Our slogan—”Same Sun. Same Equipment. Lowest Price.”—says it all: we offer low prices by cutting marketing and sales costs, and never by cutting corners with equipment quality.
Keep reading to learn more about standard measures of solar equipment quality, the equipment Project Solar uses, and what to consider when deciding between competing offers. You might also consider visiting our equipment page for a list of the equipment components we use, including data sheets.
Cell type, efficiency, wattage, and industry ratings are all important measures to consider when judging panel quality.
See below for more information on these measures, and then check out the spec sheets on our equipment page to see how our modules stack up.
Cell type: Polycrystalline vs. Monocrystalline
You might remember seeing solar panels with a blueish tint, and others that look dark black. These panels are made with different types of silicon cells, and are known respectively as polycrystalline and monocrystalline panels.
Polycrystalline: These panels have multiple silicon crystals in each cell, and appear blueish, often with silver or white backing material. They’re less efficient than monocrystalline panels, and no longer common among high-quality models.
Monocrystalline: These panels have only one silicon crystal per cell, and they have a dark black color. They are more efficient than polycrystalline models.
Project Solar uses only high-quality, black-on-black monocrystalline solar panels. This type of panel is more efficient than polycrystalline models and has a sleek, uniform appearance that adds to the aesthetic of the installations.
For more info on monocrystalline panels and how they stack up to the competition, check out this blog post: "Monocrystalline vs. Polycrystalline Panels".
Solar panel efficiency measures how much of the sunlight that hits the panel is converted into usable electricity. Higher efficiency panels produce more electricity per square foot, which can be especially valuable for those with limited roof space.
However, after around 20% efficiency, the price of small efficiency gains increases significantly. In other words, while higher efficiency panels technically perform better, we don’t believe they’re worth the extra cost beyond a certain point.
Project Solar uses only high-quality, black-on-black monocrystalline solar panels with around 20% efficiency.
Wattage is a measure of the amount of power a solar panel can produce under standard test conditions.
Be wary of sales reps who use high wattage to heavily promote a panel model. Higher wattage panels can produce more power, but since they usually have similar efficiency ratings to lower wattage models, they are often simply bigger, not better. Since you’re paying per watt, having more watts in one panel is not necessarily a benefit.
Most of the panels we use for residential installation at Project Solar are around 400W. This is on the higher-wattage side of the spectrum, but not so high that we break into the commercial range. In other words, our panels are usually the right size to maximize the space on your roof.
For more information on panel wattage, check out our blog post: https://projectsolar.com/blogs/solar/solar-panel-wattage
Various ratings exist to help determine the quality of solar panels. Two of the most important are the Bloomberg tier system (a measure of the manufacturing company’s financial health and competitiveness) and the IEC 61215 rating (a certification for weather and longevity testing).
At Project Solar, we use only panels with a Tier 1 rating and an IEC 61215 rating, meaning that your panels have been tested to withstand harsh conditions and that the company who built them is likely to be able to honor their 25-year warranty.
Beyond the solar panels yourselves, you’ll also want to ensure that you have high-quality inverters installed in your system. Some common measures of inverter quality include inverter type (string vs. micro), expandability, and failure rate.
Inverter Type (String vs. Micro)
Solar inverters come in one of two kinds: string inverters or microinverters. String inverters convert energy from multiple panels (often the whole system) at one location, while microinverters convert the energy from each panel before the panel wiring is combined.
String inverters usually have shorter warranties (around 10-15 years compared to the 25-year warranties of Enphase microinverters) and a major downside: they create a single point of failure for the system, meaning that if they go down, your system won’t work until they’re replaced.
Microinverters, on the other hand, can fail one-by-one, only affecting the panel that they are installed on and leaving the rest of the system operational. For these reasons, it’s generally accepted that microinverters are a better choice for the average home solar install.
Project Solar uses only Enphase microinverters, usually in the IQ8 range. This means that you get all the benefits of a microinverter system: no single point of failure, longer warranties, panel-by-panel efficiency, and more; all at our low prices.
Check out this article to read more about the differences between string inverters and microinverters:
What are Microinverters? How Do They Compare to String Inverters?
When choosing an inverter, you may want to consider whether it will allow you to easily expand your solar system in the future. String inverter setups can make expanding a system slightly more complex, while microinverters simplify this process.
