Outdoor grow box?

I have an idea to build a small grow box in my backyard. My question is "Is it worth the effort".
I have it planned out so the floor is 3'X2.5' and the walls are also 2.5' tall. I have an outlet on the side of my house so I can run an extension cord in it to powers the lights (cfl) I have. I am also getting more lights of I find out I need more. this isn't for the whole grow either, just as temporary place to raise them till they're big enough to go outside and have a better chance of survival. I'm also still getting all the supplies I need so I still have a little time before I start anything.

why don't you just make a greenhouse? It dose seem not worth it in comparison to how easy a greenhouse can be to make or even buy

You can build a small pvc hoop house for less than 100$ which imo would work better. Pvc hoop houses work great, we use them for our dep houses.

Ya build a greenhouse. You're plants will get bigger and produce more. Plus you won't run into an increase on your power bill.

Lost my internet for a while. Thanks all for the replies. My idea above was just a small box to start veging till they were about 4-6 nodes high then move them outside and start more. I ended up scrapping the idea anyway. I'm full sunlight outdoors.

This here is my big one started in March. It still has at least 4 more months of veg left.

That what I have right now all together. It a few days old now but you can can an idea. They are all seeds saved from some of the better shit I've had the last few months (too broke to buy feminized seeds or I would) the big one is female