A lot depends on what you intend to run in the greenhouse. Grow lights? Heaters? swamp cooler? Fans? Alarm system?

At a minimum, run 10/3UF for two 20A circuits, run as a multiwire branch circuit.

thanks for your quick response :)

I will need to have lights, fans and heaters (not necessarily going all at the same time..I have not yet figured out exactly what kind of cooling system I will put in it...or heating either.

Would this be a relatively simple job for a skilled person? time consuming? or pretty straigh forward?

I imagine the more expensive part is digging the trench for the conduit.

i would think that 2 20 A circuits would be plenty. you can use one to power either the heater or the cooling, and have the other to power the lights. more than 2 circuits will require a subpanel, so if you want to stay away from that i would go with the above suggestion.

i know here in MS we don't cool greenhouses other than with exhaust fans to suck the heat out, some have a psuh-pull setup, with a fan down low to push fresh air in, and one high to pull hot air out the top. the fans don't have to be very large either. my FIl uses a couple of Walmart Box fans, and his stays fairly comfortable.

To me the key will be the size of the greenhouse and the amount of heating needed. Once you decide on the exact electrical contents of the ghouse, then we can be more specific with recommendations.

I know a handyman who does work on the side ...

Suggest you hire him to dig the trench. Then have a licensed electrician do the wiring.

thanks to all who responded. I'll do some homework on this and when I get my specs together...I'll repost. I think the box fan idea will be sufficient, as I will really only be able to draw out the heat and circulate air. I will be checking in on the other forums (related to GHouses) and get ideas for the type of heating I'll need. What I intend to build will be approximately 8ft tall, 6 feet wide and probably 8 feet deep. It will be a pole & rafter? type stucture with an A frame roof.

Ok, that helps a lot. A small ghouse will only require 120V space heater type of heating. I'd go with normel's suggestion of 10/3 feeding 2 multiwire 20A cc'ts. That should be lots of power for that small a size of building.

Gee with the subject line I thought we were going to do the "running spark" joke.