Choosing the right solar equipment is very important because the components often last for 25 years or longer. Covering modules, inverters, batteries and mounting, you will learn about the components needed for a complete solar power system.
First, determine which components you will need for the PV solar array. For grid-tied system this will include solar panels, inverter, mounting, safety switch disconnect. Inverters can be larger capacity central inverter or many smaller micro-inverters (1 for each module). Mounting can be rooftop, ground or pole. Grid-tied systems can have optional monitoring systems. For off-grid, use all of the above and add an off-grid type of inverter, a charge controller and batteries. This can often increase the total cost by 50% to as much as double.
There is no easy answer to what is the best solar panel. It can vary based on the price, performance, availability and total system design for each project. Brand A may have a great product one week, then Brand B releases a new product at a lower price the next week. We evaluate the following criteria to find the best solar panels for your home or business.
Power Ratings are the maximum and average Watts of power a solar panel should produce. The three ratings to understand are STC, PTC and NOCT. These ratings can be used to compare panels. Try to avoid a panel with high STC or factory-rating, but a low NOCT or everyday rating, relative to another panel.
STC factory-rated maximum DC watts as listed by the manufacturer, e.g. 250 watt solar panel is capable of producing maximum 250 watt continuously under ideal Standard Test Conditions. STC Peak Watts are the FACTORY rated MAXIMUM DC power generated under Standard Test Conditions for sunlight and temperature. STC irradiance at 1000 W per square meter, cell temperature at 77F (25C), air mass AM 1.5.
PTC real-world rated maximum DC watts according to PVUSA test conditions, e.g. a 250 watt STC module may produce maximum 225 watts in PTC real-world conditions. PTC Peak Watts are the REAL-WORLD rated MAXIMUM DC power generated under PVUSA Test Conditions for sunlight and temperature. PTC irradiance at 1000 W per square meter, cell temperature at 68F (20C), air mass AM 1.5.
NOCT nominal rated average DC watts according to everyday conditions, e.g. a 250 watt STC module may produce 195 watts in NOCT conditions. Nominal Watts are the AVERAGE continuous DC power generated in EVERYDAY conditions for sunlight and temperature. NOCT irradiance at 800 W per square meter, ambient temperature at 68F (20C), solar cell temperature at 113F (45C), wind speed 2 mph.
Module efficiency: Expressed as a percentage, this is the rate at which the module is capable of converting the Sun's energy to usable power. A higher % is better, but be sure to balance that with the cost of the panel. Most standard solar panels have efficiency from 14% to 20%. Some higher efficiency panels can be double the price of average efficiency panels. You may save a lot of money simply by adding one extra panel with average efficiency to achieve the same result. Also note that module efficiency is different than individual solar cell efficiency.
Brand: Also known as bankability, the brand strength reflects the financial health, market share, product reliability and service reputation of the company. This does not necessarily mean name recognition alone. Many solar brands will be names you never heard of, yet they are some of the largest producers of quality solar panels in the world.
Certification: The minimum requirement should be UL certification. This means the solar module has been independently tested for power output and durability.
Warranty: Look for at least a 10 year product warranty to cover defects and a 25 year performance or power output warranty that is backed by third-party warranty insurance coverage.
Cell technology: Monocrystalline, Polycrystalline or thin film can indicate the power output and durability of the solar panel. Mono and Poly represent about 90% of all solar panels produced. Although it is important to compare specific model to model, generally monocrystalline may generate the most power for the longest time. You may give up a small amount of performance but at much less cost with polycrystalline. Thin film modules are typically used for specialized purposes.
Price per module, affects overall budget. Solar panel prices can change often. Be careful when getting quotes for projects that are planned long into the future.
Price per watt, for both STC and PTC ratings. We also estimate the expected kilo-watt hour (kWh) production for a PV array to calculate the expected lifetime cost per kWh. This can tell you how the solar panels will compare to what you pay for utility power.
Physical Dimensions. Do you have limited space for the module or the entire array? The standard solar panels have 60 cells and generally measure 65" x 40" or 17.5 square feet. There are larger modules with 72 cells measuring 77" x 40", as well as non-standard modules with 96 or even 120 cells. Be cautious with non-standard sizes because they may be incompatible with future product generations. It all really comes down to what fits for your home at the right price and performance.
Aesthetics. Do you care how it looks? Are solar panels in visible area? Sleek, all-black look? Silver or black frame? Blue vs black appearance? Generally pay a little more for black.
Compatibility, does module have unique shape, size, frame, connector, voltage or amps that limits the compatibility with other solar panels? Solar panels with high compatibility means that you can find similar products from many different manufacturers. Don't lock yourself in to one brand or technology in case you want to upgrade or replace modules in the future.
The solar inverter converts direct current (DC) electricity from the solar panels into alternating current (AC) electricity used in the home. For grid-connected systems, the first consideration is to determine if you want a central string inverter, a string inverter with module optimizers, or a micro-inverter system. String inverters typically cost 10% to 20% less than optimizer or micro-inverter systems. They have a 15 to 20 year expected performance life. String inverter warranties usually cover 10 years, and most manufacturers offer optional extended warranties up to 20 years.
The optimizer and micro-inverter systems have a device attached to each solar panel. This means that each solar panel can operate independently of the panels around it. Optimizer and Micro-inverter systems generally cost 10% to 20% more and require extra cables and hardware, but they can produce more power, especially in shaded conditions. Studies show that with full, direct sunlight, a micro-inverter system may produce 2% to 3% more power than a string inverter system. However, with shade or other obstructions, a micro-inverter system may produce up to 20% more power.
They often have 25 year warranties and a longer performance lifetime. Optimizers and Micro-inverters are great for easy system expansion, and they work better in areas that have shading or different roof surfaces. They require a monitoring system to track performance and troubleshoot each individual module if needed.
Solar panels can be mounted on a roof-top or pole-mounted on the ground. Roof-top mounting of solar panels is the most common and least expensive option. Pole mounting is used when there is not enough south-facing roof space or there are unusual roof surfaces. If your property has a south-facing hill or sloped area, then ground mounts are worth considering.
Roof-top solar panels can be attached to most any type of pitched roof surface including composition or asphalt shingle, flat concrete tiles, curved or S-tile, slate, wood shake or metal roofs. This can include the roof on the home, garage, carport, barn or most any structure capable of bearing the weight. Solar panels can be also tilt-mounted on flat roofs using attachments or non-penetrating ballast trays for all types of flat roof surfaces.
There are a few variations of ground-mounted solar panels. The most common is a multi-pole ground mount using many concrete piers and 2" or 3" galvanized steel posts. The solar racking is attached to this substructure. There are also single-pole ground mounts that can fit as many as 16 solar panels on single 6", 8" or 10" pole. You might also consider a solar carport as a practical solution if your property allows it.
There are plenty of options when considering how to mount your solar system. We can help you decide the best and most cost-effective method for mounting solar panels for your project