BETHLEHEM, Pa. -

The Christmas City is putting up green lights this year.

We're not talking about holiday lights. Bethlehem began replacing its 4,000 street lights with eco-friendly LED bulbs Monday.

Mayor John Callahan says the new bulbs are brighter and will last up to fifteen years.

"We are going to use 70-percent less energy than we had before," said Mayor John Callahan.

The mayor says this will save the city money in energy costs.

He also says Bethlehem is the first city in Pennsylvania to take on the task.