Electricity prices are expected increase in next week's WA budget, but Premier Colin Barnett has denied reports of a 14 per cent price hike.

While the Federal Government predicts the price rise to be closer to 7 per cent, it is expected the introduction of the carbon tax could push prices up another 9 per cent.

However prices could rise by a total of 14 per cent when the carbon tax comes into effect in July.

The combined increase will cost the average household more than $200 a year, adding about $4 a week to the average household electricity bill.

The price hike comes on the back of last week's announcement of an 8.3 per cent increase in gas prices, adding about 90 cents a week to the average gas bill.