The radical move was decided on Friday by the Social Democrats and Greens which command a majority of seats in the town council.
It takes the 79,000-head town way in front of most other areas in the country – anyone who fails to fit a solar panel on their roof when building or altering their house, could be fined €1,000.
Generally such rules are only applied to new buildings, but in Marburg, the only opt-out will be if a building is being fuelled by other renewable energy.
A share of the costs will be met by state money, while heating bills will be but once the solar panels are installed and working.
“It's all well and good when you tighten up the rules for new buildings. But the most energy is used in older buildings,” Marburg Mayor Franz Kahle told the Associated Press.
The German government is committed to trying to meet 14 percent of all energy needs with renewables by 2020.