can be highly efficient since one big central heat source replaces individual boilers in each home (or in many Scandinavian cases wood burning stoves, which also have to be scrapped). However, district heating presents formidable engineering challenges laying potentially hundreds of miles of large, insulated underground pipes.

Metering is a problem too. Most city-wide district heating schemes, such as in the Latvian city of Riga, date from the communist era, when energy was supplied free to city blocks. It seemed like the socialist thing to do. Unfortunately, this led to people regulating the heat of their apartments by opening the windows, causing huge waste. So, hot water and/or hot air have to be metered and billed in every apartment to regulate demand. This is not impossible but adds cost.

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Also, the heat has to be generated somewhere. Ideally, district heating uses the waste heat from power stations, like Torness in East Lothian or Hunterston in North Ayrshire, which produce some 40% of our energy (when they're working properly). These nuclear power stations are, for obvious reasons, placed some distance from population centres – and anyway are being phased out. The wind-turbines that are supposed to replace them don't produce waste heat in quite the same way.

This would suggest that we need city-based power stations, or "combined heat and power", generating hot water locally from renewable electricity. Perhaps the new Small Modular Reactors being developed by Roll Royce, that Boris Johnson is so keen on, might be ideal local power sources. No, only joking. Somehow I don't see the residents of Kelvinside or Edinburgh's New Town agreeing to have a portable nuclear power-station round the corner. The Scottish Government has anyway banned nuclear power.

Biomass might be an alternative, in theory, but many environmentalists are unsure that burning wood pellets on an industrial scale is very green. It releases more CO2 than gas and would require carbon capture and storage to deal with the emissions. Which brings us back to where we started with coal, oil and gas – all of which are forbidden.

Let's be honest. Neither Boris Johnson nor Nicola Sturgeon has the remotest idea how to achieve a 75% reduction in CO2 emissions by 2030. The UK Government at least has a plan for generating energy since it is going to build more nuclear power, but Scotland has rejected that route. There is a reasonable chance that heat pumps will become a cheaper in England given economies of scale. But the mass installation of heat pumps is unlikely to be a solution in Scotland, even if there was the electricity to power them.

We could theoretically be self-sufficient in wind energy with a bit of hydro and biomass, but there is little prospect of that happening by 2030. As this summer demonstrated, the wind doesn't always blow. And this green homes revolution is supposed to happen in the next 8 years – just as the Scottish Government is phasing out petrol and diesel cars. The Scottish energy gap is now yawning very wide.

We can only assume that Nicola Sturgeon will not be around to honour the promises being made in her name. They look like a pig in an environmental poke.

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