Saving refers to something preserved.
- With the new process, we realized a saving of two hours.
Use savings when referring to banks, bank accounts, and bonds.
- We opened a savings account that yields a high interest rate.
- John won a $100 savings bond in the speech contest.
Note: One would never write, “a losses of $20”, so one should not write, “a savings of $20”.
- The girl invested her saving of $500 in a savings bond.