ONLY if used instead of (or to facilitate a reduction of) AC.
For instance, if you can handle 82F with ceiling fan, but set AC to 78 without ceiling fa, then yest it's probably worth it.
It can assist with heat bills to, but to a lesser extent. It can be 'turned around' so it blows upwards, and forces the hot air near the ceiling to mix into the room.
Limitations of the ceiling fan:
- initial cost
- installation cost
- it is effective only when you are in the room. leave the room with the fan running, and might as well leave a 75W light running.
- increases heat transfer to/from walls/ceiling/floors and especially windows. Most folks don't realize this but it can be quite significant. In a still, 78F room the convection/conduction from a 100F exterior window will be lessened by the still interior air. Add a fan and it just increased the heat transfer. The energy transfer is worse in the winter as temp differentials (inside/outside) are often larger: i.e. 20F outside/65F inside = 45F differential.
- Every Single Watt the fan uses heats the house. Every single watt that goes into ANYTHING in your house ends up as heat. Fan, dishwasher, TV, doorbell, smoke detector, alarm clock. Thermodynamics, bros and sisters. A small amount of it you can carry out of the house (batteries). The rest: you pay for TWICE in the summer: once to power the gizmo, the 2nd to pull the energy back out of the house.
Have fun!