5 watts to kWh per day and month

0.12 kWh/day

for 5 W running 24/7 · 4 kWh/month · $0.59/month at 16.5¢

5 W by hours of use

Use	Per day	Per month	Cost/month
1 h/day	0.01 kWh	0.1 kWh	$0.02
2 h/day	0.01 kWh	0.3 kWh	$0.05
4 h/day	0.02 kWh	0.6 kWh	$0.10
8 h/day	0.04 kWh	1.2 kWh	$0.20
12 h/day	0.06 kWh	1.8 kWh	$0.30
24 h/day	0.12 kWh	3.6 kWh	$0.59

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

0.12 kWh running 24 hours, 0.04 kWh at 8 hours.