Are you sure about the 300 Calories= 10 miles?
These are ballpark figures. It might take one person way more calories to pedal a mile than another person.
And at least it beats a car which can use over 15,000 calories per ten miles
Are you sure about beating a car? I don't know where your 15,000 calories comes from, it may very well be accurate, but keep in mind that 300 Calories of food means 300,000 calories of energy.
A food Calorie is a kilo calorie which simply means 1 food calorie is 1000 calories of heat energy.
Whether food calories is 150 times as much as the cost of electricity or 100 times or 50 times as much, either way it is WAY more expensive as a fuel source. Keep in mind, I was stating the cost of food before preparation such as cooking. That can take a lot of energy.
You might spend 0.5 kwh just to cook a meal. My bike's battery is 36v x 16 Ah which is just over 0.5 kwh, about enough to cook that meal. I could ride the bike for 30 miles with a charge of the battery or I could cook a meal with that same charge. Yikes!
The need for exercise is way over due for many Americans so your pedal generator has merit for sure. I am just saying it is not an economical source of energy in and of itself. But perhaps it is economical if you consider it may make a person healthier and live longer and feel better, and that person was willing to pay money to get that exercise otherwise, whether paying gym fees or other costs.