No. You do not, if your electricity contract is already (spot) hourly-prized. With direct electrical heating even that is not necessary, but in order to get all the benefits of the system, we recommend you to make a spot-priced electrical contract. About half of the benefits comes with the hourly priced electricity. The second half comes by reducing temperature while you are not at home, or when you sleep.
With waterborne floor heating you do not get benefits from the system, unless you have a spot electricity contract.