1W continuous for a yeah is 8.8kWh. If your electricity is 12c/kWh that's about $1/W per year.

Well, Plantbabies, I don't have any charts or technical knowledge about kilowats and all that, but I can give you a true breakdown based on my greenhouse and conditions. Since we are in the same zone, you may be able to extrapolate it to your conditions somehow.

First, I don't know the size of your greenhouse. Mine is 1728 sq ft, and mine is a zone 11 house, which means I never let the temperature get below 55F at night. In fact its probably closer to 58F, even on those rare occasions when its 20F for a one night Arctic Blast freeze.

I have a lot more equipment in my greenhouse than you do. I have:
2-36" exhaust fans--they run from about 7:30am-6:30pm every day in spring, summer and fall to keep the temperature hopefully about 80-85, but last Sunday when it was 98F it was a struggle
one Wadsworth step controller--on continuously
4-HAF fans that run only occasionally, early am and late pm
4-additional 14" fans that run 24/7
2-pond pumps running 24/7 (one just for a spitter, one powers a small waterfall)
1-sump pump (for the cooling pads, used summer only)
1-200K BTU propane heater (has electric ignition) (used winter only)
4- floodlights (these are never used)

These were my monthly electric bills for 2004 and 2005:

2004
Jan $53
Feb $49
Mar $47
April $39
May $31
June $86
July $119
August $123
Sept $85 (we had 2 hurricanes hit in Sept and no power for over 2 weeks)
Oct $43
Nov $63
Dec $70

2005
Jan $77
Feb $76
Mar $66
April $65
May $55
June $66
July $83
Aug $94
Sept $109
Oct $87
Nov $77
Dec $83

Propane costs for heating, however, are much more variable. I get an agricultural rate for mine which is still almost $1.85/gal. I only use Propane for the greenhouse heater. Nothing else on the property uses propane.
The total cost of propane for 2004 was $2381
2005 was $1536

2005 was an EXTREMELY MILD winter and it still cost $1500 to heat the greenhouse

Bottom line is, its always gonna cost you more than you THINK its gonna cost you

I heat my greenhouse with natural gas for $90 a month @ 55F at night, daytime, I turn off the heat. This happens for 4 months. Water for 4 months is $25 a month, the other 4 months are hit and miss with little expense.

My greenhouse is 18x25 with a 9 foot ceiling.
Yours should not take much to run.

You can call your electric people and give them the info and they can tell you the average cost.

We need to throw out this totally misleading ZONE thing out the exhaust vent with respect to greenhouses. I think this is causing a lot of confusion for new potential greenhouse owners and old timers alike.

The "zones" we are in relates to what plants will survive the lowest air temperatures we will be exposed to.

What greenhouse owners need to know is in order of importance.

1. Lowest record low temperature. (That defines your heater size to keep your greenhouse above , say 34F, as your plants may not like being below 60F but they won't croak overnight.

2, The average lowest low, that is the number defines your heater size to keep your greenhouse at the desired temperature.

3. The average highest high. That defines your need to keep the intake air below the maximum your plants will tolerate.

4. Your insolation. I didn't say insulation.

Zone 8 in Florida and Zone 8 in Oregon are totally different.

However a plant that will survive a winter in florida z8 will also survive a winter in Oregon.

The point of my post? The heating cost in zone 8 Oregon will be far above those in zone 8 Florida.

The cooling cost in zone 8 Oregon will be much less than those in zone 8 Florida.

Same "zone" totally different climate.......

With all due respect, Chris in Iowa, I think that the zone thing IS important in planning how much your greenhouse will take to run, depending on how you think about it and what you grow. I have lived on both the West and East coasts and while zone 8 in the West may not be EQUIVALENT, it can be very SIMILAR at some times of the year. Its like comparing a Gala Apple to a Red Delicious, they are both apples, but just different small characteristics. Its not like comparing anyone's zone 8 to your zone 4. That would be like an apple to an orange.
I don't keep my greenhouse at a zone 11 temperature year round because I think my plants will like 60F better, I keep it that way because, yes, I do have some plants that actually just might "croak overnight" if exposed to 34 degrees, and many that would stall, quit growing and eventually die (or at least go into dormancy) if exposed to an entire winter (however short it may be HERE at 2 1/2-3 1/2 months, depending on the individual year, below about 40-45 degrees.

Having lived on the West Coast for 7 years and not being able to even get some marginally tropical plants to bloom there (which bloom freely outdoors here) due to the fact that there just isn't enough heat accumulation from Spring to Fall, yes, I agree that the climates, even though you might be the same ZONE, can be very different. Zone 10 in Southern CA HEATWISE is in no way equivalent to Zone 8 here in Florida, its much hotter here for a much more prolonged period of time. Our winter highs and lows are pretty much equivalent to the "normal" year round temps in some of So Cal (there are so many microclimates there you can't make that as a true blanket statement), but the biggest difference is that we do get occasional freezes down from Canada that So Cal USUALLY doesn't get, at least where we used to live by the ocean. But when you are talking about plants, zone does matter, no matter where you live, depending on what you choose to grow. Some plants that I grow here in a heated greenhouse in winter still need to be under protection in zone 10A in what South Floridians call a "shadehouse" in winter there, and Ihave bloomed plants indoors in my heated zone 11 greenhouse that some people in South FL 10A have not been able to bloom in their yards.

It would be way cheaper to just keep my greenhouse "above freezing" (ie make it into a zone 9B greenhouse, just having to jump up one "zone" in winter instead of 2 1/2) but it would defeat the purpose of my greenhouse, which is to grow and bloom tropical rainforest plants in a natural looking habitat year round.

