The project is part of a wider research programme at the University called Computing for the Future of the Planet.

Dubbed the Personal Energy Meter (PEM), the research team suggests the final version could be a separate device or one embedded into a mobile phone.

"The research is in its early stages and personal energy meters will never become compulsory but the growing awareness of personal responsibility to the environment combined with the popularity of social networking and willingness to share information make the idea of PEM an achievable goal," says Professor Andy Hopper who heads up the Computer Lab at the University of Cambridge.

The PEM is just one strand of current research into Computing for the Future of the Planet. Other areas include optimising digital infrastructures to reduce power consumption; developing computing techniques to make consistent and reliable predictions; harnessing more information to understand our changing environment and optimise the use of resources; and exploring the shift from physical to digital operations.

"We face considerable technical and practical challenges," said Simon Hay of Cambridge University's Computer Lab. "Our Personal Energy Meter builds on existing environmental foot-printing efforts by considering if it is possible to apportion a fair share of the energy consumed by an activity or artefact down to a personal level. We believe that it is possible to make the process virtually automatic, so that PEM users are free to go about their day normally without manually entering data."

Hay adds the increasing use of mobile phones makes it an obvious device to host the PEM that will also minimise the energy overhead of manufacturing and using the PEM itself.

The type of techniques used to estimate energy consumed on a particular journey are said to include embedded data mining, inertial sensors and GPS.