An independent power producer (IPP) or non-utility generator (NUG) is an entity that is not a public utility but owns facilities to generate electric power for sale to utilities and end users. NUGs may be privately held facilities, corporations, cooperatives such as rural solar or wind energy producers, and non-energy industrial concerns capable of feeding excess energy into the system. An independent water and power producer (IWPP) is similar to an IPP, but with a unified process to also output usable treated water.