The Natural Philosopher wrote:
"Curiosity is about twice as long and five times as heavy as NASA's two
previous Mars rovers, Spirit and Opportunity, and its plutonium-powered
nuclear battery will provide the mobile laboratory with about 2.7 kWh
per day, far in excess of the 1 kWh per day maximum of the earlier
solar-powered rovers. The nuclear battery is also much longer-lasting
than the solar power systems used by the previous missions, and is
expected to last through the rover's planned operations and beyond,
providing the potential for the mission to be extended."

Yes but the sun is weak on Mars

Bill