Renewable Energy Corp., a vertically-integrated solar supplier based in Norway, has put $40 million into San Luis Obispo, Calif.-based Mainstream Energy for a 20 percent stake in the company. Mainstream supplies and installs solar modules to consumers and businesses, and also negotiates supply agreements with utilities. The investment gives REC an entry-point into the US market. Mainstream itself has stakes in two smaller companies: AEE Solar, a wholesale solar distributor, and REC Solar (no relation to the Norwegian company), which handles sales and installation of systems. The agreement also gives REC the option to acquire a majority stake in Mainstream by exercising options that will remain valid for three years. [Via Reuters]