Key Questions to Ask When Ordering Residential Solar System

If you’ve done the research and decided that solar power is right for your home, it’s time to reach out to one of the best solar companies near you. They’ll do a survey of your home and any obstructions in the area around it, then give you an estimate that will show how many solar panels you need, how much they’ll cost, and how soon they’ll pay for themselves.

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At this point, you’ll likely have a lot of questions, and you may not even know all the right ones to ask. That’s where we come in.

There are five main categories of questions to ask:

• Questions about the company

• Questions about solar equipment

• Questions about money

• Questions about the work being done

• Questions about the future

You have to ask these questions to get a clear picture about how the installer runs their business, the quality of materials they use, the cost, performance, and expected payback time of the installation, and finally, how the work will be completed and what will happen if you ever have a problem.

If the solar company you’re interviewing can answer them to your satisfaction, you can rest assured that you’ve done the right thing — and get ready to soak in the sun!

Get quotes for your own home solar system

Information the installer should give you in a quote 

A good solar quote should contain enough information to make you feel confident that the installer knows what they’re doing and will provide you with all the information necessary to make a decision. It should answer more questions than it raises.

We always recommend getting quotes from more than one solar contractor so you can compare what each one offers. It’s also a good way to see which one takes winning your business more seriously. 

Here’s a detailed list of all the information you should expect to see in a solar quote:

Solar quote must-haves

• Solar panel make/model, and number of panels to be installed

• Total system size in kilowatts (kW)

• A satellite photo or 3-D representation of your roof showing proposed panel layout

• Inverter or microinverter model

• Expected electricity production in kilowatt-hours (kWh) per year

• Anticipated savings in dollars per year (with a clear number for estimated annual increase in utility rates)

• Information about any solar incentives for which you qualify

• Total system cost before and after incentives, broken down by dollars per watt

• Solar loan upfront/monthly cost and the price if you pay cash

• Information about warranties on equipment and workmanship

Bonus info

• Multiple options for panels/inverters at different price points

• Comparison of solar costs vs. estimated utility costs over time

• Details about the cost to add a home solar battery

• Information about a solar production monitoring app, such as those offered by Enphase, SolarEdge, etc.

As we said above, a good solar quote should answer the most important questions, like how much the solar panels cost and how much you’ll save. By reading the quote, you should then know all the essential information to determine whether the proposed solar installation will be a good financial investment. Here’s a video that shows how to evaluate a solar quote:

Once you’ve examined the quote thoroughly, it’s time to learn a little more about the company themselves and the process going forward.

Questions about the installer 

Unless you’re choosing your sister-in-law’s new solar company because she’s trying to gain some experience, you should pick an installer with a good deal of experience under their belt. You should also make sure they’re licensed to work in your area, and insured against liability for mistakes and accidents. 

Finally, solar installers in the United States have the option of becoming certified by the North American Board of Certified Energy Practitioners (NABCEP). We strongly recommend choosing an installer who will ensure a NABCEP-certified professional will be on site at all times during the installation. 

Here are the questions you should ask a solar installer about themselves:

• How long have you been in business?

• How many solar systems have you installed?

• Are you NABCEP-certified, licensed, bonded and insured?

• What is your business license number?

• Can you share references of at least three satisfied customers?

• How much experience do you have working with my local utility company?

• Do you subcontract work on your systems, and if so, how do you ensure your subcontractors do a good job?

Satisfactory answers to these questions should put you at ease that the solar company is well-established and staffed by professionals. The last two questions in particular are important.

Local utility companies all have different rules about how home solar energy systems will connect with their grid, and installers with experience know how to make sure things are done right to ensure that process goes smoothly. 

Subcontractors aren’t a bad thing; in fact, many solar energy companies use subcontracted roofers to attach solar racking systems and master electricians to do final connection of the system to the electrical panel. Still, it’s good to get clarity on it, because top installers will be clear and forthcoming on this point. 

If you use the solar calculator on SolarReviews to find installers near you, you can rest assured that you’ll be matched with certified pros with experience in the solar industry. Our site also has review pages for every installer with information on their certifications and verified reviews from real customers. 

Estimate system size and calculate solar panel costs and savings

Questions about solar equipment 

When it comes to solar equipment, most installers use high-quality brands with good warranty coverage and longevity, but it always pays to double check. 

You should be 100% sure that what you’re putting on your roof for the better part of the next three decades is built to last and compares favorably to other products on the market. Luckily, SolarReviews offers real customer reviews of solar panels, inverters, batteries, and more. 

