The Solar Panel Business Purchasing Guide

Most solar panel business owners will need the following equipment and materials to get started:

Not included in this list is the equipment you will purchase to install for consumers, such as the solar panels, inverters, cabling, batteries, etc. The assumption is that these parts will be custom ordered for each customer after the install has been specced out by your engineers.

Here are some of the most important buying decisions that your solar panel installer business will have to make. We outline the key considerations you’ll need to keep in mind when making these purchases and provide some popular options.

Photovoltaic (PV) panels

The PV panels you purchase to install for consumers will be one of your largest expenditures. There is no single best option, so we’ll include some general considerations you should keep in mind when selecting panels. It’s important to note that you can easily purchase different panels for different customers, depending on each client’s unique situation.

Performance

The efficiency of the PV cell is probably the most-touted number in the industry, and while it’s important, it is by no means the whole story. Solar panels generally have a trade-off between price and efficiency (more efficient solar panels will generate more electricity but cost more). Most residential solar panels will hit an optimal sweet-spot of 16% - 18% efficiency. When selecting panels, compare them to this average.

Other specifications that you should take note of are the temperature coefficient and the power rating. A PV cell’s performance degrades as it’s temperature increases, and this degradation is quantified by the temperature coefficient. This number is usually negative and in units of [%/°C] to represent a certain percentage drop in performance per degree in temperature change. Smaller values (closer to zero) are better. The power rating of a panel represents how much power it can produce under ideal circumstances (higher powers are better).

Manufacturer Warranty

Solar power only makes financial sense when you treat it as a long-term investment; most residential installations pay off in around 5-10 years. While solar panels are generally very reliable (~ 0.1% lifetime failure rates), they do suffer degradation and manufacturing defects can become apparent after time. Ensure that the panels you purchase have warranties in the industry average range of 10 - 25 years.

Quality & Durability

There are several ways to mitigate quality risks and ensure you’re purchasing high quality products, namely manufacturing standards and standardized durability tests. Look for manufacturers who are ISO-9000 compliant, which means they have set up a rigorous quality control system. To ensure the panels are designed well against premature failure, look for panels that have passed the IEC’s 61215 reliability standard for silicon cells. This testing standard simulates a full product lifecycle through accelerated failure testing under extreme conditions.

DC to AC converters

PV cells produce DC current whereas a house runs on AC power, hence the need for equipment to convert DC to AC power. There are 3 types of equipment that do this: string inverters, power optimizers, and microinverters.

String Inverters

• By far the most popular option globally
• Generally the cheapest option
• Best for installations that are optimally placed and not shaded

Module Level Power Electronics (MLPE)

• Examples of these include power optimizers and microinverters
• More expensive than string inverters
• Best for installations where panels are facing different directions, or parts of the array may be shaded at times
• Generally produce slightly more power than string inverters

Each of these options can be purchased from one of the wholesale resources listed below.

The following companies are US-based wholesalers that sell all the equipment you need to install complete solar power systems. Most of these companies serve as distributors and purchase their equipment directly from the manufacturers, so you may not be getting the lowest prices. However, these distributors can offer advice and recommendations.

• Unbound Solar
• Solar Electric Supply
• Affordable Solar

The following companies are global leaders in PV cells, manufacturing and selling in bulk. Partnering with one of these companies can give you access to discount prices and some of the highest-efficiency PV cells on the residential market. Most of these manufacturers only produce the PV cells, so you’ll have to source the other equipment from different suppliers.

• Trina Solar
• JA Solar
• Hanwha Q Cells
• Suniva