I think I've met my commitment, and this is how I did it.
First, some cheap and easy stuff, that'll pay for itself quite quickly.
I was already buying my electricity from Ecotricity, because they invest more of their income in renewables than any other supplier. But, they have two tariffs. The very slightly more expensive tariff is "100% green", which means that they match every unit that they supply by buying a unit from a renewable supplier, like a wind farm. I upgraded to the 100% green tariff.
To work out how to cut down electricity usage, I borrowed an electricity monitor from Lewes Library, and spent a few hours working out where my electricity consumption was coming from. We already have compact flourescent lightbulbs (cfl) throughout the house, and thought we were doing quite well in general. But, we did find two ways to make significant savings:
We watch TV through a computer. Although the computer has low standby consumption, the monitor and other peripherals weren't so good. I invested in a "Standby Saver" power strip at £21, which switches those things off when the computer is switched off. We've also started shutting down rather than putting to sleep the computer. I think we'll save at least £50 per year in electricity.
We also discovered that our microwave oven uses about 50VA on standby, but only 3 Watts. That's because it has an abysmal power factor of about 4%. It's not costing us much, because we're charged for Watt hours, not VA hours. But, it is (I think) drawing power unnecessarily, that has to be generated, even at peak times. So, we've plugged it in to a separate, switched socket, and turn it off when we can.
However, it's space heating that accounts for about 60% of domestic energy use in the UK, so this is the most important place to look for savings; by insulation to prevent loss of heat, and by efficient supply of that heat. Our space heating is mains gas, which produces less CO2 than oil, and currently less than electricity. That'll change as we remove coal, oil and gas power stations in favour of renewables and nuclear. In the long term though, electric heat pumps will probably be the most effective way of heating existing homes, and passive solar gain the best way to heat new super-insulated housing.
Second, some mid-price stuff, with big savings. It'll also pay for itself quite quickly.
Insulation: our 1950s house was already double glazed throughout, when we bought it a few years ago. Not the best double glazing, but generally in good nick, and upgrading that would be very expensive. We were amazed to find out that it didn't have cavity wall insulation, and the loft insulation was minimal. So, we used an LDC grant to help get the cavity wall's insulated for a few hundred pounds. We also upgraded the loft insulation. These measures not only kept the house much warmer in winter, but also much cooler in summer. Gone were the long, sticky, sleepless nights!
It turned out that DIY was cheaper for the loft insulation, but tricky if we wanted to use the loft for storage. So, we added 8 inches of insulation above the main bedroom, but put boards over the spare bedroom. Now, with the 10:10 commitment, we wanted to upgrade the whole loft. We've now got decent insulation throughout, under a properly boarded floor. We also had plywood sheets put under the roof, to stop dust falling through the tiles. Finally, we had a proper loft ladder, and lights fitted. The consequence is that we not only have a properly insulated loft, but much more usable loft space, in which we can keep stuff that we need to access only occasionally. For example, its much more practical to keep luggage, winter coats during summer, spare bedding, and so on - all alongside the stuff that we only ever see when moving house!
Now, all that work in the loft was quite expensive, but the insulation itself would cost only a couple of hundred pounds, save at least £100 per year on heating costs, and cuts out the worst of winter cold, and summer heat.
Third, some more expensive stuff that should pay for itself over five to ten years. Maybe quicker if fuel prices keep rising as expected.
The most important thing is that we've replaced our boiler. It was installed in 1979, and was probably about 60% efficient. That is, it wasted 40% of the gas that it burned. Modern are typically about 90% efficient. They manage this by carefully controlling the gas/air mixture, and by recovering heat from their exhaust gases.
At the same time, we chose a combi boiler, which needs no hot water cylinder. As we use an electric shower, we tend only to use hot water from the boiler for washing up and hand washing. There's no point keeping a huge tank of water hot for that. This has given us a lot of new storage space in the old airing cupboard, and on top of that, we no longer need a water tank in the loft.
And, we've also got much better heating controls. Thermostatic radiator valves (TRVs) throughout mean that no rooms become overheated. Programmable TRVs in the bedroom and living room mean we can focus heating on the bedroom in the morning, and the living room in the evening. We've also chosen a weather compensator, which measures the outside temperature, and allows the heating system to deliver the right amount of heat, at a steady rate to match the heat loss through the walls.
Finally, we picked an Ariston boiler which is compatible with solar hot water systems, and with underfloor heating (giving us a gradual route to heat pumps). Those are much more expensive systems, that we can't afford at the moment. Solar panels would have cost us much more, and saved much less energy. Heat pumps would also have cost more, and probably have saved no carbon emissions, given the current mix of the UK energy supply.
I don't drive, and we don't fly, so there's not much room for improvement there. My wife works as a rural community occupational therapist, but she's about to get a new car which should reduce her fuel consumption but at least 50%.
Now, we don't know the results yet, and they'll be somewhat weather dependent, but the new central heating system might be expected to reduce our domestic CO2 footprint by 20%. Add in the electricity savings, and we'll hope to do much better than the 10% commitment.