That doesn’t mean you shouldn’t ask the installer about the equipment they choose. You should! 

Here are the questions to ask about solar panels and other equipment:

• Why did you choose the equipment you did?

• What kind of system do you have on your own roof or business?

• What warranty protection is available for the solar panels, inverter, etc?

• What problems have other homeowners had with their solar equipment, if any?

• Who do I contact if something goes wrong with my equipment?

• How much would it cost to add a solar battery?

• Do my solar panels need protection from animals?

Warranties

One of the best ways to compare brands is by reviewing the solar panel warranties they offer. Warranties should at minimum provide 25 years of coverage for power production and 10 years of coverage for workmanship.

Several manufacturers—like Sunpower, LG, and Panasonic—provide 25-year warranties for both on their top panel models. 

Inverters

Solar string inverters generally have a warranty of 10 years (but some offer add-on protection for additional years), meaning they’ll need to be replaced at least once during the time you own them. 

Microinverters from companies like Enpahse are warrantied to last 25 years, just like the panels. They can fail from time to time, meaning you might lose power from a single panel while you wait for the replacement.

Batteries

It’s likely that you’ll never need to have a home solar battery; power outages are generally short, so the only thing you’ll lose is the temporary comfort and convenience of all the electrical appliances in your home. 

However, recent problems in California and Texas have shown that blackouts can be deadly, and the peace of mind that comes from a solar battery can be worth the cost, even if you never need to use it.

Adding batteries to a solar system at the time of installation comes with some specific advantages. When batteries are designed as part of the system, you generally have your choice between DC or AC-coupled. The difference isn’t huge, but it’s worth exploring. 

Some of the installation labor cost might also be reduced, meaning a battery that’s installed concurrently with solar panels may be a bit cheaper than a battery added later. You can see this when you look at Tesla's website when you look at Powerwall costs when the battery is ordered on its own versus when it's ordered with Tesla solar panels.

Further, if you wait to install a battery, you’ll almost certainly be offered the AC-coupled variety (such as the Tesla Powerwall) that stores electricity only after it’s been converted from DC to AC by your solar inverter. That isn’t necessarily a bad thing, but it does lead to a small amount of additional power loss due to the conversion.

Animals

Pay special attention to this question. Most places in the USA don’t see significant problems from animals messing with solar panel installations, but it’s possible that the squirrels in your neighborhood are extra ornery and like to build nests underneath solar installations or chew exposed wires. 

There are products on the market that fight these problems, and your installer will be able to tell you whether other customers have had trouble with animals. 

Questions about money 

The biggest consideration for most homeowners is cost, and closely tied with that is savings. As we said above, a good solar installer should provide a quote with the total cost, estimated savings per year, and payback period. 

The quote should also include information on the incentives available to you, especially the federal solar investment tax credit (ITC), which can earn you 26% of the cost to install solar panels back as a tax credit the year after installation is complete.

Here are the questions to ask about costs and savings associated with your installation:

• How can I be sure I am eligible for the solar tax credit?

• Are there other incentives, and how do they reduce or repay the cost of the system?

• When are payments for the system due? Is the entire amount due at one time?

• How long will it take for the solar panels to pay back their cost?

• What rate of increase in utility costs do you use in your estimates?

• What financing options are available?

• Will the payments for financed solar panels increase over time?

• Will solar panels increase my home value?

Solar tax credit 

It is a sad truth that not all solar salespeople are straight shooters when it comes to your eligibility for solar incentives. You can only claim the 26% solar tax credit if you owe at least that amount in taxes. 

Put another way, you have to have income. Some retired people have been told they qualify for the tax credit by unscrupulous salespeople even though they don’t have income. Your installer might not be a tax pro, but they should be straight with you about what it takes to qualify for this incentive.

Other incentives like solar rebates or SRECs don’t require income to claim, and your installer should be the expert in helping you get qualified and claim those incentives.

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Savings estimates 

Another place where some salespeople don’t tell the whole truth is in solar savings estimates. These calculations rely on information about how much electricity your solar panels will make each year, the average annual increase in the cost of that electricity on your energy bills, and whether your state offers net metering. 

Your installer should be able to give you a straight answer about the calculations they used to determine solar production for your rooftop. Installers may use one of the many expensive software programs that can do these calculations, but you can use the free PVWatts tool from the National Renewable Energy Laboratory to get a ballpark idea of whether their numbers are right.

