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One of the things you learn when you start using solar panels is there is a lot of math involved. This is particularly true when you try and figure out how many amps a 100W solar panel can generate. Because we are dealing with different units of measurements, conversion formulas are inevitable, but we will simplify it here.
A 100W solar panel can produce 8 amps per hour and up to 40 amps a day. A 12V 100W solar panel has a maximum power capacity of 18 volts but variable weather conditions can affect the final output. A 24V 100W solar panel produces 4.1 amps an hour.
How to Calculate 100W Solar Panel Amp Output
The formula is watts / volts = amps. A typical solar panel has 36 cells, each with 0.5V so that would be 17V. The same formula applies even if the voltage is different, say 24V.
While 8.3 amps is the normal / average output, in some cases you’ll see 6 or 5.5 amps. All solar panels regardless of size are rated in peak output. That is, the maximum amount of energy (measured in watts) it can produce. Because solar panels cannot perform at peak capacity all the time, the volts and amps fluctuate.
So a solar panel rated 100W such as the HK AOSD Industrial -which we like for its reliability – means it can produce up to 100 watts in peak sun, when the sun is high above the sky, hitting the cells and providing lots of power. As the day goes on the sun’s position in the sky changes, and so does solar panel production. Peak production is at its highest noontime and goes down in the afternoon.
High temperatures will cause voltage levels to drop, and this affects the amps. The hotter it is, the less power solar panels provide. It sounds strange, but even large solar panels are at their best in cool temperatures but with the sun out. Remember, solar panels convert energy, not heat, into electricity, so temperature doesn’t matter.
The voltage being drawn determines the amps produced by a 100W solar panel. The higher the voltage required, the lower the amps, the lower the voltage, the higher the amps.
100W Amps and Voltage Examples
A 100W solar panel generates 8.3 amps from 12V, but what if you connect a solar panel to a LED light bulb? These bulbs only need 2.8 to 3.5V, probably 4V as the charge gets close to completion.
Using the same formula, W / V = amps
100W / 3V = 33.3
Your 100W solar panel will produce 33.3 amps when connected to a LED light bulb. With 5 hours of sunlight a 100W solar panel can give you up to 166ah. If you want to store that power in a battery, better get one with double the capacity (360ah).
You can try this for yourself by connecting a light bulb directly to a solar panel. Make sure you do not try this with AC powered devices as they cannot be connected directly to solar panels. LED bulbs are energy efficient hence the low draw, but hook up a 100W module with a power hungry device and the results will be very different.
Important note: battery voltage determines its wattage, and it is possible for a higher capacity battery to have the same wattage as a low capacity depending on the volts.
For instance, a 90ah 12.8V battery has the same number of watts as a 360ah 3.2V battery.
90 / 12.8 = 1152
360 / 3.2 = 1152
Both have 1152 watts.
This goes to show why you must pay attention to the battery voltage because of it affects the wattage. Whether you have a 100W, 200W etc., check the battery you want to pair it with for the amp hours and voltage.
How Solar Panel Connections Affect Voltage and Amps
Solar panels connected in a series increases the voltage but keeps the amps constant. But if the connection is parallel, the voltage stays the same but the amperage increases.
If you connect 2 x 100W ROCKPALS flexible solar panels in a series, you get 24V, but the amp output remains at 8.3
If you connect the same 2 x 100W 12V solar panels in a parallel, the voltage remains at 12V but the amps go up to 17.6.
These numbers are approximations, but you get the idea of how connections affect voltage, watts and amps. No connection is better than the other, it depends on what you need. Keep this in mind you are trying to figure out how many solar panels to get 50 amps.
You can load DC devices directly to solar panels (but not AC), and if 8.3 amps isn’t enough, get another 100W module and wire them in parallel. If your load needs 24V, join the two panels in a series instead. There may be cases where combination series and parallel configurations are used.
Do Solar Panels Really Have Amps?
Amps are used by the device or appliance connected to the solar panel. There will be no amps if there is nothing drawing it from the solar panel.
What solar panels do is generate voltage depending on how many cells are on the module and the amount of sunlight available. While 36 cells is the standard, larger solar panels with 96 cells are being manufactured.
If a device is connected to the panel, we can convert watts to amps as shown above. For a 12V panel the amps will be in the 5-8 range, while for house circuits it is usually 15.
These calculations are for DC (direct current), which solar panels produce. You need an inverter to convert DC to AC, and the results will be different. inverters are not 100% efficient either so you have to include energy loses in the conversion. This is apart from the losses incurred from the panel and cables.
Solar Panel Production and Efficiency
Always assume your solar system will produce less than what you need. In other words, your system should have extra power in reserve. If you need 40 amps a day, do not presume your 100W can generate 8.3 amps per hour. It might be able to do that for 5 hours, but what if it cannot? It is better to get another 100W solar panel for extra power.
Also, buy the most efficient solar panel you can afford. A 100W solar panel with a 23% efficiency is way better than the same 100W module with 18% efficiency. This rating determines how much of the sun’s energy hitting the panel is transformed into power. If the solar panel is not converting most of the energy into electricity, the amp output will drop, so check those ratings.
Sunlight and temperature are the most important factors that determine voltage levels. Solar panels will still convert sunlight into electricity even if it isn’t hot. What’s important is the sun is high up in the horizon and hitting the cells.
Factors to Consider When Computing 100W Amps
Aide from what has been pointed out above, there are other things you need to be aware of that will influence the amps of your solar panel. The following applies not just to 100W modules but all solar panels.
- As a general guideline, 12V = 8.3 amps, 24V = 4 amps, 36V = 2.7 amps and 48V = 2 amps. The higher the voltage the lower the amps. Most solar panels are still 12V though they can reach up to 18V without load. When loaded the voltage drops.
- If you want to get the highest amps possible, use an MPPT charge controller for your battery. A PWM controller is cheaper and works fine in most cases. But there is no comparison when it comes to amp optimization as MPPT is better.
- 12V and 24V batteries are usually charged with 18 and 36V solar panels. The voltage goes down when there is load, though the drop varies. If you have a 15V load for the 18V module you get 6.3 amps. A 30V load for a 36V 100W solar panel is around 3.15 amps. The conversion is still the same, W / V = amps.
- Check your PV module specs for what battery voltage and charge controller it works best with. Most solar panels on a grid tie system are in the 30V to 60V range. Most solar arrays are configured in a series with 12 panels connected.
- 100W is smaller than the “average” solar panel for homes, which is 250W. Nevertheless it is still widely used and suitable for various applications. Most are 12V but 24V, 36V and 48v are becoming more common.
- The peak amps of a 100W solar panel are on its spec sheet. However, the number is the optimum. Because of energy losses in the cables, inverter, and the panel itself, don’t be surprised if the figure is only half of what is stated.
To summarize the main points, a 100W solar panel can generate anywhere from 6 to 8 amps on average. But the number will depend on the voltage and how it is being used. This goes to show once again that calculating solar power isn’t an exact science, but once you learn the ropes it’s easy to figure out.
I am an advocate of solar power. Through portablesolarexpert.com I want to share with all of you what I have learned and cotinue to learn about renewable energy.