Installing Solar Panels on a Flat Roof (3 Tips to Optimize Output)
In this guide, you’ll learn:
- How to maximize solar panel performance on a flat roof
- Whether solar installations cost more for flat roofs
- What solar equipment you’ll need for a flat roof
The optimal angle for solar panels in North America is between 20 and 45 degrees toward true south, usually depending on your latitude. However, solar panels can still be a worthwhile investment even if you have a totally flat roof.
In this article, we’ll discuss how efficient panels can be on flat roofs, the cost of a flat roof solar panel system and more. We’ll also offer four tips for saving money upfront and over time on your flat roof solar array.
Can You Install Solar Panels on a Flat Roof?
Yes, you can usually install photovoltaic (PV) panels on a flat roof, although the installation does come with some challenges that might make it impractical.
Most importantly, solar panels generate the most electricity for your home when they receive direct sunlight. The more direct the sunlight is when it hits the face of the panel, the more power it will generate in all conditions. Of course, a higher level of production translates to greater energy savings over time.
It’s not entirely clear what kind of power production differential you’ll see between flat and angled panels, although most estimates suggest between 30% and 50% less energy from flat panels.
Even considering the reduced energy production of flat panels, installing a solar energy system on a flat roof can still be beneficial and, in some cases, save you even more money than going solar with a standard angled roof. We’ll discuss how in greater depth later on.
For now, the table below should illustrate how much of a difference you might see in solar production based on the angle at which your panels are installed. Since the optimal panel angle is based on your latitude, the table assumes you’re located at around 40 degrees N, which is about the center of the United States.
|Panel Angle||Expected Power Loss Compared to Optimal Angle|
|40 degrees (about optimal at 40 degrees N latitude)||0% (optimal)|
|0 degrees (flat)||30%|
|-40 degrees (North-facing panels)||~50-80%|
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Benefits of Installing Your Solar Panel System on a Flat Roof
As mentioned above, there are some benefits to installing panels on a flat roof as opposed to one that’s angled. You could pay less for a flat-roof system, and you could run into fewer restrictions with respect to the orientation of your panels. We’ll explain each of the benefits of a flat-roof installation below.
- Potentially lower installation cost: Flat-roof systems can sometimes cost less than angled-roof systems, depending on the type of racking equipment used for the installation. Ballasted racks—which we’ll discuss in greater depth later—can sometimes be more affordable than a typical mounting system. Plus, the installation on flat roofs is inherently safer and could end up being cheaper due to a faster installation time and no need for safety equipment.
- Potential for larger system: With an angled roof, you lose about 50% of your roof space if your home faces north or south, as one half is angled away from the sun and typically isn’t viable for solar panel placement. With a flat roof, you don’t run into this issue, so you could potentially be able to fit a much larger system on your roof. This could mean greater savings for your home or place of work, especially if you have an energy consumption rate that is above average.
- Potential for longer system life: Solar panels on slanted roofs have quite a long lifespan in most cases, with equipment warranties averaging around 25 years and some panels lasting upwards of 30 years. Continuous changes in temperatures—especially at the extremes—can put added wear on the electronics inside your PV panels. Flat panels receive less direct sunlight, thereby seeing less drastic temperature changes and potentially lasting even longer than those installed at angles that are ideal for maximizing production.
- Panels won’t get as hot: As mentioned above, flat panels won’t typically get as hot as those installed at an angle toward the sun. This could increase their lifespan, but it also minimizes the reduction in efficiency from the inopportune angle. High temperatures can reduce efficiency by up to 25%. While the intensity of sunlight hitting flat panels will be lower, efficiency loss to heat will also be reduced, meaning flat panels are only slightly less efficient in some cases than those installed at an angle.
- Installation can be done without roof penetrations: Traditional angled roofs require roof shingle penetrations to install the racking system, and this naturally increases the risk of roof leaks. Flat-roof PV systems can be installed using penetrations as well, but they can also use a ballasted mounting system, which uses weights to keep the system in place. This keeps the risk of roof leaks low, which is great since flat roofs are naturally more prone to leaking.
