How to calculate the size of a PV System.
Sunoneness believes that the smart grid is going to make PV very attractive for businesses and residential properties.
Having the smart grid gives the utilities the opportunity to charge different rates at different times during the day.
Midday the grid’s power loads are at their highest. Solar provides the highest outputs during these times in which to offset power consumption.
Questions to think about:
How big a PV system do I need?
Are you going to use more electricity in the future?
Most likely your electrical energy consumption is going to increase. The plugin hybrid (PHEV) and all electric car (EV) are coming.
One car will typically require a 3 kw system.
How to calculate the size of PV system you need.
One person uses about  300 kwh a month.
Two people  500 kwh.
A family of 4 – 800 kwh.
The best way to determine your PV System Size is an energy bill and see how many kwh used in a month.
Your estimated yearly kwh usage would be
0 kwh
Your estimated PV System Size is
0 Kilowatts **This number is your DC Rating. Write this down for the next step in PV Watts **
Using standard multicrystalline panels with 15% conversion efficiency facing due south your PV System would require
0 square feet of roof area.
The next step is using PV Watts to calculate your system output. You will need the following information.
1) System Size  (above) DC Rating
2) Derate factor  (Sunoneness Systems are >.80) default = .77 Derate factors are all the
efficiency
losses. Inverter, wire, panels...) Derate factors
3)
Array Type  " Fixed Tilt"
4)
Array Tilt  "(Roof Slope)" Converting roof slope to degrees
5)
Array Azimuth  Which way the panels will face (due south = 180 degrees, East = 90 degrees, West = 270 degrees)
After you hit Calculate write down the yearly output for use to calculate your cost savings / payback / profits.
After PV Watts go to Cost Savings.

Use this link to calculate a PV Solar System's Output. Click on the map Colorado then click on a nearby city.
PVWatts 
Key dates are Dec 21st and June 21st (Lowest and Highest Sun Angles)
Default is set to Boulder Colorado.
Don't forget to enter the time of day. (Approx 12:00)
SUN POSITION CALCULATOR
(C)2001, Senol Gulgonul
