Here's the problem with pedaling a bike instead of plugging an appliance into the wall:
Let's say you pay $0.25 per kilowatt-hour and can generate 100 watts continuously while sitting on your bike inside the house. In 10 hours, you will save $0.25. Of course, you are unlikely to sit and pedal for 10 hours at one stretch, so it may take you a few days to save that $0.25.
Now, while you are sitting in the house cranking away, you're going to get pretty warm because there's not much air flow. So, you can turn on a fan to help cool you down. But the fan takes energy which eats into the output that is charging a battery, running the TeeVee, etc.
So, if your idea is to save money, then you would be better off getting a second job. It will pay a lot better and probably take less effort. If you think you're saving the environment, you might think again. There are probably more productive ways to do it then by cranking a generator by human power.
For what it does, electricity is very, very cheap.