My Benchmark AHB2 consumes 0.5W at standby, 20W at idle and varying amount during use. Music power is usually very low, but it depends on type of music. The highest would be for playing sinewaves. After that probably organ or heavy classical pieces. On the other end would be a Jazz trio. Music power is very low because half of the peak loudness is 10% of peak power and in addition music has gaps. Class A is different story consuming huge amount of power all the time.
Ignoring miniscule standby or idle (because something always plays - music or TV) a listen for about 6 hrs a day = 180 hrs a month. They charge me $0.14 per kWh. Assuming 50W power draw it will make
0.05kW x 180hrs x $0.14 = $1.25 a month. If you listen loud it will be likely twice that. With your system in my room it would be about $12 a month for 5 hour a day listening, not counting idle and standby for the rest of the day. When calculating energy cost remember that they charge for energy and delivery, in my case $0.07 + $0.07 = $0.14 per kWh.
Ignoring miniscule standby or idle (because something always plays - music or TV) a listen for about 6 hrs a day = 180 hrs a month. They charge me $0.14 per kWh. Assuming 50W power draw it will make
0.05kW x 180hrs x $0.14 = $1.25 a month. If you listen loud it will be likely twice that. With your system in my room it would be about $12 a month for 5 hour a day listening, not counting idle and standby for the rest of the day. When calculating energy cost remember that they charge for energy and delivery, in my case $0.07 + $0.07 = $0.14 per kWh.