I dialed the PSU back to 2.80A to the emitter for 5350 lumens (75% rated power). Recording an hour on my kill-o-watt meter yielded 0.07 kWh. Multiplying that by the kWh charge on my electric bill yields a cost of 0.00506 per hour to run. So an 8 hour run would cost 4 cents, or about $14.78/year @8 hrs per night.