What Can I Power with a 100-Watt Solar Panel?

In this article we explore:

• How much power a 100 Watts solar panel will generate
• What size battery and charge controller you need to store the power
• Ideas of what you can power with it…and for how long.

We sell a lot of solar panels for DIY off-grid solar customers. Generally, when we design a solar power system, we start with your loads, what  you are trying to power, and from there you figure out what size solar panel you need. But now, we are going to look at it the other way around, what can you power with a 100W solar panel?

A solar panel is rated by the amount of power it creates at Standard Test Conditions. These conditions include the intensity of the sun, , the angle of the light hitting the panel directly, the temperature amongst other criterias. So the, actual mileage may vary, based on all of these factors in the real world.

We generally reduce the calculations based on the difference between the panel manufacturer setting and your actual installation. When a 12V solar panel is rated at 100W, that is an instantaneous rating, if all of the test conditions are met, when you measure the output, the voltage will be about 18V and the current will be somewhere in the 5.55 amps region.

Now that you understand the calculations behind it, we need to figure out how many hours to plug into the equation to determine how much power the solar panel system will produce in a day. How many hours of sunlight that is equal to the intensity of standard test conditions, which is basically the sun at noon, will the solar panel be exposed to during the day?

As you well know, even though the sun is up at 8 in the morning, it is not as bright as it is at noon. So you can’t just say that the sun is shining for 10 hours in most parts of Kenya, so multiply 100W x 10 hours. The hour between 8 and 9 in the morning is probably only half as strong as the sun from noon to 1 in the afternoon, so the morning hour would probably only be equal to ½ sun hour.  

Luckily, some very smart people have data for decades and calculated out the number of sun hours for all over the world, broken out by month, and even the tilt angle that the panels are mounted and by using these findings we are able to install your solar panels to exploit to full capacity the suns energy during the day.

       So what exaclty can I power with a 100W solar panel?  Well, first of all you need to store it in a battery so that you can use it later when you need it. So, using at least a 7 amp charge controller to manage putting the power into a deep cycle battery that can be charged and discharged on a regular basis. What size battery do I need? Sorry, that calls for more math. I have my 224 watt hours that I’m making, and I’m putting it in a 12 volt battery.

OK, now, I can finally figure out what I can do with that power. I can run my laptop that uses 45W for 5 hours. Because 224 Watt hours  / 45W = 4.97 hours. Or I can power 3 of my 10W LED lights for 7 hours, and still have a little power left over. Or I could make myself a cup of coffee, listen to the radio while reading a book with a 10W light on for 3 hours, and use my laptop for 2 hours.  This should give you enough information so that you can figure out how to fit this into your situation. You can change the numbers to fit your area, and your power needs.