What Questions to Ask When Buying Solar Panels

Why ask questions when buying solar panels? Can’t I simply trust the installers?  They are the experts, after all. Well, that’s not necessarily so. The good news is solar power technology is advancing rapidly. The bad news is that with new innovations from micro-inverters to solar cells made of materials derived from gallium antimonide substrates [1], technology is being surpassed very quickly.

This means that solar panel companies still have materials on hand as well as installers on staff who are familiar with systems becoming outdated and this is what they want to sell you. They may not even be familiar with upgrades from which you might benefit.

Find out if you can trust the solar installation company

It is important to find an experienced solar company that stands behind its product and workmanship and that will remain in business during the life of your solar system. 

The industry is ripe for advertising that appeals to the eco-conscious individual with buzz words to make the consumer feel that ‘we are all in this effort together to lessen our carbon footprint, slow global warming and save the planet’. 

It may well be instead that the promoter’s highest interest is really simply making a lot of money, using inferior products and unqualified workers to achieve this end.

It is up to you (the buyer) to research the company to best insure getting the value of the investment.

1. Should I use a solar broker?

Brokers often have solar power installation companies that they regularly work with, so while the language they use may even flatly declare that they are impartial to installation companies and instead are working only for you, that may not be the case.

It is not necessarily a bad thing that a broker has preferred providers. An ongoing relationship between two companies generally indicates that serious problems have not arisen on one side that might damage the reputation of the other party, but a short list of selected providers may mean that you as a consumer are missing out an on overlooked opportunity, possibly a company with a system better suited to your needs who is aligned with a different broker.

2. Where can I find legitimate customer reviews?

Many of these broker websites also contain misleading indicia that appears legitimate, like unverified or partial customer reviews.

It is important to read these websites closely, researching the ownership of the ‘brokerage’ through a separate search, researching their strategic alliances within the solar industry and scrutinizing the validity of the ratings or reviews ascribed to solar panel system installation providers.

Impartial verified reviews can be found on websites that are not selling products but instead are devoted entirely to consumer affairs and business ratings.  A consumer affairs website generally has many more reviews by customers. It will explain clearly the process and criterion for the reviews it accepts.

The business rating website will be more legal in nature, chronicling disputes and resolution rather than focusing on the quality of the product.

You can begin either by visiting one of these websites to select a short list of companies that might fit your needs or visit the website to verify the reputation of a company you are considering.

It is a good idea too, to ask a prospective installer for references and follow up by calling these customers with a list of questions in hand, beginning with how long they have had their system so that you have a timeline to compare customer experiences.

Learn about all the costs of installing a solar system

The list of questions you ask the references should include:  Were there any costs that were not included in your initial quote or that you were not anticipating?

1. What costs can I expect?

Overall, the average cost of installing a 5 kilowatt system in the United States presently is around $15,700 before the 30 percent federal tax credit and any other rebates [2].

Understand that this is just an average and will vary from state to state as well as with particular rooftop configurations. Too, your needs may be greater than a 5 kilowatt system.

What does this include?

First, the cost of the solar panels themselves.

What do solar panels cost?

The upfront cost will vary with the quality of the panels selected. Read Why Are Solar so Expensive for a discussion of the different types of panels available. 

Remember that the more expensive panels are typically more efficient and will save you more money over time due to the increased power production. 

For a comparison of panels presently available, visit What Are the Most Efficient Solar Panels on the Market.

In conjunction with the quality, you must consider the number of solar panels you need and can fit in the allocated space.

2. What other hardware do I need in addition to the solar panels?

Inverters are necessary to transform the electricity produced in the solar cell from a direct current to the alternating current electricity used in American household systems.

A central inverter or string inverter covers the entire solar array whereas micro-inverters are on the back of each panel. Micro-inverters were invented to solve the problem of the entire array performing at a subpar level when only one or a few panels are affected by shade, debris or snow. 

A third option freshly on the market is the power optimizer [3], designed to “optimize” the direct current produced by a solar panel before feeding it into a companion inverter converting the DC current into AC.

While this product manufactured by Tesla has a 30-year warranty and may well be a viable option in this situation, it has not been on the market long enough to prove its projected cost savings, and you may still be looking at a traditional solar panel system. 

With a traditional solar panel array, you will also need the system to affix the panels onto your roof if that is where you are placing it. Panels can be placed on tile, composition or metal roofs and brackets and hooks are available to affix them. Alternatively, you may choose to mount your solar array on a ground rack.

Three different options of mounting systems are currently available. They can be fixed, that is placed in a permanent position which is fine where continuous sunlight during daylight hours is available. 

