How to Determine Volts, Amps, and Watts of a Solar Panel

How to determine wattage, volts, and amps from a solar panel

When building a solar panel or looking for a solar panel, you should always know the final wattage, volts, and amps that you want the solar panel to produce. Your solar panel should always use the same size and same type of solar cells as well to keep the power consistant. Larger cells produce more current, or AMPS, and smaller cells produce less current. This is why it is important to make sure that you have solar panels that are similar in wattage, amps, and voltage output - and here is how you do it!

Difficulty:

Easy

Instructions

Things You'll Need

• Solar panels
• solar cells (optional)
• voltage meter
• sticker on solar panel that tells you amps, volts, watts

1. When determining the overall wattage of a solar panel we use this simple equation:

   Watts equals Volts multiplied by Amps

   This equation can be used to find volts, amperage, and wattage if you know any two of the three variables.

2. Why do we use this equation? Solar panels are rated on three measures of power - Watts, volts, and amps. The first thing you need to know about solar cells (the blue things that make up a solar panel) is that typically all of them creates a little more than .5 volts of DC electricty - no matter what physcial dimension they are. The only thing that changes with the size of a solar cell is their current, or AMPS.

3. SOLAR CELL EXAMPLE:

   Lets take a commercially available solar cell with the dimensions of 3 inches by 6 inches. A 3 x 6 solar cell's electricity output is more than likely rated at .5 volts with 3 amps. If we were to break that solar cell into two equal halves, we would get two solar cells that rate at .5 volts and 1.5 amps each. So volts stay the same, but amps changes with solar cell size.

4. So now that we have an idea how individual solar cells are rated and how their power production is rated - how do we know how many solar cells to use to make a final solar panel with a pre-determined amount of wattage? Or how do we know how to connect up solar panels that we bought commercially to achieve a higher wattage? We do this by using the equation for wattage:

   Watts equals Volts multiplied by Amps

   So lets say that we want to create a solar panel that puts out 60 Watts. We know that our 3 x 6 solar cells put out .5 volts and have 3.3 amps. So we take 60 watts divided by 3.3 to get our overall solar panel voltage.

   60watts divided by 3.3 amps equals 18 volts.

   Now that we have our overall solar panel voltage, we can find out just how many solar cells we need to get 18 volts out of the solar panel. To do this we take:

   Solar Panel Voltage divided by single solar cell voltage equals the Number of cells needed per panel

   So in our example, we found out that a 60 watt solar panel will have 18 volts. So now we take 18 volts divided by .5 volts it equals 32 solar cells needed. So we know now that it will take us 32 .5 volt solar cells to create a single 60 watt, 18 volt solar panel. This means that we will need to wire these solar cells together in a series to achieve the voltage increase we need.

   If you bought any solar panels commercially, lets say you bought three 60 watt panels, all you have to do is make sure that each panel has the same voltage and amperage. Then connect them in series to achieve a solar panel array (grouping of panels) that puts out 180 watts - but keeps a consistant amperage and voltage level.

5. FYI: Most commercial solar panel systems consist of individual solar panels being connected in a series to produce higher watts at a steady amperage. For example, a 180 watt, 3.6 amp solar panel system may consist of three 60 watt, 3.6 amp solar panels connected together in a series. The overall productivity - 180 watts - of the solar panel system depends on all three of the 60 watt panels working efficiently. And if you wanted to connect up a bunch of solar panels to increase your wattage - you would need to make sure that they all have the same amperage and voltage. You achieve higher voltage by connecting solar panels in a series together.

Tips & Warnings

• You do not want to mix different sized solar cells together when you ar building your own solar panel because the current or AMPS of your solar panel will be limited by the smallest cell in the group - wasting the power of the larger cells. This is important also if you buy panels and try to connect them together - make sure they have the same amperage and voltage.

• ONLY USE SOLAR CELLS OF THE SAME SIZE AND SIMILAR AMPS WHEN BUILDING OR GROUPING TOGETHER SOLAR PANELS.

Resources

• My Solar Projects Blog