- No concern for property orientation: Finally, if you have a pitched roof, you’ll be limited in the direction your panels can face. If your roof slopes are angled to the east and/or west, your production is naturally going to be lower than if your roof slope faces south. If you only have a slope facing to the north, you’re in an even less beneficial position. With a flat roof, it doesn’t matter which direction your home faces because you can always install angled mounts to direct the panels to the south.
Challenges of Installing Your Solar Panel System on a Flat Roof
Of course, there are some challenges that will need to be considered when it comes to a flat-roof solar installation. We’ll discuss each of the potential complications of installing solar on a flat roof below.
- Production will be lower: First, as mentioned above, flat panels don’t get the same sunlight intensity, which means production is lower. This could be an issue if you’re looking to keep installation costs down but still maximize power production.
- Panels naturally get dirtier, reducing efficiency: Angled panels are considered “self cleaning” because they naturally get washed every time it rains. The angle allows the water to flow off of them, clearing off dirt, pollen and other debris. Flat panels see a much higher concentration of debris because they don’t get washed naturally. Over time, that build-up will reduce production and, in turn, your energy savings. You’ll either have to wash the panels yourself or pay for ongoing panel maintenance to maintain the highest level of efficiency possible.
- Flat panels are more prone to water damage: If your panels are mounted parallel to your flat roof, water will naturally pool on top of them, and they’ll more easily collect and hold snow in the winter. This leaves them more prone to water damage, which can reduce panel lifespan in some cases. In fact, many manufacturers will waive the 25-year equipment warranty they normally provide if panels are installed flat.
- Fewer solar contractors available: Finally, while most homeowners have access to tons of solar installers that can install panels on an angled roof, there are far fewer solar installation companies that specialize in flat roof applications. We recommend going with a company that has experience installing on flat roofs, especially given the nuances and potential downsides we’ve mentioned above. In some areas, you may not be able to find any providers that can or are willing to install a flat-roof solar array.
- Higher chance of shading: While any roof can be shaded from sunlight from trees or nearby buildings, flat roofs come with some additional obstacles that can cast shade. These include parapet walls, roof vents, HVAC equipment and more. Panels should be installed away from parapet walls and other protrusions to prevent shading during sunlight hours.
Will You Need Special Equipment for a Flat Roof Solar Panel Installation?
Solar installations on flat roofs can be done using three different racking systems: a traditional rack that gets mounted to the roof using penetrations, an angled rack that uses the same method and a ballasted rack that gets held in place using weights.
The mounted rack that holds your panels parallel to your roof won’t provide the greatest efficiency due to the angle of your panels with respect to the sun, but it is the most affordable option. The cost is typically a little less than a traditional installation on an angled roof because the roof is more accessible, and the installation crew often won’t need to maneuver safety equipment around, which can speed up the work.
The angled rack is also similar to what an installer would use on a sloped roof, but it includes additional braces to hold your panels up at an angle. This solar panel mounting system design isn’t unlike what you’d see on a ground-mounted solar array. It’s just as easy to install, but it’s a little more expensive, as the materials cost more.
The ballasted mounting system holds your panels at an angle as well and relies on gravity to keep the array in place. This option may not be realistic in areas that see extreme winds—like during hurricanes or tropical storms—and may require seismic anchors in areas where earthquakes could put the system at risk of shifting off the roof. Ballasted mounting systems are the most expensive of the flat roof mounting options.
The table below includes a quick breakdown of all of the equipment you need or could opt for in flat and sloped roof applications.
|Equipment||Flat Roof||Sloped Roof|
|Angled Roof Mount||Optional (recommended for maximizing solar production)||N/A|
|Backup battery storage||Optional (recommended in areas with frequent blackouts or no access to net metering)||Optional (recommended in areas with frequent blackouts or no access to net metering)|
|Squirrel & Bird Guards||Optional (strongly recommended for flat-mounted panels close to the roof)||Optional (strongly recommended)|
Do Flat Roof Solar Systems Cost More?
