Greenhouses What are they?
It is possible to have a good greenhouse with no electricity. But your results will be improved and come easier if you install several systems and devices to help you.
There's the basic outlet system, of course. Some greenhouses have supplies that rival a small house. And, for good reason - they are practically that! Even ignoring commercial greenhouses that sometimes run as large as 40 feet by 60 feet or more, a homeowner's greenhouse could well be 10 feet by 20 feet.
With a structure that large, you'll have plenty of room for a variety of plants - orchids, fruits and vegetables, Bonsai (which normally live outside, but some species need protection from harsh winters) and others. With all that room, and those plants, having electrical outlets can be a big help.
Electrical outlets will make it possible to plug in space heaters, to compensate for excessively low winter temperatures when you have long days of no sun. Or, you may want to have a fan in the summer to regulate heat and supply air flow. Orchids in the wild, for example, thrive up where there are breezes. And, of course, having lights installed is essential for working in the greenhouse after dark.
Apart from these very basic systems and devices, there are many specialized tools that can make your efforts easier and safer for the plants. Automatic watering systems are a big convenience and can be adjusted to supply just the right amount of water where and when needed. High speed drills, soil heating devices and a range of even more exotic aids all require electricity.
More advanced greenhouses may have a light control system, shades or shutters, that operate by sensing the amount of light and opening or closing down automatically. That requires electricity. Solar panel systems, while neat and helpful can't always supply enough power to run larger devices.
You should plan for both 110V and 220V outlets, and enough amperage to cover the equivalent of two normal home bedrooms or more. Special-purpose outlets, conduit and other electrical components are available online or at the hardware store. If you don't have the skills to install the electrical systems, and most gardeners don't, an electrical contractor can obtain all the right parts for you.
Don't skimp on the outlets. It's annoying and unsafe to have an outlet 10 feet away when you need one at the base of your table. Be sure to order or insist on components and a supply that will more than cover your needs now and in the future. Creating an electrical system is pretty straight forward during construction. Modifying it later is difficult and costly.
Plan ahead and be prepared to devote 10-20% of your budget to the electrical system. The payoff in convenience and the health of your plants will more than compensate in the long run.