A good source of energy should have the following characteristics:

a) It should do a large amount of work per unit mass or volume that means it should have high calorific value.

b) It should be easily accessible and provide energy over a long period of time. Example: coal and petroleum.

c) Should be easy to store and transport.

d) Safe and convenient to use - energy sources should be safe as it is used by a large number of people and should be convenient.