Leaving electrical appliances on for hours

As I rose this morning at 5.50am, venturing into the kitchen, I hear a noise and look towards the stove.
I notice the electric hotplate is on.
I used it 14 hours ago and left it on mark 4.
Slight rise in the power bill next time.
I was surprised by my last power bill and how small it was considering I have used the heater for many hours over winter.