A 2016 study done by Kansas State University, commissioned by the American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE), a radiant heat system can operate at 25% more efficiently than a forced-air heating system.
This is because in-floor heating minimized the heat loss in the heating system itself. All the heat leaving the system is heating your home and not leaking to the outside through ductwork. Which means that the in-floor heating system doesn't have to make up for the loss of the heat.
Another way in-floor heating is more efficient is of its even distribution. The whole house gets evenly heated instead of having the warm spot near the heating vent and the cold spots across from it. That means you don’t have to run the warm spot warmer to make up for the cold spots, because the cold spots just don’t occur, so you can be more comfortable at a lower temperature setting.
Another nice thing about having radiant hot water pipes in your concrete is that the concrete holds the heat, creating a reservoir of heat for colder nights or when you lose power.
And the nicest things of all: your feet are happy, even when you forget your slippers!