Because Project Solar uses only Enphase microinverters, expanding your system is relatively simple. You can usually simply add more panels, each with its own inverter, instead of modifying the existing strings.
Failure rate is a metric that describes how likely an inverter is to fail within a given time period. This is an important aspect to consider when choosing an inverter, and even if a manufacturer doesn’t publish failure rates from their testing, you can often get a sense for how likely the inverter is to fail based on the warranty length.
Traditionally, string inverters come with 10-14 year warranties (12.5 years is the current length for Tesla’s inverters, for example). We can infer that the manufacturers of these inverters have budgeted for a higher number of failures after the 10th year, which is why they keep their warranties shorter. If you choose a string-inverted system, you may want to prepare to replace the inverter about halfway through the life of the panels.
Project Solar uses only Enphase microinverters with 25-year warranties. Failure rates for Enphase micros have been reported to be very low—as low as 0.05% in the first 10 years. This means that you’re relatively unlikely to have to replace a microinverter during the life of the system.
Batteries are an optional part of a solar project, but if you decide to purchase them, you’ll want to make sure you’re getting a good product. Some measures of battery quality include continuous power rating, depth of discharge, round-trip efficiency, and warranty.
Continuous Power Rating
Continuous power rating is the amount of continuous power that a battery can supply. If you want to use your batteries to power appliances that take a lot of power to run, you’ll need a battery with a high continuous power rating.
At Project Solar, we use Enphase IQ batteries, which have a relatively powerful continuous power rating of 3.84 (for a 10kWh model). You can also add a smaller 3kWh battery for another 1.28kW of continuous power.
Depth of discharge
Depth of discharge is a percentage of the total battery capacity that can be used. Most manufacturers limit depth of discharge to preserve battery life: batteries that charge and discharge fully and frequently don’t last as long.
Lower-quality batteries might have low DoD percentages, around 70-80%. Higher-quality batteries, such as Tesla Powerwalls and Enphase IQ models, have DoD ratings of 95-100%.
The Enphase IQ models that Project Solar uses have a DoD rating of 100%, meaning that all of the available capacity is ready for use.
Round-trip efficiency is the percentage of power you get back from a battery after putting power in—the percentage of power not lost by the storage process.
High-efficiency batteries allow you to use more of the energy your panels produce, while low efficiency batteries will lose more energy during storage. Lower-efficiency batteries range around 80-85%, while the highest-efficiency batteries range from 94-97%.
Project Solar uses Enphase IQ batteries with 96% round-trip efficiency enabled by their safe and efficient LFP technology.
Battery warranty is an essential factor to consider when shopping for storage options. Because most battery warranties top out at around ten years, you may need to replace your battery before you replace your panels—so, you’ll want to find one that lasts as long as possible. Warranty length also functions as a way to tell how confident a manufacturer is in the quality of their product.
Battery warranties are usually offered in both length and cycle numbers. For instance, a battery with a 10-year or 3,500-cycle warranty is guaranteed for either ten years or 3,500 charge/discharge cycles, whichever comes first.
Project Solar uses only Enphase IQ batteries with 10-year or 4,000-cycle warranties for our solar systems. This means that you could cycle your battery once every day for 10 years and still be covered by warranty.
Racking and Mounting Equipment
Racking and mounting systems have many specifications and certifications, some of which depend on the location in which they are being installed (for instance, IronRidge was the first to be awarded a Florida high-velocity hurricane zone certification). Two things you can check quickly, however, are the ISO certification and the warranty.
Industry standards, such as ISO and UL-2703 certifications, show that a company manufactures their parts to meet widely-recognized measures of quality and compatibility. Companies who have made the effort to get certified are likely to be reputable and provide good product.
Project Solar uses IronRidge and Unirac parts, both of which are ISO and UL-2703 certified (among other industry certifications).
Racking and mounting companies typically offer both “finish warranties” and “product warranties.” Finish warranties should be around five years in length and guarantee that the product won’t show noticeable wear if installed and cared for correctly. Product warranties should be twenty-five years (the same as higher-end panel warranties) and guarantee the performance of the product through that term, so that you don’t have to worry about replacing racking before the life of your panels has run its course.
Project Solar’s equipment, IronRidge and Unirac, comes with a 5-year finish and a 25-year product warranty.