Somewhere upstairs, my wife is sitting in bright light beside a warm radiator, sipping tea, flicking through glossy magazines as she blow-dries her hair, and consuming in 30 minutes about half the energy used by the typical Bangladeshi all day. And I’m trying to make up for that. I’m sitting in the dark. The heating is off. I’m wearing two jumpers, a hat and a scarf and a pair of fingerless gloves I improvised out of old socks that had gone at the ankle. I’m writing this on an ancient manual typewriter. It’s not easy. Unlike a computer, it doesn’t let you move blocks of text around, and there’s no word count. You can’t switch to the internet to look something up. It’s also bone-shakingly hard work, a bit like a workout at the gym.

But I’m enjoying myself. There is no junk e-mail. And I’m extremely happy to think of all the electricity I’m saving. Because recent calculations suggest that IT will very soon overtake aviation as a guzzler of energy. All these videos on YouTube and unread blogs take up space on servers that suck ever-increasing amounts from the grid. An avatar on the online game Second Life uses as much energy as the average Brazilian.

Then there are all the gadgets we can’t seem to live without. All the batteries that need recharging. In fact, it was the batteries going on my mouse that got me thinking about using this typewriter. Now I’m planning to de-escalate my digital life altogether. Out with the computer unless strictly necessary, in with the typewriter. Out with the Palm Pilot, in with the paper diary.

The planet is heating up, the weather turning ever more unpredictable. Forests are dying, and animal species too – at such a rate that it’s been described as the sixth great extinction (or was it the fifth? If I were online, I could look it up).

On top of that, it is now accepted that world oil production will peak in as little as three years, if it hasn’t already, and go into terminal decline.

For both these reasons it is imperative to save as much energy as we can – reducing emissions and preserving valuable fuels to help make the transition to a renewable energy infrastructure. And to do this we need a target. James Hansen, the Nasa scientist who has done so much to raise the issue of global warming, argues that we should focus on the safe level of CO2 in the atmosphere – 350 parts per million. He may be right, but it doesn’t work for me. More helpful is research from the Swiss Federal Institute of Technology that identifies the energy use each of us must stick to if we’re to keep the planet hospitable: precisely 2,000 watts.

As a rate of consumption, 2,000W would keep a two-bar electric fire running constantly, or 20 not-very-eco incandescent light bulbs. (Or, if you prefer, it’s the power you’d get from 22 humans trudging endlessly on a treadmill.)

Watts are like the rate at which water flows out of a tap. The total energy used is measured by timing the flow (how long the tap has been running at that rate). This gives the total amount of water in the bath, or rather the watt-hours for which your utility company bills you. Thus, over 24 hours, consumption at a rate of 2,000W totals 48,000 watt-hours (48 kilowatt-hours or kWh). In a year, as I’ve tried to explain rather desperately to my wife, that comes to 17,520kWh.

Twenty light bulbs doesn’t sound much, considering that it must cover all our needs, in every part of our lives: not only energy we consume at home but our individual share of infrastructure such as road-building and sewage, and the energy that goes into everything we buy. So if you want to run the oven or drive a car, you must turn off several light bulbs.

In theory, it shouldn’t be difficult, because 2,000W is what the average human uses already. But that’s an average. In practice, consumption varies enormously. The typical Bangladeshi uses just 300W. Across Europe the figure is about 5,400W. And in the US it’s a stonking 11,400W.

The Swiss have calculated that 2,000W is sustainable only as long as the whole world sticks to it. But the disparity between nations is unsustainable, they say. It’s a basic issue of fairness. That said, increasing energy use in developing countries beyond 2,000W would be catastrophic – so we must learn to use less.

The Swiss minister for the environment, transport, energy and communications, Moritz Leuenberger, concedes that the target seems, initially, unrealistic. “But the necessary technology already exists.”

Indeed, the Swiss have taken the 2,000 Watt Society into the mainstream. A large pilot scheme involving co-operation between industry, universities, research institutes and government bodies has been going for seven years in Basel. Zurich joined the project in 2005 and Geneva declared its interest in 2008.

Roland Stulz, the project’s director, insists: “It’s not about starving; it’s not about having less comfort or fun.” Indeed, he tells me one of his colleagues has already attained the 2,000W life. “It’s about a creative approach to the future.”

The three big areas of energy use are food, transport and the home, accounting for roughly a third each. On the first two I’ve made progress.

