Greenpeace has drawn up a "red list" of power supply companies it says consumers should ditch in favour of environmentally friendly providers and is offering prizes to those who do.

The "clean energy" website was aimed at getting ordinary consumers to think about where their energy came from and what impact their supplier might be having on climate change, said campaigner Vanessa Atkinson.

"Burning fossil fuels like coal, oil and gas to generate electricity contributes to climate change, the greatest threat we face.

"Using renewable energy does not produce greenhouse gas pollution."

The website lists the country's nine major electricity companies and ranks them from red through to orange and green with green being the cleanest.

Meridian Energy is the only company in the "green" band, ranked as the "cleanest energy company" because it uses only renewable energy sources and was committed to using renewables such as wind and solar power in future, she said.

Trustpower is next because it uses only renewable energy sources but is marked down because "it has not ruled out using fossil fuels in future".

Top of the baddies list is Mercury Energy, owned by Mighty River Power. It gets the highest red rating courtesy of its plan to refire the mothballed Marsden B power station near Marsden Pt by burning coal.

Next on the baddie list is Genesis Energy, which owns Huntly power station. Greenpeace says the station is the only coal-fired one in the country and "belches out millions of tonnes of carbon dioxide every year with mercury, arsenic and dioxin", all thought to contribute to global warming.

But company spokesman Richard Gordon said trying to convince consumers to switch electricity suppliers because of concerns over climate change was fairly pointless.

Also, all electricity generated in New Zealand was put on the national grid so it was impossible to tell where it came from, he said.

The Huntly station was also the vital supplier of electricity to most of the upper North Island, including Auckland.

"It's Greenpeace's call but we are not ashamed of the fact we are a CO2 emitter, the station is vital to New Zealand's economy.

"There is really not very much we can do about it in the short term."

The site allows consumers to select the area where they live and tells them which "cleaner energy" supplier is available.

Everyone who switches a supplier ranked as being better for the climate goes into a draw to win a solar water heater, mountain bike or solar energy charger.

Green list

Meridian Energy is ranked by Greenpeace as the "cleanest energy company" because of its commitment to renewable resources.

Trustpower is ranked second because it uses only renewable energy sources but is marked down because it has not ruled out using fossil fuels in future