AMITYVILLE - An Amityville man just became Long Island Power Authority's 5,000th customer to install solar panels. Bill Ketcham says he made the switch to cut down his monthly power bill. He says he's saving about $150 per month, which figures out to about 60 percent.After federal and state tax savings, and a large LIPA rebate, Ketcham says the system cost about $9,800. Industry experts estimate he'll make that money back in just a few years thanks to his power bill savings.