The Rebound Effect nicely illustrated

Rebound effect

The Rebound Effect is a significant problem in energy policy and sustainable design: if new devices are more energy efficient, will users simply use them more, or leave them on for longer? (A kind of Jevons’ Paradox). This UK Energy Research Centre report (PDF, 5 Mb) looks to be a comprehensive, interesting and readable treatment of the subject.

The compact fluorescent light bulb shown above, fitted under some scaffolding over a public footpath in Hurley, on the Thames near Henley, is switched on all day, even in bright sunshine. But that’s ‘OK’ of course, because it’s one of those energy-saving bulbs.

How prevalent is this kind of thinking among users?


  1. This is yet another reason to encourage reduction of consumption the Pigouvian way: increase prices, usually with a consumption tax, to internalise the externalities.

  2. Punter: “So, these ‘energy saving’ bulbs save energy eh?”

    Sparky: “Yup. Saving energy is good for the planet.”

    Punter: “So, the more I use them, the more energy I save?”

    Sparky: “Yup. And the more money you save too.”

    Punter: “So, I should use them as much as possible, even leaving them on all the time?”

    Sparky: “Yup… er, erm, well, no.”

    Punter: “No? But if I don’t use them, I won’t save energy and help save the planet?”

    Sparky: “Actually, I think you’re meant to use these energy saving bulbs as little as possible.”

    Punter: “Oh, ok. I’ll not be buying any from you today then. Thank you. Goodbye.”

    The problem is, these aren’t energy SAVING bulbs at all. They simply consume and waste less energy than incandescent bulbs. Any saving only occurs in the comparison or substitution, not intrinsically. The laws of thermodynamics prevent light bulbs from saving energy (even solar powered ones that simply store and release it).

    They may well reduce the amount of energy mankind generates (from fossil & nuclear fuels) for its lighting, but that’s a reduction in generation, not an intrinsic saving of energy contained within the system known as planet Earth, i.e. storing it as fossil fuels, destroying it, or ejecting it into space.

    The best way of saving energy (from heating up the planet), as opposed to reducing demand for its generation, on a domestic scale would be to mirror the surface of one’s roof and reflect a fraction of the sunlight’s energy that reaches it back into space. It thus keeps the house cooler in the day, and warmer at night. However, although it saves energy in operation it isn’t particularly economic (more energy may be consumed in its manufacture and installation than in its lifetime is radiated into space over and above an unmirrored roof), especially not for the householder (unless it saves on cooling costs).

  3. NB by listing it as an option I’m not trying to suggest that it is actually possible to destroy energy (contrary to the laws of thermodynamics), just that it may be possible to remove its heating effect from the system, e.g. by converting energy into matter (not that we yet have the technology to do this efficiently 😉 ).

  4. Dan

    Thanks Crosbie and Graeme. At some point we’ll be hit by significantly higher electricity prices anyway, regardless of tax, but what difference it will actually make to user behaviour…well, I don’t know. As has come across a few times on this blog, I’m by no means a fan of some of the ways that ‘energy-saving’ CFLs have been promoted to the public, and governments.

    A friend has actually been working on a more advanced implementation of the “cooler in the day, and warmer at night” idea – “designing a roof for hot climates that gets free cooling through radiant coupling with the sky…replac[ing] the standard insulation component with an open cell honeycomb… allow[ing] longwave radiation to pass, while arresting convection”.

    Thanks to the fantastic way that most academic journals work, of course, I doubt you’ll actually be able to read the full text of that article…

  5. b

    Most likely the fluorescent was ON all day because of health and safety regulations.

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