RESOL – Elektronische Regelungen GmbH is a German solar thermal technology company based in Hattingen. It is, according to a market survey of Sun & Wind Energy magazine (issue 2/2007), the worldwide market leader in solar thermal control technology with a market share of almost 50%. Among the products are solar thermal controllers, pump stations and a range of additional modules and accessories. 100% of the company is owned by its founder and General Manager, Mr. Rudolf Pfeil.