It will take a lengthy amount of searching -- one or two days of active hunting around the kitchen, if you're wholly focused on the kitchen, and using your know-how about how these types of systems work -- before Hank and Connor would find the electricity store! It is located in the kitchen area, behind a locked door and bolted door, which will take some doing to open. It seems to be a manual lock, rather than an electrical one, so it can be pried open with brute force or by picking the lock itself. It would take another day of focus on the door to get it to open. How you do that is entirely up to you, but it's a huge pain in the ass.

However, doing so would certainly give them access to the only real source of electricity that they've found thusfar. It's seems to be a fairly powerful battery of some type that is wholly dedicated to running the kitchen, but seems to a self-running technology of some sort. Nuclear fission? Who knows. It works, that's all you know.