The Premier Colin Barnett may face a party room backlash this week over a decision to cut the solar power feed-in tariff.

Last week's state budget revealed more than 75,000 people that installed solar panels before mid-2011 will now get half the money they were promised three years ago.

The figure will drop from 40 cents for every unit of power supplied to the grid to 20 cents.

The decision has prompted an angry backlash from the community and now Liberal backbencher Peter Abetz, has written to the Energy Minister Mike Nahan and the Premier's office saying the backflip is unethical.

"I think our yes should be yes and our no should be no," he said.

"I don't think we're that desperate as a government for finance that we need to break that promise."

He plans to raise the matter when the party meets on Tuesday and says if the Government values integrity, it should honour its commitment.