About two years ago, Chicago became the largest city in the country to secure competitive electricity on behalf of its customers, reports the Chicago Tribune. This was the largest municipal supply contract in the country, covering about 750,000 households with a total of 2 million residents. According to Crain’s Chicago Business, the contract with Constellation (an Exelon subsidiary) generated significant savings for customers in 2013. Recently, however, customers have paid more than they would have under local utility Commonwealth Edison (ComEd). Mayor Rahm Emmanuel’s administration determined that going forward the contract would not generate significant savings and returning to ComEd would create more funding to support the state’s renewable portfolio standard. Therefore, the mayor opted to terminate the contract and return customers to ComEd. From May to August, customers will pay the lower of 7.145 cents per kWh or the ComEd rate, after which all customers will return to ComEd.