Heated GH vs LED room

[lebmung]

Winter as finally gone a way, this was a long winter!

I am trying to make a energy calculation, cost efficiency simulation.

Small greenhouse let's say 3 m (9ft) by 5 m (15ft) heated during the winter or move the plants inside a building same area but with grow LEDs, heating the same temperature.

What is more cost effective?

[brian]

I think a well insulated room with efficient grow lights is probably more cost effective than heating a greenhouse in a northern zone.   If you have cheap fuel, thermal mass, and perhaps cover the greenhouse at night, the greenhouse might be cheaper. 

I definitely prefer having a greenhouse, though.  It is pleasant to be in, while grow lights are pretty harsh. 

[spaugh]

Agree with Brian except there are nice colored grow lights available.  Just need a high CRI (color rendering index) rating.

[lebmung]

The winter is cold with average temperature 3C it can go to -12 to -15C for few nights.
I want to make this comparison to see if it's efficient for 4 months to heat the greenhouse or move the plants in a room with lights then back to the greenhouse.
Light is not a problem as nobody will live in that room.

I am looking at the actual scientific calculations.
Like light wattage consumption and heat loss of the greenhouse. I have a rough idea how to make them but I have only empirical data.

[fruitnut1944]

To calculate that you'd need to know how well insulated both situations are. There are calculators online for greenhouses. Feed in the covering material, greenhouse size, temperature differential inside vs outside, and it will calculate the BTU requirement/heating cost. The grow room could be treated like a house. There surely are online calculators that would spit out the same info if you know the R values.

If the grow room is in your basement the heat from the lights would contribute to keeping the house warm. and the structure isn't an added expense. If you have to build a stand alone, highly insulated grow room it's going to be very costly.

In terms of cost the other factors far outweigh the energy bill.

[W.]

You might want to think about a system of covering the greenhouse at night, to retain the heat built up in the day. I saw a recent video on a large greenhouse in Alberta, Canada that covers the greenhouse with some type of insulating fabric at night. The video did not get into detail about what type of fabric it was or how expensive it was to put that system in place, but it did give me ideas for my greenhouse project.