As for utility rates: in most of the US, utility rates increase by about 2.5-3.5% per year. Certain places have very low historical increases while others have very high increases. You can get the historical rate of increase from your utility company or by looking back at old electricity bills at the amount you pay per kWh. 

If your solar quote shows a projected increase of more than 3.5%, ask the solar company to show proof that their numbers match the historical rate of increase, or run the savings estimate again using a lower rate. 

Financing

Finally, it’s very important to find out about financing options and their effect on final cost. 

Nearly all solar companies work with financing companies to provide solar loans, which offer low monthly payments rather than a big upfront charge. Other companies will offer solar leasing or power purchase agreements (PPAs), which means the solar company owns the panels and you pay a monthly lease payment or per-kWh charge for the solar energy the panels make. Sometimes, these options will be advertised as "free solar panels," but don't be fooled! You'll still have to make monthly payments.

One important thing to know here is that solar installers who offer loan financing often end up passing a finance charge onto customers who sign up for that financing. You should ask the installer for the cash price vs the financed price, and if the difference seems too great to you, consider using your preferred bank to obtain a HELOC to go solar, equal to the cash price.

HELOCs are harder to obtain than other solar loans, but don’t have finance charges so you’ll save money while still financing the total cost. In addition, solar panels increase the value of your home, so a HELOC won’t necessarily decrease the amount of equity you have in your home as much as it would if you were financing another type of home improvement.

Enter your zip code and amount of your most recent energy bill to see average solar panel costs in your area

Questions about the work being done 

Once you’ve settled on the price and payment schedule, it’s time to think about the practical matter of getting this stuff on your roof and kicking out kilowatts. 

Here are the questions to ask about the installation process:

• What are the steps of the installation process?

• How long will it take to complete the process, and what is the timeline?

• What if you don’t finish the work on time?

• What guarantees do you offer for your work?

• What happens if a leak develops well after the panels have been installed?

Installation process 

These questions are all about the process. A good installer should be able to give you a timeline and commit to meeting it. There are certain things within their control, like initial start dates, and things out of their control, like permitting timelines and scheduling an inspection from the utility company prior to getting final permission to operate (PTO).

In general, it can take as little as two or as many as six months for the whole process to get done. Installers need to do a site visit, submit a system design to the local authority, get a permit, schedule the installation, do inspections, and get final permission to interconnect and operate your system on the grid. 

They should be open with you about what this process looks like and how they’ve worked with your utility company in the past.

Guarantees 

If the installer can’t finish the work on time, it may mean you don’t qualify for incentives that were available at the time you signed the contract. 

A good example of this is back in when the federal solar tax credit decreased from 30% to 26% of costs. Anyone who didn’t have a completed solar installation by December 31st didn’t get to claim the 30% credit.

Your installer should be willing to give you a guarantee or pay the difference between incentives you thought you’d get and incentives you can’t claim because of their going over the time estimate to complete the installation. 

They should also give you a guarantee that their work will not damage your home, and offer protection for you against roof leaks, broken tiles, and other damage. The best installers offer workmanship warranties for at least 5 years after installation so you can feel confident that they do quality work. If any problems occur from shoddy workmanship, they usually occur soon after installation.

Questions about the future 

Now that you’ve squared away info about how and when the system will be installed and how much it will cost, it’s time to think about what happens during all the years you’ll be harvesting energy from the sun. 

Solar panel systems are meant to last for at least 25 years, but things can go wrong, and it pays to be prepared for if that happens.

Here are the questions you should ask about the future:

• How will I be able to monitor the solar energy my system generates?

• What happens if the solar panels don’t produce as much energy as you claim?

• How long will my contract with the utility company last?

• What happens if I need my solar panels removed to have work done on my roof?

• What if a solar panel fails due to a manufacturing defect or breaks because of a storm or other natural disaster?

• What if I want to add additional panels to my installation? What about a battery?

• What happens if I move while still paying off the panels?

Monitoring software and systems 

By the time your panels are installed and fully operational, you’ll be itching to see a real-time readout of just how much energy they’re producing (and how much money you’re saving) at any given time. 

Your installer should be able to tell you about any solar monitoring software they use, or at least show you how to use a third-party solution like the Sense energy monitor to track your solar production and consumption.