I get my food from local, seasonal suppliers (including my own allotment). I don’t eat a lot of meat, and I often eat food raw. As for transport, I have an electric car but usually cycle or take the bus. (I work at home, so don’t travel that much – just as well, because it’s hard to live the 2,000W life if you drive or fly much, or even at all.)

Home is a leaky Victorian terraced house in north London. Hoping to make savings here, I recently got my hands on several eco books. The most comprehensive is probably The Carbon-Free Home, by Stephen and Rebekah Hren, which has much to say about saving energy, including the suggestion that we install composting loos to save all the pumping and purification of water (to drinking standard) that we then simply flush away.

The typical Briton uses 160 litres a day. But rather than install a composting loo yet, I fix two interruptible flush kits from Interflush inside my cisterns. Now I can flush exactly what I need to clear the pan – a tiny bit, a bit more, or the lot.

As to the heating, I turn it off when I’m on my own. There are statistics on the internet about how much energy you save every degree you lower the thermostat. But turning the whole thing off is a lot more effective than saving the odd degree.

To get to grips with my needs, I acquired an Electrisave monitor and wandered round the house turning on lights and appliances to see how much they all used. After a day or so I felt that I had got all I needed from it. Now it was just another pointless gadget, I felt responsible for all the “embodied” energy that had gone into making it. I decided to give it away so that someone else could benefit. I had discovered by myself the 2,000 Watt Society dictum that “using, rather than owning” is the way forward.

I didn’t really need the Electrisave anyway. With a tiny bit of physics – which I missed at school – I could have conducted my own energy audit. If you know this already, forgive me: the consumption (in watts) of any given item can be calculated by multiplying the volts by the amps, and both are usually to be found on the plug. The Carbon-Free Home recommends making an inventory of every device in the house, then recording every time you turn an appliance on and off: “You may be thinking, ‘Wow, that would take too much time!’ If so, you’re probably using way too many appliances and your need for an energy diary is that much greater.”

It recommends, unsurprisingly, that nothing be left on standby. The authors don’t much approve of devices that merely amuse: “Is there ever such a thing as an efficient use of a video console, or does it always represent a failure of imagination?” Clothes should be left to dry in the sun, or at least in the air, because tumble dryers eat up to 6 kilowatts. Indeed, “Appliances that use electric resistance heat must go.”

I see what they mean. The iron uses 3,250W. The kettle uses a relatively modest 2,300W, so I decide henceforth to make tea using a Storm Kettle, designed for camping, which boils a whole litre using a few scraps of newspaper and two small sticks. Alas, this is not fast, and with the heating off I’m in constant need of hot drinks.

Then there’s my wife’s hairdryer. This uses 3,250W, like the iron. “Instead of using a hairdryer,” the book’s authors suggest, “get a less maintenance-intensive haircut, shower in the evening, or dry hair with a towel or in sunshine”.

They have obviously not met my wife, who has what she calls “bonkers” hair. If she doesn’t blow-dry it straight, it goes weirdly frizzy, which is why she does that every morning. I’ve tried suggesting that she grow it a bit longer, so that the hair’s weight pulls it into some order, but she refuses to believe it would work. I’ve refrained, for now, from suggesting that she eliminate the problem altogether by shaving it all off. Mercifully, we can make enormous savings without yet banning hairdryers. Scientists estimate that roughly two-thirds of the primary energy used today is wasted, mostly in the form of heat that nobody wants or uses. (Primary energy is the energy contained in a lump of coal, whereas “useful” energy is the light emitted by a bulb once the coal has been burnt to make steam, the steam has powered a turbine, and the resulting electricity has been transmitted over the grid.) With currently available technologies we can reduce that waste significantly, according to the man who supplies electricity to my house.

In the early 1990s, Dave Vincent was a hippie living in an old military vehicle and surviving off-grid with his own minimal energy arrangements, including a tiny windmill. It was this that gave him the idea of dropping back into the mainstream, where he set up Ecotricity, the first wind-powered electricity company in Britain. Today Vince lives in a house with all the usual fridges, freezers and so on, and he thinks it’s impractical to give them all up. Instead, we should buy the most efficient models when upgrading and put as much as possible of our domestic load into evenings and even the middle of the night.

