Will an hour on a road bike be less of a workout than an hour on a heavier hybrid that has thicker tires?

As the time is the same it is totally dependent on your effort. So if you ride either bike and maintain a hart rate of 160 for example the work is identical. You will simply ride faster on a road bike.

M R is right on. is not he always?

l commute - and my commuter is a ''hybrid'' (actually just a mountain bike with slicks/street tires.

It weighs about 32 lbs.

l am a competitive person and l can not stand to be passed by ''regular'' part-time riders during the summer on their sweet road bikes.

So l think l get way more workout than they do trying to keep pace. All in fun!

See you in the bike lane.

The amount of workout depends on how much to put into it. Given the same route, distance, and time the hybrid will require more energy then the road bike.

yes, definitely. A roadbike takes about 15% less energy than a hybrid with heavier wheels and frame.