# Watts in Solar Panels

How does the amount of watts affect a solar array?

The solar array I found is 14 W, so what would I encounter if I purchased an lower/higher wattage? I'm going to purchase an array to charge my electronics on a trip I will be taking soon and I think I understand how volts/amps affects charging, but watts are still a bit hazy. If a device needs x amps and y volts, it uses xy watts, correct? Does this mean that a 14 W solar array could charge a device using xy watts and another one that uses 14-xy watts?

• Solar panels are usually rated in W(p), that is the power it can deliver under ideal circumstances. Practical circumstances != Ideal circumstances. Rule of thumb for e.g. Netherland, averaged over a whole year, you have to derate a solar panel to about 10% of its W(p) rating. Of course the number will improve if you only take couple hours during sunshine into accout. This rule of thumb varies per location BTW. See also: electronics.stackexchange.com/questions/36273/… Commented Jun 29, 2014 at 10:41

Your understanding of Watts is correct. Power = Voltage * Current. Power is measured in watts, so your "xy" analogy is accurate.

One thing that you should keep in mind is losses that occur between energy conversions. Even if a device is rated at Z watts, it may sometimes draw more than Z (or sometimes less than Z). Try to have a little extra margin on your solar array output wattage and you will be fine. Happy Travels!

• What difference would a solar array with a higher/lower wattage make? Less/more possible devices plugged in? Commented Jun 28, 2014 at 21:03
• @RonaldSnew Correct. Each device you plug in draws a finite amount of Watts. This information can be found on the device's power brick. If you have a cellphone charger that outputs 5V 2A, thats a 10W power draw. If you plug in two of those chargers, you will have a 20W power draw. The wattage that is written on the power brick is almost always the upper limit of the Power draw (on average, they will draw less than 20W together). Commented Jun 28, 2014 at 21:07

Don't forget that, although the higher wattage does theoretically mean you can charge more gizmos, you don't get to choose the voltage or amperage. The voltage and amperage are both essentially fixed by the nature of the solar panel. You will need a dc-dc converter or something like that to convert the voltage of the panel to what your gizmo needs to charge. Unless the panel has something attached to it that converts it's own voltage down to the 5volts that most phones etc. charge with.