100 watt versus 200 watt
- Thread starter vicwa20
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SolarQueen
Making renewable do-able at www.alteStore.com
Good question. It depends on what your situation is, and what the equipment is. Most 100W panels are 12V panels, designed to be the right voltage to charge a 12V battery. If you need to charge a higher voltage battery bank, just wire them in series to get a higher voltage. It can be done with a simple, inexpensive PWM charge controller. Most 200W panels and above panels have a higher voltage than a 12V panel, and therefore need a more expensive MPPT charge controller to drop the output volts down and amps up to charge the battery bank. Plus they are physically bigger and need to ship via truck if ordering online, so may end up being a more expensive solution for the same total watts.
If you have shading issues where you are installing the solar array, wiring 4 panels in parallel may be better than wiring 2 in parallel, as the output of the 1 shaded panel won't affect the others as badly as if half your panels were shaded with 2.
Then there's the downside of having more wires to deal with with 4 panels instead of 2. There's other pros and cons too, that I'm sure others will bring up. So, it's not a black and white answer of x is better than y. Like most solar design questions, the answer is usually, it depends.
If you have shading issues where you are installing the solar array, wiring 4 panels in parallel may be better than wiring 2 in parallel, as the output of the 1 shaded panel won't affect the others as badly as if half your panels were shaded with 2.
Then there's the downside of having more wires to deal with with 4 panels instead of 2. There's other pros and cons too, that I'm sure others will bring up. So, it's not a black and white answer of x is better than y. Like most solar design questions, the answer is usually, it depends.
Thanks for the information. I am looking at Rich Solar which have 12 volt panels in both 100 watt and 200 watt. The cost per watt is similar. The 200 watt is about 11" longer and 7" wider. I have limited space on top of my 25' motorhome. One or two 200 watt panels may be easier to locate the four 100 watt panels. Or, I may have to mix 100 watt and 200 watt panels depending on the space between other items on my roof. I was just wondering if I should favor one size over the other. Thanks again.
Jim Burrow
Solar Enthusiast
- Joined
- Jun 27, 2020
- Messages
- 516
With respect to my system (still on the workbench for more testing), I am limited to space on my home and need 1400 watts to supply my power needs for max house loads. However, most of the time my house load averages 500 watts throughout the day.
Because of the space limitations due to weight and shade, I have (6) 24v (rated at 39 ocv) 300-watt panels. they weigh 41 pounds each. I am using 24-volt batteries, so putting 2 panels in series will give my 2424LV MPP controller a good voltage range to regulate to run the house and charge the battery at around 28 volts.
With (3) 2 panel series, I have them in parallel where each branch puts out 7.5 amps for a total of 26 amps available to the controller. So with 60 volts and 26 amps for the controller to regulate, it has at max performance over 1500-watts to work with.
I tried other combinations of panel configuration, but with respect to voltage and current and wire sizing, the 2 series, 3 parallel worked out best for my controller. And when there is not enough power from the solar array, the battery will make up the difference, and if that still is not enough (due to low battery voltage), the Utility kicks in.
Anyway, before I actually install my system, I will check all conditions on the bench. I don't plan on installing it on the house until spring.
Because of the space limitations due to weight and shade, I have (6) 24v (rated at 39 ocv) 300-watt panels. they weigh 41 pounds each. I am using 24-volt batteries, so putting 2 panels in series will give my 2424LV MPP controller a good voltage range to regulate to run the house and charge the battery at around 28 volts.
With (3) 2 panel series, I have them in parallel where each branch puts out 7.5 amps for a total of 26 amps available to the controller. So with 60 volts and 26 amps for the controller to regulate, it has at max performance over 1500-watts to work with.
I tried other combinations of panel configuration, but with respect to voltage and current and wire sizing, the 2 series, 3 parallel worked out best for my controller. And when there is not enough power from the solar array, the battery will make up the difference, and if that still is not enough (due to low battery voltage), the Utility kicks in.
Anyway, before I actually install my system, I will check all conditions on the bench. I don't plan on installing it on the house until spring.
MichaelK
Solar Wizard
As a general rule of thumb, higher voltage grid-tie panels give you a higher W/$ ratio compared to 12V panels. 12V panels are made mostly for the automotive market where your system wiring is already 12V. If you are just charging a 12V system, with a cheap PWM controller, you can put something together producing 200-300W fairly cheaply.
Once you graduate to higher wattage systems, the break-even point seems to be around 300-400W or so. I recently helped a neighbor install a 1000W system with an inexpensive MPPT controller, and the total cost was ~370$.
A big advantage of the higher voltage systems is that you can position your panels some distance away from the batteries and transmit the high voltage power through realatively thin copper wire with less power loss. The controller then transforms the raw high voltage panel DC current down to what the 12V battery wants to be charged at.
Once you graduate to higher wattage systems, the break-even point seems to be around 300-400W or so. I recently helped a neighbor install a 1000W system with an inexpensive MPPT controller, and the total cost was ~370$.
A big advantage of the higher voltage systems is that you can position your panels some distance away from the batteries and transmit the high voltage power through realatively thin copper wire with less power loss. The controller then transforms the raw high voltage panel DC current down to what the 12V battery wants to be charged at.
