The best source of electricity is laptop batteries, which is a common item found on desks, shelves, and the trash/recycling. You can also automatically get electricity from solar panels, although this is a very slow process.
|20 + 10 (x0-1)||Laptop battery|
|5 + 3 (x0-1)||Battery|
|2||Busted microwave oven|
|2 (x0-1)||Phone battery|
- Engine-generator set - 30