Geepig

Well, any item on the bike will only consume energy when it changes position, and then later returns a portion of that energy. If we are riding on smooth road with no slope at a fixed speed, then the suspension will not be consuming energy, but the tires will. The tires never cease to consume energy, and if we reduce the tire pressure to the point that they can just support us then they will consume a large amount of energy - all the time. If they did not, racers would ride around on fat, low pressure tires. When the suspension deflects it absorbs energy and then returns some of it, when we ride up a hill and have to lift the component's weight, some of that energy is returned when we descend. For tires we expend energy all the time to flex them, and all that energy is lost as heat, and then as we cross bumps the tires, frame and our body still deflect and return energy like a suspension.

The only real question is whether the weight of one's chosen suspension balances out the comfort and the energy input from us, continually and occasionally.