If you get solar panels through a PPA or lease, your installer will probably include a production guarantee. That means you should expect a minimum number of kWh per year, and if the leased panels don’t make that much, your contract should have a clause that describes how the company will reimburse you, usually a monthly bill credit. 

When you’re buying solar panels with cash or a loan, you generally won’t get a production guarantee from the installer. That doesn’t mean you should suffer with low power output. If your panels aren’t generating what you think they should, your first call should be to the installer. But even before the panels get up on the roof, ask the company what kind of after-sales service they’ll provide if you run into problems. 

Know your contract 

Be sure to ask about your net metering contract. It used to be that many states with net metering rules allowed those homeowners who signed up to stay on the arrangement indefinitely. 

Now, as net metering changes take place all over the country, you may only be guaranteed the full retail rate for 10 or 20 years. It pays to ask rather than be surprised when your utility switches you to a different plan after a decade or two.

Panel failure and damage 

If a solar panel fails because of a manufacturing defect, you should hear from the installer whether they want you to contact them first or reach out to the manufacturer for warranty repair. The answer to this question will likely be different whether you own the solar panels or lease them. 

Side note: solar panels are covered by most homeowners’ insurance policies. If you own the system and your panels are physically damaged, your insurance company will likely pay for any repairs, minus your deductible. 

Big, structural change 

As we’ve said a dozen times now, solar panels are designed to last for a very long time. 

Unless you get them installed on top of a brand new roof, chances are good you may someday have to remove them and have a roofing company install new shingles or tiles. The very best installers will offer to do this for you for a modest fee, and you may even ask to have them write it into the contract. 

If your energy needs change or your energy usage increases after, say, starting a family or buying an electric car, you may want to consider adding additional panels to your installation someday down the road. It’s very important to ask about that possibility before you get the first panels on your roof, because there may be limitations or other considerations that would prevent you from adding panels in the future. 

For example, you may have limited roof space, and installing some less-efficient panels now would take up the entire available surface. Instead, your installer might convince you to install more efficient panels that take up less space, so there will be room for an expansion in the future. 

Additionally, the possibility of adding solar panels in the future may lead your installer to recommend an inverter rated to handle more power, or to recommend microinverters, which allow for future panels to be added without making modifications to your existing setup.

The final word on asking a solar installer questions 

Choosing to install solar panels on your home is a big deal, and if you’re like most people, you’ll want to make sure you’re making a smart choice and asking the right questions. 

You don’t have to ask every question we outlined above, and you can do a lot of your own research right here using the “learn solar” menu (to the right on desktop or by clicking on the “+” button on mobile.

Whatever questions you do ask, your installer should have a good, logical answer for, and they shouldn’t have any problem answering. You can tell the difference between a good and bad installer by how willing and open they are about answering all your queries. 

Solar panels represent the ideal of a low-maintenance product, and once yours are fully installed and activated, you may never have to contact your installer again. Still, you’re about to enter into a 25-year relationship with a company, so you should make sure they are ready to be there for you. 

That depends on what you’re spending on electricity, the amount of power that an installed solar photovoltaic (PV) system can provide, your finances, and your time frame for living in your home.

Calculate your average monthly electric expenses by tallying your electric bills for the past 12 months and dividing by 12. Plug that figure, and your address, into a solar calculator such as Google Project Sunroof, EnergySage, or SolarReviews. Those tools will combine that information with aerial views of your roof from Google Earth, Tesla Maps, or another aerial photography tool to estimate how big a PV system your home could handle, how much you could save over, say, 20 years, and your investment’s break-even point: that is, when a purchase would begin to pay off. The average homeowner who buys a solar panel system could break even in 8.7 years, EnergySage says. 

Savings and break-even estimates for the same property can be wildly different among the calculators, so consider them a starting point in your decision-making. But if you plan to sell your home before the earliest break-even point, a solar purchase probably doesn’t make sense.

If your roof is old, the answer is no—at least not until you replace it. Asphalt shingles that are 10 years old or more should be replaced before adding a solar array on top, says Ana Almerini, a spokesperson for SolarReviews. New solar panels are warrantied to last, on average, 25 years, while most roofs are warrantied for 30 years or less. If your 10-year-old roof needs to be replaced at its 30-year mark—20 years into your solar array’s lifetime—you’ll need to remove everything to reroof and then reinstall the solar system, a costly proposition.

