USA Solar Store has been helping people offset the cost of heating water since it's beginning, and is a Renewable Energy Vermont Solar Thermal Partner.  Solar thermal can be utilized for day to day hot water use, or to assist in heating your home, in certain instances.  A solar hot water system is usually a smaller initial investment, and the simple payback varies based on the type of water heater it is offsetting.  Solar thermal collectors are typically 40% efficient, versus 15-22% efficiency for PV panels.