Monday, 11 November 2013

Energy cost, energy use and carbon emissions

While looking through the Nedo data, I decided to look at energy use for our old house. We used electricity, gas and paraffin. The electricity came from the mains. The gas was in tanks out the back, which would be replaced every month or two, usually before they ran out. Our house was not connected to town gas, and in fact it may be more sensible in an earthquake-prone country to deliver tanks to houses rather than pipe inflammable gas around. I used to fill 18 litre tanks of paraffin at petrol stations or hardware shops, and drive or sometimes cycle them home, remembering the Russian proverb: chop your own wood and it will warm you twice.

The paraffin heated the bath water year round, and was used in fan heaters in the winter. The gas heated the shower, the stove and the geyser that supplied hot water to the kitchen sink. We also used electricity for a kotatsu table heater and an electric carpet. And we had a futon heater that blew hot air between the sheets, which we have to consider part of our heating cost.  

This is what the energy costs were. I think we were away for part of February.

By comparison, this is the energy use, converting the gas and paraffin to kilowatt hours. Although the winter use of gas, electricity and paraffin were roughly the same cost, the paraffin was packing a lot more energy. 

Here's the kg of carbon released. An 18 litre tank of paraffin will release 53 kg of CO2. This seems to be defying the conservation of mass, but what is happening is that the paraffin provides the C, while the two Os come out of the air. It's difficult to understand whether that is a lot, but over the year, as a family we emitted something like thirty times our own weight, 4.6 tonnes. It seems a lot. On a very rough and conservative estimate we're emitting about half as much carbon in the new house, which is obviously better, but still fifteen times our own body weights.

The calculation of kWh per cubic meter of gas and per litre of paraffin came from

The kilogrammes of carbon is fairly straightforward for the fossil fuels as it's chemistry, although you need to add a little bit to the amount of carbon dioxide released in burning to account for how much was used in its production and delivery. For electricity it gets a bit more complicated as you have to work out where the electricity came from. A whole new post of carbon accountancy is needed to go into this. For now I used data from, which I hope gives a roughly accurate answer.