Premium Content Subscriber only Law firm Piper Alderman says it signed on more than 40,000 electricity customers to the claim over the past six months after information sessions across the state, including Mackay and Sarina. More than 1000 residents in Mackay are understood to have signed on to the claim. The firm said the claim was filed in the Federal Court of Australia on Wednesday. The class action is seeking to recover compensation for any customers who paid for electricity between January 20, 2015 and January 20 this year. The claim alleges CS Energy and Stanwell Corporation engaged in conduct that artificially increased energy pricing.