Solar Systems for Generating Electricity

PV Modules - Here are some details

There are over 300 different manufacturers of PV modules, with each manufacturer making many varieties. This makes for quite a long list of modules. And each has a specification sheet with items such as efficiency, power tolerace, Voc, Vmp, Isc, Imp, Pmax, termperature coefficient, etc. Many of these factors are needed to properly design a system that works correctly. But what factors should a buy be concerned with?
 

Cost per Watt?

What's that? Well, in the old days (last year) everyone talked about how much per watt (DC watt that is) the system cost. We won't go into much details here, since this reference does not match up with what we see on our electric bill which is kwh (kilo-watt hours). Now days you should be looking at how many kwh the system will produce over the life of the warrantly period (25 years is standard now). Then take the cost of the system divide it by the total warranty kwh and you'll get the "normalized cost per kwh". This will always be less than you pay your utlity company proving that solar is a better deal.

Where is it manufactured?

This is buyers choice. Solar modules are manufactured all around the world. Where is it manufactured might plan into the cost of the panel. Some countries have lower labor costs than others.

Efficiency a big deal?

Efficiency is related to how much of the sunlight hitting the modules surface is converted into DC electricity. You can equate this to the newest version of a gadget. The newest version costs more. The more efficient a PV module is, the higher the cost for the electicity it produces. Take for instance two 260 watt modules. Manufacturer A has an efficiency rating of 15% and manufacturer B has an efficiency rating of 18%. Each module still only produces 260 watts, but module B is smaller than module A. Module B also costs more, since it's a newer version of efficiency. So you pay more for the same amount of electricity. The only time efficiency matters is when there is not enough space to install the system.

Warranty

This is one a buyer should pay attention too. A good warranty means the manufacturer feels pretty good about their product. There are two parts to a warranty of a solar module. First is the workmanship. As of 2012, the standard warranty period is 10 years on the quality of workmanship it takes to make the module. The second is the production performance. It's called different things, but it's about how the electricity production of the panel performs over time. The latest version is a lineary quarantee of 80% at 25 years. See the warranty just below. So you can see, modules will last 4+ decades.

Power Tolerance

What is power tolerance. This is an indication of how much a module can deviate from how much wattage a module produces. It used to be that power tolerance could be -5/+10 %. That would mean you could be paying for a module that produces 5% less than the stated wattage. Not something you really want to do. Nowadays, the better manufacturers do what they call "plus sorting". The power tolerance on the specifcation sheet would say -0/+3 watts. So the module you purchase produces what you paid for and can actually produce more! The industry is getting pretty stable.

Cell Efficiency

A common mistake is thinking that the cell efficiency is a huge factor in decided on a module. The issue with that is efficiency is lost with every connection you make. So the more cells that are wired together the more efficiency is lost. How they are wired together also makes a difference. And ultimately as we stated about, efficiency is a matter of dollars not production of a system. See our Power Production Guarantee!

The Bottom Line!

Hopefully this will give you a better understanding of what matters when selecting a PV module. The main item is the warranty. Everything else doesn't matter too much provided your installer has a powerp production guarantee so you know exactly what you are buying.

Just a few solar panel manufacturers to look into: