Sweden and Norway have agreed the bases for a common green certificate market, energy ministers for both nations said on Wednesday.

A green certificate is a tradable commodity proving that a certain electricity has been produced using a renewable source of energy, such as wind, solar or hydropower. Environmental groups hope they can boost the use of renewables.

The market, expected to start from January 1 2012 and to run until 2020, is seen able to generate a total of 26.4 terrawatt hours (TWh), with each country financing 13.2 TWh.

"In the period up to 2020 we will see a significant expansion of renewable energy projects in both Sweden and Norway," Norwegian Energy Minister Terje Riis-Johansen said in a statement.

Until now Sweden had its own green certificate market, while Norway had none.

Green groups welcomed the announcement.

"This is very good news," said Marius Holm, deputy leader of the Norwegian green organization Bellona.

"A system of green certificates will ensure the development of emission-free, environmentally friendly energy in an efficient manner," he said in a statement.

NUCLEAR POWER "HUGE CHALLENGE"

Separately, Swedish Energy Minister Maud Olofsson told Reuters she was confident the country's nuclear plants would be reliable this winter despite recent problems.

On Tuesday forward prices for electricity jumped 9 percent on news of troubles at two nuclear plants, Oskarshamn and Ringhals, heightening concerns of a repeat of last winter when unexpected reactor outages helped push spot prices to record-high levels.

"That is why I have been active in my dialogue with nuclear power companies to get them to deliver the power we can expect from them," Olofsson said. "Now it looks pretty good, because it is only Oskarshamn that has major concerns."

She repeated worries expressed previously by her Norwegian counterpart that the Nordic region's water reservoirs, which provide about half of the region's power supplies, have been at critically low levels for months.

"The challenge is that we have little water ... (The challenge) is also in pricing: will we come through the winter?"

Olofsson said much had been done to improve the situation at nuclear power plants since last winter.

"When power companies are doing maintenance, they must do so during a time when demand is not so great. This means that the situation is better this year than what it was last year."

reuters.com