‘So, as Rishi Sunak has announced that we’re now allowed to keep installing new gas boilers till 2035, and they last about 15 years, that means I’ll be able to keep a gas boiler till 2050, so I might even be allowed to die with a gas boiler still going in my house, and may never have to switch to an ugly, expensive air-source heat pump which makes an annoying fridge-like hum in the garden, vibrates through the bedroom wall and keeps the house at a weird, lukewarm temperature all day and night.’

I think many of us were making that kind of calculation last month. Were we tempted by Sunak’s raised offer of a government grant of £7,500 for switching to a heat pump, up from £5,000, to reward us for doing our bit towards net zero? I don’t think so. The grant doesn’t get close to covering the full cost. You don’t even get the grant until the expensive work is completed, and the paperwork is a 12-hour job in itself, requiring a valid EPC certificate with ‘no outstanding recommendations’ for improved cavity-wall, window or roof insulation. So you must also spend a fortune on sealing your house from all possible draughts. Even my most eco-minded friends have not yet installed a heat pump. The government policy for Britain to install 600,000 a year from 2028 has a long way to go. At the moment, the rate is just 70,000 per year.

I asked my plumber whether I should consider a heat pump for my small Victorian end-of-terrace house, and he shook his head. ‘It would mean sealing all your windows and doubling the size of the radiators. We do install heat pumps, but we need our customers to know the truth. I don’t think they’re the future, to be honest. I think new technology will come along, involving hydrogen with just a bit of gas.’

I chatted to a friend in Kent who’s in the middle of heat-pump hell. Hers was installed by a firm in Essex. It worked bearably at first, although it only heated the house to 16 degrees so they had to wear jerseys, and the water was only just hot enough for a bath. But after its first service, ‘it started making the most dreadful noise, as if it was about to explode’. The installer blamed the maker, the maker blamed the installer, there was found to be ‘air in the system’, the refrigerant had leaked out and the pipework hadn’t been properly insulated. With the installer and manufacturer still stuck in a cycle of blame, my friend has been without a functioning heat pump for six months. She is now reliant on her wood-burning stoves, her immersion heater and her oil-powered Aga for back-up.

Alan in a semi in central England, meanwhile, is being driven mad by the tonal hum from his neighbour’s heat pump mounted on the adjoining wall. ‘The noise emanating through the cupboards and walls into my bedroom, a low hum, can be ruinous,’ he tells me, and he dreads the moment at 6.30 a.m. when the neighbours turn up their system to run their hot water. Alan is nervous about making a noise complaint to Environmental Health because if you do, and you then want to sell your house, the noise complaint must be declared, and this will severely jeopardise the sale.

Do you get lower electricity bills if you replace your gas boiler with a heat pump? No, says the sceptic Andrew Montford, director of Net Zero Watch, who’s written a paper re-debunking every ‘debunking of heat-pump myths’ in the heat-pump zealot Jan Rosenow’s paper on the subject; a mini-war is taking place online. ‘You get a free kw/h of heat for every kw/h of electricity you put in,’ he explains to me, ‘but what you’re not told is that electricity is four times the price of gas, and will go up again because wind farms will steadily make the grid less efficient.’

Are they about the same size as an air-conditioning unit? ‘No – mine is much larger,’ says Alex in west London, who has refurbished her house at vast expense, with underfloor heating on all floors, and has hidden the heat pump behind the studio at the far end of her 80ft garden because it’s ‘as large as a chest freezer’, and needs to be out of doors so that the air can circulate. But she is pleased and proud to be doing her bit to save the planet.

Armed with these endorsements of my heat-pump scepticism, I then chatted to two heat-pump zealots and found my scepticism beginning to founder. Well, not at first, when Mark Hewitt, who runs a company installing heat pumps, gave me the full ‘wild fires and floods in Greece’ lecture (‘This is what we have brought upon ourselves by combusting gas’). But then he explained that, actually, you don’t need to enlarge your radiators (‘You might just need to improve your rattly, leaky windows’) and that a heat pump can be small, and quiet, and in fact ‘works beautifully, as beautifully as a fridge’, which is ‘an amazingly stable piece of technology, the most reliable domestic appliance’. That’s true – about fridges.

‘But heat pumps are ugly and I don’t want one in my small garden,’ I plead. ‘Ugly!’ he replies. ‘Cars are ugly. Bins are ugly. But we live with those.’ True enough. Installing a heat pump, he says, is the one big thing I can do in my life to address carbon. ‘But is it true I’ll need to close my bedroom window at night? I like a cold house at night and hate the idea of “keeping the heat pump on a lukewarm setting 24/7”.’ ‘The theory that you have to keep all the windows closed is pure propaganda,’ he said, but admitted heat pumps do work best if they’re kept on all the time.

Christoph Grossbaier, who runs a firm installing heat pumps, tells me they double up as air-conditioning units. He also softens me up with the suggestion of starting out with a ‘hybrid’ model: install a heat pump, but keep your gas boiler so you can top it up. The only problem with doing this is that you forfeit your right to the government grant.

Even if I were offered a heat pump totally free of charge, I’d still have a dilemma. Is a slightly more annoying and less effective heating system worth the genuine glow of good citizenship it would bring? I’m not sure which way I’d jump. But when this would cost years of savings, for a technology that might soon be superseded, I’m not going to be one of the government’s hoped-for 600,000 installers.