How do you make your house temperature cool during summer days and nights.?

Latley its been super hot tripple digits hot and what are some ways to cool my house without spending a fortune. We already have an ac in the living room but we dont have any in the bedrooms. Our house is the same temp as outside and at night i open the windows to allow some cool air in but the heat is trapped on the inside. We can't leave the the ac on because we have a PG&E smart meter and dont want to pay alot. Any suggestions would be great, although i don't want to put tin foil on the windows and during the day i try to keep the blinds down. sometimes its so hot i go to my car and crank the ac to high cuz the ac in the house doesnt cool the house.