The higher the CFM the better. it really depends on how much air you need to move. There are charts online which give recommendations per the size of your bathroom.

When I researched bathroom fans for my gut-reno 3 years back Panasonic was the one to buy. You can get them through electrical suppliers as well - don't fall into the trap of buying things through bathroom/kitchen showrooms etc.

Depending upon the size of your bathroom, you might need two fans, not just one. Some people here have bathrms larger than my cottage's bedrooms!

I can heartily endorse Panasonics. We have them in both our bathrooms which have been in since 2003. Unlike the cheap Broan/Nutone original fans, Panasonics start quiet and STAY quiet, even though they work even better.

The Panasonic website has an estimator so you can match your square footage to the correct size fan. It's better to go over the requirement than under. And use a timer switch - the smaller ones are so quiet, you do forget to switch them off.

Thank you for the helpful replies. Both bathrooms are small, but we're looking for overkill.

I'd look at a remote inline blower. Panasonic has them but it's really the specialty of Fantech.

Some of their dual location ones move near 400 cfm.

Here is a link that might be useful: Remote bath fan

A typical recommendation is for 8 exchanges per hour. So for a 5x8 bath, with 8 foot ceiling, you need (5x8x8)x8 cubic feet per hour, or 42 CFM. For 8 foot ceilings, this works out to about 1 CFM for each square foot of floor space. Since you want more than typical, maybe up to double that.

I'm controlling mine with timers, so that I can have the fan run for a 10/20/30/60 minutes a shower (or other), then shut off automatically.

Here is a link that might be useful: Timer switch, just punch a time

My daughter had wonderfully quiet Braun bath fans that were over 100 cfm. They had a long squirel cage fan. I got a couple too. Not sure of the model, or how it compares to a Panasonic.

I wouldn't want quiet. I like the masking noise of a fan.

Get a bathroom fan timer. that is the best way to get maximum air exchange without having a high power fan that sounds like a jet or costs a fortune.

I am with commenter Toronto on considering inflow UNLESS you have central heat/ac bathroom, in which case air to replace the exhausted air will freely come in from the register.

If you want optimum airflow in addition to fan CFM:
a) you also should check your ducting if it is old, and make sure it has no obstructions
b) make sure your install well mating fan with your ducting.
c) get a fan timer in your switch (about $20 to $25). these can bused to insure that the fan remain on for ten or 15 minutes AFTER the users leave. It is when bather s leave, that the room has the highest relative humidity and water that needs to be evaporated and exhausted. Turning off the fan that that point is the worst thing.

My advice.
- insure you have register or window you can crack, if not have a cut made across bottom of your bathroom door.
- Get/keep moderate fan rated 6 to 8 exchanges per hour
- Get a fan timer. 15 minutes of fan after you exit is better than massive exchanges while shower is running.
- check any/all bathroom fans once a year for dust. vacuum them out. if you feel low performance maybe occurring check duct and mating of fan TO duct.

After a lot of research and talking with people who've installed them, we put the Fantech PB-270-Hs in our three bathrooms. Single fan, two grills, duct mates in a Y ahead of the fan, each grill has integrated halogen lights.

Echo what others have said - we're putting timers on ours to be able to run them for a bit after we finish in the bathrooms, to remove the last vestiges of humidity.

Here is a link that might be useful: Fantech Bath Fans