Thanks for the update.

Seems like you have a 4320 watts of panels and get 3.82 power hours a day so the best you could generate is 16.5 KWH. Is the 14 KWH average available at the AC outlets or is that the just what is produced by the panels? Why do I ask? :laughing: An article in Home Power magazine said that the power loss of solar was 40% so one would only get 60% of the power generated. That 40% loss seems VERY high to me. I still am surprised that one does not get more than N number of hours of power production a day. You are getting about 4 hours a day and I would get about 5 year round. Your numbers are showing that you do get the predicted 4 hours of power production per day.

Putting money aside, the big limitation for solar is the number of hours once can produce power, the need for power out side of the few hours where power production occurs, and how much power one gets at the AC outlets. An extra couple of hours of power production really makes a difference but there ain't much one can do about. :laughing: Batteries to store power are expensive an a long term expense that does not end. When I ran some quick numbers on a limited number of batteries to allow us to run our fridge, freezer, and well, the cost for solar really jumped.

Later,

Dan

See buckeyefarmer's post #21 here:

http://www.tractorbynet.com/forums/related-topics/253320-electric-knowledge-needed-please-3.html for an explanation of what/how gets to the AC outlets in your home.

The 3.82 number you referenced as "power hours" is the annual average amount of energy, expressed in kwh, that strikes a square meter of surface area. This is the "insolation" value the pv panels convert to power--at very low efficiency rates.

The "derate" factor (top area of chart I posted) of .77, is the efficiency loss

** within** the system, beginning with the power actually produced by the pv panels. For every watt generated, .77 watts comes out the other end. I did not attempt to refine the default derate factor of .77 in my modeling--beyond my paygrade

.

The amount of power actually produced by the array varies from about 50 watts to 2900 watts during the course of a sunny day. The inverter is designed to wait for its "strike" voltage of 235 vdc coming from the pv array. When that is reached early in the morning, it loads the array down to 200 vdc and starts inverting whatever wattage is present to AC and sending it to the service panel buss bars. The inverter itself claims to have an efficiency greater than 90 percent.

The "AC Energy(kWh)" column (4447 KWH annual total) is the expected power available to use from an array rated at 4.32 kW-- as installed at my location accounting for average weather patterns and daylight hours available, and the angle the panels are mounted at (72 degrees in my case).

The number (4.32 kw) comes from having 18 panels times 240W each = 4,320 watts. It is the nominal power the panels will produce under perfect conditions in a testing lab. If the panels did that for one hour, then you would have 4,320 watt-hours or 4.32 kwh.