I think you think of the zones in totally different terms than I do.

ok -- so what I probably really need is to find LOCAL people who have gh's much like the one I want to build.

Wonder how to do that? Maybe my AG agent can point me toward someone (if he ever gets back from wherever he's gone)

I said this before, but I'll clarify since my information is spread out in several different threads on very different topics --

our "zone" is unique. It's a very small microclimate, much like Sequim Wa. We are in the rainshadow of Mt. Hood, and get 1/10th the rain, and 10-20 degree higher temps than Hood River, just 19 miles west of us.

107 week-long runs during summer are not unusual. We've gone as high as 117 for a week. We had a 'fluke' week of 105 degrees in early June this year - very unusual that early in the year. We also had unprecedented rain throughout May and much of June. People's hot veg plants really did not start taking off until July. Most of the time we can plant early crops in the 2nd-4th week of March, but one year everyone had their gardens fully in by the 2nd week of May, and we had a hard freeze!

In winter -- we've gone (once) as low as 10 degrees for around a week. We've had 3-4 feet of snow on two occasions during the past 8 years.

Most winters we hover between 30-50 degrees, and usually only have a 'really hard freeze' once or twice a year for a short period.

:)

bihai,

I believe I do think of zones differently to you.

I think of zones as this map "This 1990 version shows in detail the lowest temperatures that can be expected each year in the United States, Canada, and Mexico. These temperatures are referred to as "average annual minimum temperatures" and are based on the lowest temperatures recorded for each of the years 1974 to 1986 in the United States and Canada and 1971 to 1984 in Mexico. The map shows 10 different zones, each of which represents an area of winter hardiness for the plants of agriculture and our natural landscape. It also introduces zone 11 to represent areas that have average annual minimum temperatures above 40 F (4.4 C) and that are therefore essentially frost free."

http://www.usna.usda.gov/Hardzone/index.html

The zone map tells you what your lowest low temperature is likley to be in your area and the map is used to determine which perennials would be expected to survive.

That is all I use the zone number for.

Calculating energy costs I use heating/cooling degree day data.

degree days make more sense than zones for heater sizing, integrals and upper bounds and all that.

Yes we do have a very different view of the zones. Mainly for me, that is because I think the USDA zone map is "somewhat" useful in a limited way if I apply it to plants that I want to landscape my yard with. Its a "loose guide" for me, no more, when landscaping. Mainly because it only deals with COLD temps. You have to use a separate criteria for HEAT here in the South. There's no one map. I think that's a shortcoming. I know a separate heat index map does exist.

But as far as the USDA zone map is concerned, I find it a lot more useful for my greenhouse. I am in zone 8B. However, I am still able to grow many plants in my yard that are supposedly only labeled for zone 9 and above. If I gardened by what books said about the zones certain plants would live in, and paid attention to the zone maps, I would be shortchanging myself on growing a lot of neato plants that actually do very well here.

I do find the concept of "zone" imminently useful inside the greenhouse though. I have plants growing and blooming in a zone 11 environment that are supposedly "zone 10 and above" plants that friends of mine in South FL zone 10 have not been able to get to bloom in their yards. I have to wonder, if I turned down the heat, would they still do as well? Probably not.

When I first moved to FL in the very early 1990's from Los Angeles, I was stunned at all that could be bloomed here, in the ground and even just in CONTAINERS in my zone 8B, that could not be bloomed in the zone 10-11 So Cal environment. Certain gingers, heliconias, vines, orchids, they will do so well here even if you have to stash them in a freeze, and they wouldn't do well in So Cal even in a "frost free" environment. I asked "Why?" many years later on a forum that was heavily weighted with West COast people, and the answer seems to be "heat accumulation". Even though So Cal where I lived was a zone 10-11 and rarely if ever actually freezes, its too cold at night most of the year, and too cool in the day most of the year, to afford the continuous heat needed by certain plants to thrive and bloom.

So when I set up my greenhouse, I had to think, "How do I want to do this?" Because actually, In FL, its much harder to cool the greenhouse in summer than it is to heat it in winter. I decided that I wanted a "conservatory style" planted greenhouse instead of a greenhouse that had benches to set stuff on, and that if I was going to go to that type of setting, I wanted it to be a jungle with everything that I could never leave out all year here. So if I was going to commit to THAT, I decided, zone ELEVEN conditions were what I wanted.

Anything that can take a zone 8B winter, even if it goes dormant and comes back as a "perennial", or gets leaf burn but survives, does not merit the zone 11 greenhouse. Only stuff that would never bloom or live in zone 8B, or is expensive of somewhat rare, gets to be in the zone 11 greenhouse.

Maybe that's a simplistic attitude on my part. I don't pay a lot of attention to how much it costs to run the greenhouse. I only keep records for tax purposes, because I do run a small mail order plant business and have to report income and expenses. If I was a huge business entity I would probably think I needed to have a more formulaic approach to the greenhouse, but I'm just not.

I admire people like you who have all that scientific stuff going for them. Its just not my focus. I'm more into just cranking up some Blue Eyed Christ, getting out the fertilizer and piddling around in my greenhouse. I don't like to think about it too much.

lol ... I probably would be more like you except that I have to provide these extreme details to get my Grant(s).

Frankly, I can't wait for all this to be over so that I can sit in my gh while it's snowing outside w/ a cup of coffee and probably cry from happiness. Just thinking about it brings tears to my eyes.

I have S.A.D., so the gh will be more than a hobby, more than a business for me.

:)
d