Electrical power for the New Horizons spacecraft and science instruments is provided by a single radioisotope thermoelectric generator, or RTG, supplied by the Department of Energy. RTGs are used on missions that cannot use solar power, yet require a proven, reliable power supply that can produce several kilowatts and operate in space for many years.
New Horizons' journey will take it more than 4 billion miles from Earth, where the Sun is just a very bright star in the dark sky. Besides taking longer than 4 hours to reach Pluto and nearby Kuiper Belt objects, light from the Sun is 1,000 times fainter there than at Earth.
Conducting missions safely is NASA's top priority. NASA informed the public about New Horizons' use of an RTG by publishing a detailed Environmental Impact Statement - or EIS - and several fact sheets. The Final EIS, which includes public comments on the Draft EIS and NASA's responses to those comments, was released in July 2005.
A description of the RTG power system on New Horizons mission and the final EIS can be found below: