As sig line suggests, I have a HX.
My machine switches itself on via a digital timer at 6.25 am every morning and gets used at 7.10 am. When Im on day shift the machine switches itself off at 8.30 am and I manually switch it back on when I get home around 6pm. It gets its end of day backflush, clean and refill at about 9.30 pm and is switched off for the night - timer set. On days I am home the machine stays on all day from 6.25am to 9.30pm.
I have had no problems whatsoever, nor have we noticed any spike in our power bill. We live rural and pay a premium for our electricity so this was monitored closely.
Personally, Ive found it takes a good 45 minutes to properly heat up my machine. At a pinch 30, but 45 is far more stable. Having invested significant money and time into my setup I simply couldnt live with the irony of serving myself, my wife or a guest something other than espresso because the machine wasnt switched on. Screw that!