A couple of weeks ago I noticed rust on the outside of the boiler. We're on British Gas Homecare, so a gasman was dispatched with pleasing promptness, and diagnosed a leaky heat exchanger inside the boiler. That part was also covered on Homecare, and replaced within a few days. However, the rusty case is cause for concern. At the moment, the boiler is ok. But if the case rusts through, and is no longer airtight, it has to be replaced. And the boiler is sufficiently old that apparently replacement cases aren't made any more, so we are looking at a new boiler.

The house is 19 years old, and I have no reason to be believe the boiler to be any younger, so I was planning a replacement in the next few years anyway. But this is a bit sooner than planned.

I did a brief bit of research into heat pumps, as mentioned in the wonderful Sustainable Energy - Without The Hot Air by Professor David MacKay of this parishcity. A heat pump is a reverse air conditioner and is much more efficient than a traditional boiler - 300%-500% efficient, i.e. it uses much less energy to run than it moves around as heat. It runs off electricity, not gas, so converting the heating of housing to heat pumps is a step along the "electrify everything and green the electricity supply" grand plan of How To Stop Emitting Carbon Dioxide, as outlined in MacKay's book. It should also cost less to run.

Unfortunately the heat pump market is still customised expensive solutions for people with large gardens and lots of money. Too much technical information about "choices" is still presented (ground-source or air-source? heat only or domestic water too? change your radiators or not?), and too much obscure information is requested by companies before they'll quote. Why no, I don't know the area of my house in square metres, or my garden for that matter. Why can't I just give the number of bedrooms and bathrooms, as I do for getting a home insurance quote? Why aren't there easy ways to estimate the space I'd need in the garden for a ground-source pump like "about the size of two garden sheds" or similar?

Philip Pullman is promoted as a "satisfied customer" by one of the companies I contacted. That's lovely, but I am not a bestselling novelist. What I want is the easy quote for the suburban family with a small garden, but no-one's doing that yet.

Here's my free tip for someone wanting to do well by doing good: found a company that will do mass-market heat pumps, persuade the govt to subsidise installation on carbon reduction grounds, and make contracts with the big energy companies to sell to their customers, in the same way insulation has been recently. If boilers need replacing after 15-20 years, that's a lot of British people each year in the same situation I am right now.

Putting heat pumps aside, I got British Gas to send a man round to quote me for a new boiler, which happened after work on Wednesday. The chap was pleasant and low-pressure, but the cost is significantly above Which? Local price guides for the same sort of work (about 33% more). Still about half the price of the best guess I got for a heat pump. I have contact details for a couple of local companies but even the Which? Local price would blow all our emergency reserves, and then where are we if something else breaks? We just spent most of our readily-available money on windows and a fence.

More sensibly, we can save up over the next year, plan to mitigate the possibility of boiler failure during the next winter, and get a range of quotes this time next year. That gives another year for the mass-market heat pump to arrive too. Come on invisible hand, get a move on.

Professor MacKay's talk on Tuesday was about the feasibility of replacing the energy infrastructure of the UK so that we no longer use fossil fuels and emit CO2. It could be summarised as "electrify everything" i.e. cars, heating, etc and then replace the electricity generation with alternatives to fossil fuels.

To quote his executive summary:

"The electrification of transport and heating of course requires a substantial increase in electricity generation. The five plans supply this required electricity using five different mixes of the carbon-free options. The mixes represent different political complexions, including plan G, the Green plan, which forgoes both “clean coal” and nuclear power; plan N, the NIMBY plan, which makes especially heavy use of other countries’ renewables; and plan E, the Economist’s plan, which focuses on the most economical carbon-free choices: onshore wind farms, nuclear power, and a handful of tidal lagoons."

After the talk, he said in conversation (and I've confirmed this by email) that the total cost would be of the order £300 billion, plus or minus a bit depending on exactly which combination of electricity generation we went for.

Does that sound a familiar sort of number? Yes, that's the same order of magnitude as the money recently pledged by Gordon Brown to stop our economy melting down. We can stop the UK emitting CO2 for the cost of the banking bailout.

Ok, that overlooks the key difference that we'll very probably get all the bailout money back. On the other hand a nice injection of public spending on infrastructure is supposed to be a good way of getting out of recession. Also we can't spend all £300 billion at once: £5000 per person spread over 10 years begins to look almost affordable.

Doing nothing about CO2 is not a cost-free option. I'm still stuck halfway through Six Degrees, but the 4-degrees-warmer world is really pretty grim. If we do nothing about CO2 emissions, I will probably be lucky enough to die of old age before it gets very bad. Charles probably won't.

The Professor said the only other public spending on the same order of magnitude is the Iraq War. One could do an interesting compare-and-contrast about the relative benefits of the banking bailout, eliminating CO2 emissions and fighting a war in Iraq.