If you live far from the equator, the sun arches differently seasonally and an adjustable system with a rotating bearing to adjust the tilt of the panels will take advantage of the changing arc.

Finally, tracking systems are available where the panels move to “track” the progress of the sun across the sky, maximizing available sunlight. A tracking system will require site preparation including burying wires and grading [5].

3. Do I need a battery?

Solar power is generated when the sun is shining. Accordingly, excess energy can be either stored on your premises for use when the sun is not shining or, if the option is available in your area, you can feed the extra energy into the electrical grid feeding your residence or business and draw upon it during the “off” hours.

If you choose to store your own energy, several different manufacturers offer solar batteries for this purpose. These will probably be made of either lead acid, lithium ion or saltwater.

Specifications differ widely, so you will need to evaluate a number of factors besides just the battery’s storage capacity. The capacity is measured in kilowatt hours of electricity the battery can store.

However, that is not a measure of how many kilowatts it can provide at a certain moment in time. 

The latter is measured as a “power rating” and can best be understood as follows:

• A battery with high power rating and a low capacity could sustain the energy need of your entire home, but only for a short while.
• A battery with a low power rating and a high capacity could run fewer appliances, but for a long time.

Another consideration is the battery’s depth of discharge, referred to as DoD. Generally, if you run a battery dry, it will not recharge or will recharge fewer times in its lifetime, so it is best to run it low, but not dry.

The depth of discharge is the percentage you can drain the battery before recharging it for optimal battery life. For example, if you have a 10 kilowatt hour battery and its depth of discharge is 90 percent, you can use 9 kilowatt hours before recharging it. 

Finally, you need to consider what is known as the battery’s “round-trip efficiency.”  A battery is not 100 percent efficient in storing energy fed into it. For example, if you feed ten kilowatt hours of electricity into the battery and get nine kilowatt hours available to draw, the round-trip efficiency is 90 percent.

You will also want to compare the warranties covering battery life. Most home energy systems “cycle”, or charge and drain, daily. A battery’s ability to hold a charge diminishes over time. If a battery has a warranty for ten years or 5,000 cycles at 75 percent, this means that at the end of the warranty period, the battery will have lost no more than 25 percent of its ability to store energy.

As with any other hardware and as discussed above in selecting an installer, you will want to research the product and its manufacturer’s reputation and track record.

You can buy more than one battery and for space considerations, may want to look at stackable batteries.

The Tesla Powerwall has received a lot of publicity as well. It is a flat battery that can be mounted directly on an interior wall. It is an attractive option and becoming more readily available to consumers [6], but do remember to consider mounting hardware and installation costs in addition to the retail price of the Powerwall.

4. What are the soft costs?

Well, for starters, they are definitely not soft!

As discussed in  Why Are Solar Panels so Expensive soft costs, that is the cost of labor for installation, costs involved in obtaining permits, and requisite electrical, structural and fire safety inspections, as well as connection costs can comprise 40 percent of the cost of the system. 

And on top of these permitting and installation costs, don’t forget to add a rider to your homeowners’ insurance policy to cover the system.

5. What is involved in permitting?

While several advocacy groups are pushing for legislation to equalize and streamline the permitting process and costs to encourage growth of solar energy across the United States, permitting remains a challenge in many jurisdictions. 

The State of California requires all of its city and county governments to have an expedited, streamlined process for residential rooftop solar systems smaller that 10 kilowatts and to provide a simple checklist for the permit process [7]. But they are far ahead of most jurisdictions. 

As an example, that may even include a requirement for a grading pre-inspection for a ground mount system. A structural safety inspection may not only require proof that the roof can sustain the weight of the panels, but in some jurisdictions the integrity of the system in high winds or through seismic activity must be certified. 

Permitting costs include not only the application fee, but also paying qualified independent contractors to certify compliance to electrical and fire regulations.

In many jurisdictions, local officials will have to be scheduled for government inspections and these sometimes require fees on top of the permit application fee. Scheduling all of these inspections can be maddeningly time-consuming as well.

6. What is involved in connecting to the grid?

The solar panel installer should have a licensed electrical contractor familiar with the local utility interconnection requirements to connect your system to the local electric grid. The cost can vary depending upon the utility’s metering requirements. If your array is on the ground and a distance away, you may have the additional expense of burying a utility line.

While the electrician will confirm the installation requirements with the local utility and ensure compliance, you will be entering into a separate contract with the local utility concerning the power you are feeding into the grid. Accordingly, you should contact them directly to discuss the interconnection contract terms. 