The national grid has massive spikes in demand and must run at a big surplus; a lot of energy is also wasted by running the grid down when demand is low. Some plants come on only to meet peaks – generally the dirtiest ones. We could save a lot of energy if we flattened the peaks and troughs. “If we put a chunk of electric demand into the night-time,” says Vince, “we could save the equivalent of all the nuclear power, or about 20% of the entire grid.”

So just by setting the washing machine – or the oven when I’m baking bread – to work in the middle of the night, I can significantly reduce my share of national energy use.

But is behavioural change, which Vince prescribes, really so simple? If I tell Harriet that she has left the lights on, or left doors open, she reacts as if I have poked her in the eye.

Colin Mather, chair of North Yorkshire’s Esk Valley Community Energy Group, shares my experience of people being unwilling to change behaviour. His group was set up three years ago to promote simple things like insulation. “We did a survey of 600 homes and had a 50% response, which is extremely good. Then we targeted people and told them about grants – it’s difficult to find out what’s available. And they started to be taken up. But I still see people who say, ‘I know I should, but I haven’t got round to it yet.’ People are very hard to change.”

It might help if people knew how much they could save. This year the average domestic fuel bill reached £1,000 for the first time. By reducing consumption to 2,000W per person, households could save more than £600 a year.

The 2,000 Watt Society says that, as well as reducing consumption, it’s imperative that we move quickly towards generating three-quarters of our energy renewably. But Mather’s group, like so many around the country, is experiencing great frustration. Several sites in the Esk valley have been identified as suitable for generating hydropower, but the Environment Agency is opposed, because the river is good for salmon. “They’re not interested in energy, only fish.”

A community group nearer me is Transition Belsize, part of the nationwide Transition Town movement preparing for life after cheap oil and amid climate chaos. One of the members I meet is Alexis Rowell, a journalist turned Lib Dem eco champion on Camden council. He tells me that 890 people looked round the Camden Eco Home, a show house, in a single weekend in September – “proof that people want to see how a Victorian property can be refurbished to reduce carbon emissions and energy bills by 80%”.

I went to see the Camden Eco Home for myself. Builders had put thick insulation on the inside of exterior walls, because the house is in a conservation area and its appearance can’t be changed. I couldn’t see Harriet agreeing to that. We would have to move the ceiling mouldings and several bookcases, and lose a hefty chunk of floor space. But alas, it makes a lot more sense to do the walls, roof and floor than double glazing – about six times the energy saving at half the cost.

On my way home, I bought insulation to put round the doors and windows, and a brush to cut draughts below the front door. I’m happy to report that the effect was perceptible at once, and without any high-tech measuring device.

After that, I went to a dinner party in a part of London where everyone seems to drive a 4x4. I sat next to a woman who listened politely as I described the steps I’d taken towards the 2,000W life. She wondered if I’d hit the target. Honestly, I had no idea: the online tool for assessing this is available only in German.

Regardless, she said there was “no point”. I would be better off lobbying the UN or the government. Then she admitted that climate change and energy issues leave her feeling hopeless. “Look at India and China,” she said, meaning that they use more energy all the time.

This was demoralising. For some time people had received no replies to the e-mails they sent me, and found my phone was usually turned off. Had I lost friends for nothing? No: her point was easy enough to refute. If we do nothing, we are in real trouble, whereas we might make a difference by taking action. If your car is heading for a cliff and the prospect of falling alarms you, you don’t say there’s no point applying the brake – far less lobby the government to tell you to apply it.

Like many people, this woman was paralysed by the scale of the problem combined with the urgency. But we can’t do everything at once. And the good news is that we don’t need to. The 2,000 Watt Society points out that infrastructure needs replacing at a rate of 2% a year anyway, so we can make a great deal of change incrementally.

As for India and China, we don’t need to go round the world to find people who make our task more difficult. The person who does most to hold me up in my mission to save the world is Harriet, with her crazy hairdryer habit.

But as I looked away from my miserable, paralysed neighbour, I glimpsed my wife talking animatedly, her hair immaculately straight and shiny, and remembered that, though she may not like the idea of insulating interior walls, or sticking polythene sheets over the windows as a budget alternative to double glazing, she has put up with me talking about composting loos, turning the heating down, wagging my finger at her about leaving the lights on, and making tea out of rainwater with a pair of damp sticks.

She’s my wife, she uses far too many kilowatts, but I love her and we’re in this together. Anyway, I rather like the way she does her hair.

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