It likely consumes next to no power: a proper switching MOSFET has negligible resistance when open, and has a very high gate resistance, so the photo cell does

It likely consumes next to no power: a proper switching MOSFET has negligible resistance when open, and has a very high gate resistance, so the photo cell does not have to produce any significant current. Possibly the current-limiting resistor in the power supply of the LED circuit dissipates more than the trigger circuit.