Does having the fireplace on save you money?

[Drivin'tooFast]

There are systems that will produce more heat than they consume, but they are still just a heat exchanger. Some gas log systems can produce a lot of heat - BUT they also consume a lot of gas too.

Direct vent is nice because it takes in cold air from outside and uses it in a closed (glass front) system. The flame itself does produce radiant heat that can throw off thermostats.

Generally, your regular HVAC system will be much more efficient to heat the whole house than a fireplace.