The expected value formula is

So, we have to find the probability of each event.
In this case, heads and tales have the same probability of 1/2.
Tossing no head has a probability of 1/2.
Tossing one head has a probability of 1/2.
Tossing two heads have a probability of 1/4.
Now, we multiply each event by its value, then we sum

Hence, the expected value is $2.25.