If this were a connection I was making regularly, I'm sure I'd get used to the orientation without looking, but since it will only be used during power outages, I could see this being a minor hassle each outage. It occurred to me that having the inlet box so low to the ground would create a slight hassle when plugging in the generator cord because it's too low to take a look at the downward facing inlet male plug's orientation. What is the easiest code compliant way to run wire to this inlet box? And preferably making the smallest hole possible in the wall. I don't have any experience with conduit (just romex behind walls) and the options are confusing. On the exterior wall, the box would go in the red square area. And if conduit is used, I suppose the wire should be THHN, not romex. Since this is an accessible area, I figure the wire must be in conduit. Hole in basement wall will be in the circled area. The back of the box does have a slight standoff, so it won't be flush with the wall, providing a little bit of space for a clamp to secure wire as it enters KO. I'd like to run the wire directly into the knockout on the back of the box (KO size is 3/4', but there's a reducer if I want to bring it down to 1/2'). This is the 30A non-metallic inlet I'm using. What's the easiest code compliant way to do so?

I want to run 10/3 wire from the interlock breaker in the main panel out to the inlet. One more trick I can share - most clapboards are slanted, so I cut a small shim out of the 1/2 inch PVC conduit, and placed it in the back of the box, centered on the top mounting screw-hole and screwed right thru the middle to make the inlet box sit level and plumb. And that fitting is probably the best way for you to go because it's round, not odd shaped and should fit nicely in a drilled out hole. You could do the same but your hole through the house would need to be big enough to accommodate that 1/2' fitting. They're supposed to be screwed into a PVC box with threads so I had to use a locknut ring from a normal metal clamp, and that worked fine. The clamp to the inlet box I used was one like this: So, I ran to Homer and picked up the LB (right angle) and a PVC fitting>clamp - I already had some 2', outdoor (gray) PVC so I didn't buy any but it's super cheap $2 bucks for 10 feet) - and raised the inlet box up to around 23 inches. And although I couldn't find any code on minimum height requirements, I felt the box was too low. Originally, I planned to run the romex thru the wall, directly into the inlet box.

Siemens generator inlet