A senate inquiry has been launched to find why so many are hit with high costs and hidden fees after switching to solar power.

“Solar owners face unfair or hidden fees on their electricity bills, also large service fees when they install their solar systems in some cases, and also exorbitant fees in rural areas for people connecting up to the grid,” said community group Solar Citizens’ national director Claire O'Rourke told the ABC.

Solar Citizens have collected 500 complaints from households nationwide, about big three power retailers AGL, Energy Australia and Origin in particular.

The inquiry has taken submissions and is now expected to hold public hearings in coming weeks. The first report to Parliament is due in March.

Over 1.3 million Australian households have installed solar panels, anticipating the investment would drastically reduce electricity bills.

Now, moves such as a cut to the rate paid to feed power back to grid mean many feel they have been slugged.

The Energy Retailers Association says customers are experiencing an adjustment phase, and it understood they were sometimes unhappy.