You make good points. I wish govts in wealthy countries would offer more zero rate loans or grants to low income people to improve the energy efficiency of their homes. It's a win-win: That means low income people lower their CO2 footprint and their incomes rise. For low income people, usually that gets spent right back into the economy, further boosting GDP.

If you look closely at the heat pump rebates in the UK, it is roughly 50% the upfront cost for average installations. That leaves an upfront payment of 5,000 GBP or more. There is just no way that middle class and below will have that money in savings. A better idea: Provide zero interest loans. Whatever is saved on energy bills can be used to pay down the loan. After 10-20 years, it should payoff the entire loan with a huge benefit for everyone.