Ill wind blows Npower ad into trouble

Npower, the power company, and Greenpeace have been found guilty of misleading the public over an advert for their joint initiative to sell "green" electricity.

The Advertising Standards Authority has chastised both organisations for the national newspaper ad which appeared to claim that their "green" electricity tariff, sold by Npower under the Juice brand, came from wind power.

The adverts showed a tree swaying in the wind, and implied that the power used to run a washing machine was from offshore wind. In fact, Juice electricity comes mainly from a hydro scheme in north Wales, with only a very limited proportion from small onshore – rather than offshore – windfarms.

Acting on a complaint from Oxfordshire, the ASA ruled the ad was misleading because it failed to say that, in reality, the electricity supplied to subscribers' homes came directly from the grid and was therefore from a variety of power sources, not just renewable energy projects.

The ruling is embarrassing for Greenpeace, which chose to co-operate with Npower to further its pro-renewables campaign despite Npower's troubled reputation for mis-selling. Greenpeace endorsed Juice because Npower's sister company, National Wind Power, is building a new 60-90MW offshore windfarm at North Hoyle near Anglesey, but that scheme is still a couple of years from completion.

Npower will now have to rephrase its advertisements but the ASA ruling also raises challenging questions about the way other green power suppliers, such as London Electricity, Unit[e] and Scottish and Southern, sell their products. It could also undermine attempts to champion green tariffs.

In future, all green tariff adverts will have to make clear that, technically, all the electricity will come from the grid even though their supplier has bought an equivalent amount of power from a green source. This could confuse the public.

Matthew Spencer, an energy specialist at Greenpeace, denied the ruling was a major setback for Juice. He said the ads made clear that Juice power came from both wind and water sources, but added: "We're satisfied that we're doing something pretty pioneering and successful. We're experimenting with different wordings about the way the national grid system works, but it's quite a challenging task. It doesn't challenge the integrity of the product."

An Npower spokeswoman said a genuine mistake had been made. "I don't think [the ad] was ever intended to be misleading," she said. "As soon as the ASA brought this up, we changed the picture to make it absolutely clear where our power came from."