Haunted Hotel: Stay in the Light

You have just been hired at Haunted Hotel, but on your first day of work you discover that the Hotel is haunted has some quirks.
Some dark force is killing the guests staying in the dark. Using the hotel's security system your job is to protect guests and stay alive for three nights by controlling the hotel's lights.
Lights are your only weapon to save the guests and yourself. Take care the lights did not last all night, so ration the energy and good luck!

Strategy
Develop a strategy for using electricity wisely, as it will not last all night with all rooms lit.

Terror
Death is prowling the Hotel, but no one can see it. Go into each room and scan the room if death is in the scanned room it will appear. Turn on the light immediately to expel it from the room and it will return to the hallway.

Shop
At each end of the night you will earn money from the "daily rate" for every living survivor. Use this money to make improvements to your security system