Generac Holdings, a leading provider of automatic, stationary standby and portable generators, filed on Tuesday with the SEC to raise up to $300 million in an initial public offering. The Waukesha, WI-based company, which was founded in 1959 and booked $628 million in sales over the last 12 months, plans to list on the NYSE under the symbol GNRC. J.P. Morgan and Goldman Sachs are the lead underwriters on the deal. No pricing terms were disclosed.