by Trystan Lea

Note: most of the linked to content on this page will redirect you to another site: EcoBro is a community group I am a member of based in North Wales, we are doing an energy auditing project at the moment called the informed energy decent project check it out here.

This is an investigation into my use of energy and an attempt to explore how I can provide that energy sustainably.

After reading Sustainable Energy without the hot air by David MacKay I wanted to do a similar analysis of my actual energy use. How does my energy use compare with the average persons energy use. How much can I reduce my energy use by and how much renewables would I need to provide that level of energy use.

I thoroughly recommend reading David MacKay's book before you read this as it gives quite a bit of context. You can read it online and for free under open source licence, follow the link above.
I found David MacKay's energy stack graphics to be the clearest way of comparing energy use and generation and his use through the book of a common unit of energy the kWh per day per person. I have tried to make use of the same methodology here.
I am very much still learning about sustainability, I have tried my best to make sure that what I have written below is accurate. I have tried to reference most statements and figures and have also added links too further reading. If you find errors or aspects that I have missed, please get in touch I would very much appreciate your feedback.

My energy breakdown

  • Individual energy use and household energy use
  • What is not included - so far my investigation here takes into account somewhare beetween a third and a half of what may be my overall energy use as it does not include my share of services or industry and imported stuff. Extending the investigation to include these things is one of the things I would like to do next.

Better heating

As I mentioned briefly in my energy breakdown: we currently get our space heating and cooking from an oil fired aga and that the problem with this (appart from it being oil fired) is that in order to cook the aga needs to be on all the time, even when you dont need so much space heating, otherwise you cant boil a kettle or fry an egg! Cooking requires about 1 kWh/d per person, when the aga is on it uses 21 kWh/d per person and so on summer days when we dont really need any space heating we are really wasting 20 kWh/d of energy.

We therefore have a great deal of potential for better, smarter heating. We need a flexible space heating system that is independent of cooking and can be turned up or down depending on room temperature.

Other possibilities


All together


This would:

  • Reduce carbon based energy use by 44 kWh/d, resulting in a 87% carbon reduction (taking into account a 2x impact of flying) of the sectors I have taken into account so far.
  • Save £650 a year in ongoing energy bills. However need to do further research to find out exactly what the payback will be as the capital costs of the mesures are substantial. Payback is likely to be in the 15 years plus range.
  • If we were to use our own wood this option could save me £870/year
  • A small decrease in heat input due to smarter, flexible heating
  • No change in miles driven.
  • A reduction in flying from one transatlantic flight every 5 years to one every 7 years resulting in C02 equivalent of 0.73 tons.

Carbon reduction of 87% in my domestic and transport based energy consumption.

Total carbon reduction of someware between 30% and 50% taking into account my share of services and energy required to make the things that I use.



I have found doing this analysis very informative. Before doing this, I felt really in the dark as to how I would be able to get to a point of sustainability.  Having a fairly straightforward and understandable framework for understanding energy thanks to David MacKay makes that goal look far more achievable, its also exciting because sustainable energy can be understood, we can ourselves work out how to get there, create our own sustainable energy plans make our own energy choices in accordance to our preferences and values.

Next steps:

  • Continue to learn...
  • Do a heating test using electic heaters with energy monitors connected and temperature sensors throughout the house to investigate the heating load required in more detail - more info on why and how to come.
  • Investigate how a wood / heatpump system combination is best designed.
  • Investigate how I can measure (roughly) my actual use of services and energy required to make the things that I use.
For now I will keep this conclusion to this. I hope what I have written above can be useful to others too and if you have any questions or have spotted errors I would be very happy to discuss any of it with you.
Thank you for reading

Trystan Lea

[email protected]