With newer roofs, you’ll still only know for sure if a solar installation is feasible after a solar company rep checks out your roof and surrounding foliage in person. They’ll determine whether there’s too much shade or other obstacles, or the roof has problems that don’t make an installation worthwhile. That inspection costs you nothing and takes place before you sign on the dotted line. Or, If you’d rather find out whether your roof is a candidate before you shop—avoiding the calls, texts, emails, and visits to your front door you can expect from aggressive salespeople—pay a roofer for an inspection. 

Check, too, with your municipality—and homeowners’ association, if you have one—to find out about any restrictions on the type and placement of solar panel arrays. 

The most powerful savings tool for homeowners who buy their solar systems is the federal solar tax credit, available for installations through . It allows you to subtract 30 percent of the cost of buying and installing solar heating, electricity generation, and other solar home products from your federal taxes. There’s no dollar limit on those expenses; you’re entitled to that 30 percent tax break whether you spend $20,000 or more than $100,000 on costs associated with a residential solar system.

This break is available to all taxpayers for their primary or secondary residence located in the U.S. Taxpayers of any income level can take advantage of it. You can use it whether you itemize your taxes or take the standard deduction. Keep in mind, though, that the solar tax credit is available only if you purchase a solar system; if you lease one, you can’t take advantage of the credit. And if you don’t typically owe taxes, the credit isn’t useful.

You also could further your savings in these ways: 

Local and state incentives. Your state may offer additional breaks, including tax rebates or sales tax exemptions (see this state-by-state compilation from Solar.com, an online solar marketplace). Your municipality may exempt your solar system from your home’s assessed value, so your taxes don’t rise even as your home value does.

Rebates. Your electric utility, as well as certain installers and manufacturers, also may offer rebates for buying and installing a system. 

Sale of your excess electricity. In a handful of states, solar-home owners can arrange to sell their excess power to utilities. They sign up with a marketplace that assigns the excess electricity a certain number of solar renewable energy certificates (SRECs); those SRECs are then traded in a marketplace with fluctuating prices. The District of Columbia and eight states—Delaware, Illinois, Maryland, Massachusetts, New Jersey, Ohio, Pennsylvania, and Virginia—have such marketplaces. In some areas of Michigan, Indiana, Kentucky, and West Virginia, residents can participate in Ohio’s SREC marketplace.

Leasing is commonly marketed as a way to finance a solar installation for those who aren’t using cash. The benefit of leasing—usually a 20-year commitment—is that you put no money down. Your energy bills are instantly lower, based on a formula the solar provider devises. Maintenance is handled by the solar company as well. Typically you pay a set monthly amount for electricity— regardless of how much power your system produces. (In a power-purchase agreement, a lease variant, you pay for what your system produces.) 

Just be aware of the pitfalls and caveats of leasing, which make this type of financing less beneficial to homeowners than cash purchases or loans. For one, the solar panels, racks, and inverters on your roof aren’t yours, and the solar company that owns them—not you—benefits from all the available tax incentives. Interest rates can be higher than for financing you obtain yourself. Your monthly payment also can rise each year with a lease, versus a loan payment that stays constant. 

And, depending on where you live, your home could be more difficult to sell with a leased solar system in place. If the new buyer doesn’t want to continue the lease, the solar company will remove its panels and you’ll have to pay what you still owe on the lease. Buyers who agree to assume the solar lease need to report those payments as their own debt when applying for a mortgage, added to any credit card balances, student debt, and car loans they already owe. “That lease payment could throw the buyer into a higher interest rate, or not qualify them for a loan at all,” says Sandra Adomatis, a real estate appraiser in Punta Gorda, Fla., and an expert in valuing green homes with The Appraisal Institute, an industry group. 

Taking a loan from the solar company also isn’t ideal. The interest rates the solar company will charge may be higher than what you’d get by seeking an independent lender yourself. And solar dealers often tack on significant origination fees—up to 30 percent of the system’s cost, compared with 1 to 5 percent for traditional loans. “I wouldn’t use the financing from the solar company,” says Garrett Mendelsohn, founder and CEO at Solar Bootcamp, based in Palmas del Mar, Puerto Rico, which teaches solar company representatives how to sell systems virtually. “Ninety percent of the time, you’re paying a high interest rate and huge dealer fee.”

If you’ve been in your home a while, a less costly way to finance your solar investment is through a home equity loan or home equity line of credit (HELOC) or loan, borrowing off your home’s built-up value. The interest rate is likely to be lower than if you seek a personal loan for the job. And, you can deduct the interest on your federal tax returns for a major solar installation; the IRS permits such deductions when home equity is used to “substantially improve” your home.

