People who make an effort to be eco-friendly - for instance by recycling glass bottles, turning off lights and unplugging cellphone chargers - have no idea what they're on about, according to a new survey. Those who don't bother are more likely to know what actually saves energy and what doesn't.

This revelation comes in a new report from the Earth Institute at Columbia Uni in the US, analysing responses made by Americans in 34 states.

The respondents in the survey showed lamentable ignorance of which actions taken by a normal consumer actually have any serious effect on how much energy he or she uses - and thus, probably, the amount of carbon emissions he or she is responsible for.

For instance, one highly popular activity among green-conscious folk both in the States and the UK is the recycling of glass bottles. The respondents in the survey actually considered that glass bottles require less energy to make than an aluminium can, which is totally wrong. Glass requires so much energy to make - or recycle - that it is always more eco-friendly to use aluminium cans, even if one is talking about virgin cans compared to recycled bottles.

As a true eco-person, you shouldn't be recycling glass: you ought not to be using it at all.

Again, when asked what the single most effective thing they could do to save energy, the most popular response in the survey was to turn off lights. In fact lighting accounts for a relatively small proportion of the average person's energy use and almost all of us could save far more juice (and carbon) in other ways - for instance by turning the heating down as little as a single degree, something which many extremely keen lightswitch nazis refuse to do.

Another behaviour which people commonly consider to be energy-virtuous is the unplugging (or switching off at the wall) of appliances on standby or unused cell-phone chargers. This is an even bigger waste of time than switching off lights: a modern TV on standby uses less than a watt of power. You would need to unplug it or switch it off for a year to save as much energy as it takes to have one-and-a-half baths.

The list goes on. According to the researchers:

For example, participants estimated that line-drying clothes saves more energy than changing the washer’s settings (the reverse is true) ... So long as people lack easy access to accurate information about relative effectiveness, they may continue to believe they are doing their part to reduce energy use when they engage in low-effort, low-impact actions instead of focusing on changes that would make a bigger difference.

Perhaps the killer revelation from the survey is that it is, in fact, the very people who are keenest and most active about reducing their energy consumption who are the most ignorant.

Participants who engaged more in energy-conserving behaviors had less accurate perceptions of energy use and savings, possibly reflecting unrealistic optimism about the effectiveness of their personal energy-saving strategies compared with alternative ones ...

In other words, ignore that earnest friend of yours who recycles religiously, turns off their lights all the time and unplugs the telly every night. (This person may also have a rooftop windmill and/or a gas CHP unit.) They quite literally have no idea what they're talking about.

And ignore the many worthy public organisations - for instance the Energy Saving Trust here in the UK, which you pay for through your taxes - which have made us all so ignorant.

The full report, Public Perceptions of Energy Consumption and Savings, can be read in pdf here. ®