New regulations will require electricity retailers in Ontario's coming competitive market place to disclose the source of the power they sell. Starting in March, when licensed marketers may begin approaching customers, all retailers will be required to inform consumers about the province's electricity resource mix, currently 50% nuclear, 30% hydro and 20% fossil fuels. Retailers promoting environmental benefits must also provide a breakdown of their supply mix for comparison. "I think what's really important here is the mainline offerings are going to identify that they don't have any wind," says GreenGrid Electric vice-president David Argue, who will be offering a green mix including wind. "And those of us who want to move in the direction of diversification and bring on more environmentally friendly technologies have an opportunity to clearly identify how our products differ." The March implementation of the disclosure regulation is only the first phase of a two part plan to communicate details of the power supply, says Stephanie Prosen, a policy advisor with the province's energy ministry. By the late fall of 2000, when customers will actually be able to switch supplier, polluting emissions associated with each category may also be indicated. "Phase two will be the real disclosure program," says Prosen.