Questions about maintenance and warranties

1. How do you know how well your system is performing?

Most solar monitoring systems gauge, display and record the energy being produced by your system in real time. But how do you know if it is operating optimally?

The most sophisticated monitoring systems measure your production against a database of forecasted production for your area. The database was compiled in partnership with the Department of Energy [9].

A typical monitoring display screen will show how much energy your system is producing and how much you are using at the moment, and can show the daily summary as well as historical production and consumption data. It will also show the state of charge of your battery.

Many monitoring systems record and store this information so that the user can go also go online and access data in real time or past data. 

Say, for example, you are not home, but want to check your system’s performance in December, you can find that, compare it with the forecasted output and determine if you have a problem. Or if you are concerned that perhaps you have a crack in a panel or your inverter is not working properly, you can compare your output against projected output in real time.

2. What problems can arise to adversely affect performance?

The most common equipment failure is with the inverter.  

Inverters will probably not last the lifetime of your system, so you can expect to replace our inverters at least once.

An inverter typically comes with a five to ten-year warranty. This is important to look for as it is estimated that inverter failures account for 50 percent of major system failures [10].

When considering any hardware replacement warranty, it is important to understand whether the cost of labor to remove and install the defective equipment is covered.

If you are replacing hardware components such as an inverter, look to trusted manufacturers and at a minimum, confirm that the component has a UL number which indicates that it has been tested and listed by Underwriters Laboratories, which is probably the most reputable not-for-profit electrical testing laboratory in the world [11].

Again, because this is the inverter is the component most likely to fail, it is important to purchase it from a reputable manufacturer who has been in the business long enough to understand its life span and will stay in business long enough to honor its warranty.

The same principles apply to tracking systems which will have more moveable parts than a rooftop array. Read the warranty carefully to ensure that it covers hardware replacement and service installation and repair costs.

3. What about solar panel warranties?

While solar panels are very durable, built to withstand temperature changes, heavy snows and hailstorms, solar panel manufacturers do offer warranties guaranteeing support and coverage in such event. It will also be worthwhile to explore what your homeowners’ insurance rider covers.

Most system installers offer a limited period warranty for faulty installation.

Other degradation issues such as soldering lifting at the joints, moisture ingress, delamination and hotspots may not appear for years and will probably not be covered under a panel warranty, but only under the general power output warranty, discussed below.

A hotspot is where a weak cell in a string cracks due to overheating from a string of good cells dissipating all of its generating capacity into the compromised cell [12].

A more general warranty, frequently offered but more difficult sometimes for the owner to prove is the power output warranty. This warranty which is often for the expected lifetime of the system, for example 25 years, it guarantees that system performance measured in peak power output, won’t fall below a specified lever, say 85 percent over the term of the warranty. 

In this scenario, it is worth considering that a panel or two may not be performing at all, but the entire system is still producing at 85 percent. Some companies offer a secondary warranty for purchase, guaranteeing a higher power output for the initial years.

Panels typically come with a limited period workmanship warranty covering defective panel parts

Small cracks appearing in the solar cells from temperature changes and weather conditions generally degrade the system over time. They cannot be repaired; the entire module must be replaced. Their effect on the output will determine whether it is worth it. 

When you are purchasing your system, discuss this possibility with the seller and get a written repair quote for a panel and installation of same, just so you have an idea what this may cost if it is not covered and you feel it would be worth it to replace a cracked and degraded panel.

It may not be a simple matter to determine the cause of the decrease in power output as it may be from a component not easy to isolate like a faulty electrical cable. It might be worth your time to watch the installation to better understand the architecture of your system and to discuss diagnostic techniques with the installer for the more common possibilities.

4. What maintenance is required?

For snow removal, read our article at How Well Do Solar Panels Work in the Winter.

Apart from snow removal, if your panels are not at an angle where it can slide off, then the only maintenance required on a rooftop system is keeping the panels clean of debris, dust or smearing from smog. If you are leasing your system, routine maintenance is the company’s responsibility.

If it is your responsibility, ask your installer for a reputable local company you can call to periodically clean your panels or to remove the snow if you do not want to use a solar snow rake.

Is all of this worth it?

This summary is intended to help you understand solar power system purchase options so that you are better educated when shopping. 

It is recognized across the globe that generation of power through a photovoltaic system is clean, reliable and environment friendly [14]. It is time to move away from fossil fuels and the commensurate drastic harm to our planet, measured ecologically and politically.

And it is now affordable, paying for itself in utility bill savings over a short period.