150 watts to kWh per day and month

3.60 kWh/day

for 150 W running 24/7 · 108 kWh/month · $17.82/month at 16.5¢

150 W by hours of use

Use	Per day	Per month	Cost/month
1 h/day	0.15 kWh	4.5 kWh	$0.74
2 h/day	0.30 kWh	9.0 kWh	$1.49
4 h/day	0.60 kWh	18.0 kWh	$2.97
8 h/day	1.20 kWh	36.0 kWh	$5.94
12 h/day	1.80 kWh	54.0 kWh	$8.91
24 h/day	3.60 kWh	108.0 kWh	$17.82

kWh = W × hours ÷ 1000. Devices with thermostats or compressors cycle, so actual use is often lower than the rated wattage × hours.

3.60 kWh running 24 hours, 1.20 kWh at 8 hours.