Continuity mistake: When DeMarco lifts his glass to look at Elektra you can see there's no meniscus where the liquid hits the glass. When it cuts to a close-up of the glass there now is. (00:05:55)
Continuity mistake: In the last fight seen next to the well, the well is close behind Elektra, but when she gets hit backwards the camera cuts to a side view and the well and Electra are a lot farther apart.
Answer: Elektra's father was a wealthy shipping magnate and could afford to maintain the electric and gas bills for a house that the family hadn't visited in years.