Donnachadh McCarthy: The Home Ecologist

Grab a pen, jot down your electricity usage, and watch your emissions plummet

Yes! I finally did it. My home has become "climate positive". On 24 June last year, I wrote down my electricity, gas and water meter readings, and the latest read-out from my electricity export meter. The latter measures the electricity produced by my solar electric panels but not used by the house, and so exported to the national grid. I send EDF Energy an annual bill for the total exported.

I first achieved a net surplus on my electricity usage a few years ago, meaning that on average I've been exporting more electricity to the national grid than I've been buying. However, due to the gas used for heating and cooking, my house remained a net contributor to the climate crisis. Having installed a wood-burning stove last October, I hoped this might be the year in which I'd achieve my dream.

To calculate the carbon emissions of your gas and electricity usage, take the total number of kilowatt hours used over the year from your bills or meter readings. Then, using the simple CO2 calculator on the National Energy Foundation website, convert those kilowatt hours into kilograms of CO2. Divide by a thousand to get the number of tonnes of CO2 emitted.

The figures initially looked good, but after my calculations I determined that I had missed my zero target by a paltry 0.03 tonnes. I was gutted. So near and yet what seemed so far.

But then I realised that I had calculated my imported electricity as though it were generated by fossil fuels, when in actual fact I buy from Good Energy, which only generates its electricity from renewables. When I re-calculated, I let off a whoop: the figures showed that the house had reduced the amount of CO2 in the atmosphere by 141kg. In other words, I had not only achieved climate neutrality but actually had to invent a new term: the climate-positive house. I think mine may be one of the first retro-eco homes in London to qualify.

The average amount of CO2 emissions for a household in the UK is six tonnes. The total per UK citizen, including transport and flights, is about 10 tonnes; the international average is 3.5 tonnes. We all need to get to below one tonne as soon as possible, if the dreadful flooding scenes seen recently across the north of England are not to become a regular global nightmare.

The Stern report into the economics of climate change said that we have less than 10 years to take urgent action, or else face the climate crisis running out of control. While I invite you to join me in a celebratory glass of organic cider, I also ask you to do one thing today. Go and write down the readings from all your utility meters this second. Put them in a place where you will easily find them in a year's time. Circle the date on next year's calendar (which, before you ask, you'll find at the back of this year's diary). You can then share my excitement as your carbon emissions plummet. We really need every home to be climate positive as soon as possible. Are you up for the challenge?

Donnachadh McCarthy is an eco-auditor and author of 'Saving the Planet Without Costing the Earth'

d.mccarthy@independent.co.uk