To cut back on use of landfills - methane gas from landfills is a major contributor to global warming - the plan would encourage recycling and charge residents for the amount of trash they throw away.
Denver may ask voters to approve higher rates for "excessive" use of electricity and natural gas. The plan also floats the idea of using insurance premiums to penalize people who drive long distances.
"You can think of them as penalties or you can think of them as market signals," said [Beth] Conover [of Greenpoint Denver]. "There's some choice involved."
One man's penalty is his government's "market signal".