Energy efficiency of home phones

BT low energy power supply phoneBT announced that it was bringing out a new range of home phones with much improved energy efficiency. The claim is that ‘the new handsets boast power units designed specifically to consume around half the power of previous units’. BT said that almost all its extensive home phone range would contain the new energy-saving technology by mid-2008. Its press release gave very precise figures for the amount of CO2 saved – comparing the savings if all home phones incorporated the new technology to taking ‘57,000 cars off the road for a year’.


Conventional DECT (‘cordless’) phones consume about 2 watts when the battery is charged and 3 watts when charging. The large number in UK homes, all on 24 hours a day, means that even these low power usage figures have a measurable impact on UK emissions. Very approximately, cordless phones in the home add about half a million tonnes a year to UK emissions, or about 0.1% of the national total.

A saving of half of this would be useful. I was also interested in knowing whether the techniques used by BT to gain the claimed 50% saving could be transferred to other consumer electronics. Before making its claims about a 50% energy saving, I assumed that BT had done proper testing of existing phones and had carefully measured the energy consumption of new devices.

I was wrong. Here is the full text of an email interchange between a PR person at BT and me:


Thank you for this. (this refers to the BT newsletter announcing the new phones). Would it be possible to find out the expected electricity consumption, in use and on standby of the new range of DECT phones compared to the models you used as the base case? Apologies for the slightly nerdy question, but I am very interested to see how much electricity consumption you have been able to drive out of the devices.

Many thanks for any help

Chris Goodall


Hi Chris

I have been in contact with my colleague and have been informed that the information you require is not available at the moment. The information is currently being worked out and as soon as it becomes available we will be able to update you.

I am sorry we are unable to assist on this occasion but please do not hesitate to contact us for any other enquiry.

Regards XXXX

So BT made very precise statements to the press and to industry analysts that were simply not backed up by the facts. It made extravagant claims about efficiency gains before it had bothered to do the research to check its assertions.

If BT had made similar statements about financial matters, it would have had a legal obligation to ensure basic truthfulness. It doesn’t appear to believe it should extend this rule to boasts about its performance as a good corporate citizen.

BT’s behaviour has something of a disappointing pattern. I made similar inquiries in October last year, asking about BT’s announced plans to install wind turbines at some of its exchanges. In particular, I asked whether the company had checked to ensure that transmission capacity would be available from the local electricity distribution company. Since the sites were in remote areas with weak transmission infrastructure, this is a key question to ask. Eventually, after several rounds of correspondence, it appeared that no investigation of this issue had actually taken place.

BT uses a large amount of the UK’s electricity. Quite reasonably, it is therefore trying to position itself as a leader on climate change issues. But it is acting irresponsibly in making green claims that are not backed up by reasonable evidence.