25 watts to kWh per day and month

0.60 kWh/day

for 25 W running 24/7 · 18 kWh/month · $2.97/month at 16.5¢

25 W by hours of use

Use	Per day	Per month	Cost/month
1 h/day	0.03 kWh	0.8 kWh	$0.12
2 h/day	0.05 kWh	1.5 kWh	$0.25
4 h/day	0.10 kWh	3.0 kWh	$0.49
8 h/day	0.20 kWh	6.0 kWh	$0.99
12 h/day	0.30 kWh	9.0 kWh	$1.49
24 h/day	0.60 kWh	18.0 kWh	$2.97

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

0.60 kWh running 24 hours, 0.20 kWh at 8 hours.