Many Sierra Pacific customers are starting to wonder why the power company is once again raising its rates. The average customer can expect a dollar-33 raise next June, if approved by the Public Utilities Commission. Sierra Pacific says the last time it had a rate increase was back in July. But, the power company raised its natural gas prices in October. Lake Tahoe residents, on the California side saw a rate increase on their power bill a year ago. The PUC will hold hearings on the request in the spring.