Solar Power Basics

Power in Watts

Solar panels produce power from the sun, yes we got that part.  But what does power actually mean with solar output? Power is measured in Watts. As you know, light bulbs are also measured in Watts. Say a light bulb consumes 40 watts and one solar panel produces 300 watts.  300/40 = ~ 7 bulbs. A 300 watt solar panel provides power for seven 40 watt light bulbs. 

Power in Kilowatt / Hours

This part will hopefully educate you a little before the high pressure pitch you will receive from the typical solar company?  But you must understand first what a Kilowatt/Hour (kWh) means. This will help you tremendously with the jargon.

So what is a kilowatt/Hour?  It is an amount or rate of power that a power source (i.e. solar or grid) will produce in one hour. The 40 watt light bulb consumes 40 watts. But it also consumes 40 watts per hour. In ten hours, that little 40 watt light bulb will have consumed 400 watts in ten hours or 400 watt/hours (40 watts x 10 hours). When you add more electrical stuff, fridge, washer, hair dryer etc, it gets into the thousands of watts used. This is why we use Kilowatt/Hours(kWh) as a measurement. After adding up all the electrical appliances, it can go over 5,000 watt/hours!  Instead of using 5000 watts, we use 5 kilo watts. For example, 15,500 watt/hours = 15.5 kWh.

The electrical companies charge you on a kWh bases. So if you have used 400 kilo watt hours of electricity in a one month billing cycle, your will be charged for every 1kWh used. The price per kWh can vary from.10-.30 cents per kWh. 

On average, a 2000 Sq ft home consumes 30 kWh a day. So if your panel produces 10 kWh a day, then you reduced your consumption from 30 kWh per day to 20 kWh per day.

What a Solar Tracker Can and Can Not Do

The solar tracker can produce up to 40% more kWh's per day than a static, non moving, panel.   A solar tracker faces the sun directly all day. A solar tracker even adjusts to the seasons for optimum output. But a solar tracker needs room with no obstructions to work at its best. 


A Note About Roof Solar

If you place a solar panel on a roof, it's highest output will be in a 4 hour range when the sun is high up. If you have a roof with multiple small faces, you will need to add panels on all the faces to get optimum exposure. This is a good solution, but adds more panels none of which will produce at full power at the same time.  For instance, if you have three faces on the roof in East, West, and South directions but only have room for a few panels on each face, you will need to place panels on all faces.  Each set will get sun. But when the sun is directed to the East panel array, the West array will be dormant. Regardless, this may be the only choice, unfortunately it comes with great cost too.  Solar panels need to face the sun. Beyond 30 degrees trajectory, they drop in power significantly.  In low season, panel production decreases as well.