For HELOCs and other types of loans, consult comparison sites like Bankrate, Lending Tree, and SoFi for competing interest rates and terms. New-home buyers and those refinancing also can check out Fannie Mae’s HomeStyle Energy Mortgage Program, which can help you bundle a solar loan into the new mortgage. 

After closing, keep an eye on interest rates. You can refinance when current rates, now relatively high, begin to fall. 

Solar installers are typically one-stop shops, offering you panels and inverters—and the racks that hold them—as well as installation. In addition to offering their own financing, they may sell extra warranties, monitoring, and maintenance. 

To find installers, search for “solar installer,” or input your address and other basic personal information into comparison websites like EnergySage and SolarReviews; each analyzes the quality of local providers and their products using technical measures; they both also use consumer reviews. (EnergySage doesn’t require your number, a boon if you want to avoid texts.)

The not-for-profit Consumers’ Checkbook is another source of reputable installers, providing reviews of local services in seven major metro areas—Boston, Chicago, the Delaware Valley, Puget Sound, San Francisco, the Twin Cities, and Washington, D.C. In the Bay Area—subject to California’s relatively new mandate that new, low-rise residential construction include solar photovoltaic systems—Consumers’ Checkbook has reviews on 132 solar contractors. 

Before you arrange for an in-person or Zoom consultation from companies you identify through these tools, ask providers to show proof that they’re licensed in your state and municipality to do the work where you live. Check, too, with the Better Business Bureau in your area for complaints. Confirm that the companies have been certified by the North American Board of Certified Energy Practitioners (NABCEP), a trade organization that sets standards for solar installers. Your utility company or state energy board also may list providers that meet certain quality standards. The New York State Energy Research and Development Authority (NYSERDA), for instance, offers a search for solar contractors with a “Quality Solar Installers” designation. 

Neighbors with recent installations might be willing to talk to you about their experiences with solar contractors. Or, ask for input through community forums like NextDoor and the Facebook page for your community. And when you contact a company, find out how long they’ve been doing solar installations. Choose a company with several years’ installation experience, and ideally a presence in more than one state, Mendelsohn advises. He also recommends finding a company that uses its own, in-house installers.

You’ll see lots of figures and factors in a solar proposal. But there are five really worth focusing on when comparing offers.

Price per watt or kilowatt. That’s the upfront cost divided by the size of the system. The lower the cost per watt, the better the system’s value. You can use each company’s estimated cost per watt to compare proposals. “It’s like unit pricing at your supermarket.” explains Vikram Aggarwal, EnergySage CEO.

Warranties. They may differ for the workmanship, the solar panels, and the inverters—that is, the mechanisms that take the direct current (DC) that the solar panels create and convert it to alternating current (AC) electricity that our homes use. A standard solar panel warranty is 25 years, Aggarwal says. Inverter warranties range from 10 to 25 years.

Rated power. This is a measure of the system’s efficiency—that is, how much electricity it puts out under ideal conditions. Rated power of at least 400W is preferable; Aggarwal recommends 420W to 440W, because he says it’s the most efficient. The solar company should also give you a projection of how much the power production will degrade by the time the warranty expires. Solar panels’ productivity degrades at a median, 0.5 percent a year, according to the Department of Energy’s National Renewable Energy Laboratory. At the end of a typical, 25-year warranty, that translates to productivity of 87.5 percent.

Annual production. You may notice that the proposals you get from different companies show dramatically different estimates of the amount of power they can provide—from, say, 100 percent of your current needs to 125 percent or more. Why bother with all that excess power? If, say, you add an electric vehicle to your power consumption, planning for more power may be worthwhile. “If you think you’re going to buy an electric car in next four to five years, you may want to oversize your system now,” Aggarwal says. “Most installers won’t be willing to add new panels and inverters in the future.” Depending on the arrangement with your utility, you may be able to sell back the excess power, reducing your electric bill further. 

Quality of the solar equipment. You can look on EnergySage and SolarReviews for comparisons and judgments of solar panels and inverters; names like Canadian Solar, LG, and QCel show up highly rated there. For inverters, experts we talked to preferred microinverters, individual units attached to each panel, versus string inverters, which are connected to both the panels and each other like Christmas lights. As with Christmas lights, string inverters are annoyingly interdependent. “If one panel goes out, Aggarwal says, “the whole system goes out.”

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