As we dig deeper into the solar system design process, things can get complicated. For one, choosing a solar panel comes with a lot of considerations of value, efficiency, and power. With so many solar panel manufacturers out there, how could anyone possibly sort through all of the numbers to find the best panel for their needs?
Fear not, most solid solar contractors can navigate you through the module choice easily, as they are constantly evaluating the quality and value of modules on the market.
Your solar company probably has relationships with different suppliers, working hard to get the best prices possible for their clients. This means that the panels preferred by one solar installation company may be different than another’s, and that preference might shift every few years.
Without delving into the intricacies of photovoltaic function and exact cost-per-watt, here are a few components of solar panels that serve as guides for what you may need for your installation.
Though a lot of solar systems are similar, every system must be designed for a specific building. For this reason, you'll want to make sure your solar contractor has an engineer who reviews and approves designs in terms of the more technical aspects of the install.
Each roof’s pitch, insolation (sun exposure versus shading), orientation, size, and available space contribute to the output of the system. Each of these factors adjust the potential kWh output.
A slightly pitched roof (20-degree pitch) and a steep roof (45-degree pitch) will both produce slightly less energy than a 25 or 30-degree pitch. A common misconception is that a flat roof is optimal, but the lack of an angle means that the panels do not receive as much direct light from the sun’s path throughout the day, unless they are mounted to ballasts.
Shading effects can also make a big difference, and vary based on the shade-producer (for example, trees or neighboring buildings). They will also vary with both the time of year and time of day, which determine the angle of the sun.
The orientation, or azimuth, of the roof plays a big part in its productivity, as this determines which way your panel array will face all day and how much light it will receive.
Many think western roof faces are best, assuming that the strength of the heat from the west is what helps produce energy. While you can get a lot of production from a western-facing array, and those panels will add another layer of insulation from that heat, it is actually southern-facing roof spaces that get the highest production numbers from systems in the South. In fact, you can achieve decent production on any roof face, as long as it doesn’t have a northern azimuth!
The amount of usable space on your roof ultimately dictates the system size you can install. A very small roof or a largely shaded roof may not be cost-effective. Luckily, there are super efficient panels that are intended for use in small space situations (see the Efficiency section).
On the other hand, you might have tons of space and be able to take advantage of less costly materials, like thin-film solar panels. For example, Stion panels, made here in the Gulf South, are not the most efficient panels, but they are made entirely in the U.S. and are affordable enough to create large, well-priced systems for those with a lot of roof space. They are also all-black, and many clients love their uniform look.
Most solar panels are about 14-15% efficient. This is a good percentage, and works well for the majority of buildings. It's worthwhile to note that these numbers describe module efficiency, not cell efficiency. While many cells make up a module, be sure to evaluate the efficiency of the whole module.
Nowadays, when people want an ultra-efficient lightbulb, they buy LEDs. When you want an ultra-efficient panel, you buy SunPower panels. SunPower panels contain patented technology and are by far the most efficient modules on the market.
Efficiency really means getting the greatest power for the smallest footprint, so if you don’t have a large unshaded space on your roof, SunPower might be the best choice for you. These panels are also a favorite of mega-investor Warren Buffett. Check out his solar projects if you have any doubts about solar’s economic viability.
A system cannot be judged by the number of panels it contains. In the industry, we talk in kilowatts. There’s a big difference between a 25-panel system and a 25-kilowatt system!
Just as 60-Watt lightbulbs are not as powerful as 100-Watt lightbulbs, you are not going to get as much power per panel with lower wattage panels. A kilowatt (kW) rating is the starting point from which your system’s possible output can be determined.
From the size of the system in kW, the more accessible kilowatt-hour (kWh) projection follows. Think of kW as the amount of energy that could be produced at any moment, and kWh as the total amount of kW that is produced over time. A module that produces 1 kW steadily over 1 hour has produced 1 kWh of electricity.
You pay for electricity in kWh, not kW, and your system will produce enough kWh to significantly reduce what's drawn from the grid. A quality solar company will be able to get a very accurate read from your roof as to how many kWh your system will produce each year.
The total wattage of your system, along with roof conditions and the efficiency rating of the module, will determine the actual output of your system. Until a solar consultant and engineer have looked at your roof specifically, no one can tell you exactly what you can expect to save from going solar!
When it comes to top-tier panels, you can expect thorough quality checks and standard-to-excellent warranties. It’s also a good idea to look at their foundations. Just as you would look at your local solar contractor’s background and future plans, you should also consider the panel manufacturer’s place in the industry.
I love to design systems using Q Cells panels. They are the most popular panel in Europe, and our installers report that they are hardy and reliable in the field. Q Cells got picked up by Hanwha in 2012 and kept most of their staff and production facilities, not to mention our clients.
Rather than warranties being backed by a small manufacturer, they are backed by a multi-billion dollar conglomerate that is diversified across many different sectors. Hanwha is in a great position to back up any warranty claim for years to come.
There are certain brands of solar panels that some people prefer aesthetically, either because they blend in with a certain roofing material or because they look extra-sleek on their own. These modules may not be the most efficient or the most affordable, but that doesn’t mean they aren't viable choices.
Fortunately, there are enough high-quality solar panel options in the market that you can create a solar system perfectly suited to your needs. But make sure you communicate your priorities to your solar account manager, so they can create the optimal system for you.
Post by Sam Fleming