The price of a flat roof solar array averages around $23,940 before any incentives or $16,768 after the federal investment tax credit (ITC). Your costs depend on two primary cost factors, though, which can bring the total price above or below what you’d expect to pay for a standard sloped-roof system. We’ll briefly discuss these factors below and how they can affect your pricing.
The first cost factor to consider is the type of mount you choose. If you don’t mind a loss of potential power production, then a flat-mount rack that keeps your panels parallel to your roof will likely lead to a lower overall price than you’d pay with a pitched roof. The process for installation is easier and faster, and there’s less risk involved for the installation crew. The difference won’t be huge, but somewhere between $500 and $1,000 less is possible.
However, if you choose an angled mounting rack, your price will likely be around the same as it would be for a sloped-roof system. A ballasted rack, on the other hand, will probably bring your total a little higher than a system on a sloped roof. Ballasted racks come with higher material costs, so the total is higher even though the installation is easier.
Efficiency of Your Panels
The efficiency rating of the panels you choose will also play a role in your installation costs. If you don’t have the ideal tilt angle toward the sun, you’ll undoubtedly see a lower rate of energy production. If you want or need to make up for that loss, you might have to opt for high-efficiency panel brands.
Something like Maxeon panels, which hold the record for panel efficiency at 22.8%, might suit you best and be required to offset your energy needs. However, these panels come at above-average prices, which could drive up the cost of your array.
If you don’t need to maximize your efficiency to make up for the loss, then any tier-one brand could be chosen, which shouldn’t affect your pricing much as opposed to a sloped-roof solar power system.
Generally speaking, both a flat roof and a sloped roof can be great options for solar systems. Flat roofs can be cheaper or may demand a higher upfront payment to get angled equipment, but they can also come with greater panel longevity and less of a risk of roof leaks. It’s difficult to say if there is one option that’s better or more affordable in the long run than the other.
Solar Installation Cost Factors: Flat Roofs vs Sloped Roofs
The total installation cost for your solar PV system on a flat roof can vary for a few reasons, including differences in labor costs, material costs and more. We’ll include a list of all of the most important cost factors below and explain how each is affected by the type of roof you have.
- Solar panels: Of course, the panels you have installed, regardless of the type of roof you have, will make up a significant portion of your installation costs. Panels are an essential part of all solar arrays, and the cost of the panels usually isn’t dependent on the type of roof you have. However, as mentioned above, some solar customers will need to choose a higher-efficiency—and more expensive—panel for flat roof applications, given the potential loss of production.
- Installation labor: The labor to install your solar system will also be a big chunk of the total cost. The labor for a sloped roof will typically be a few thousand dollars higher because access to the roof isn’t as convenient, and the crew may need to work with safety equipment, which can slow down the process.
- Mounting equipment: Mounting equipment for an installation parallel to the roof will usually cost at least $1,000, but a flat roof installation using a ballasted rack could cost around five times that amount.
- Accessories: Accessories for your panels, including squirrel guards and snow guards, are optional and can add around $2,000 to your installation costs. The cost won’t vary much by roof type, although snow guards—which are meant to prevent heavy snow from sliding off of your panels and onto the ground below—are typically not even offered for flat roof systems. While snow guard installation is up to you, we strongly recommend installing squirrel guards, which can prevent damage to your wiring and nesting under your panels.
- Wiring and conduit: Your panels need to be wired and connected to your inverter, and wires are often run through electrical conduit. This equipment is necessary for both flat and sloped roof applications, and the cost won’t vary at all.
- Permits: All municipalities in the U.S. mandate solar panel permits, electrical permits, building permits or some combination of the three for solar installations. These typically cost a few hundred dollars, depending on where you live, and the price shouldn’t be affected by the type of roof you have.
The table below includes a quick breakdown of the installation costs you could be looking at for your system, depending on your roof type.
|Cost Factor||Flat Roof||Sloped Roof|
|Solar Panels||$5,000 – $10,000||$5,000 – $10,000|
|Mount (optional)||$1,000 – $5,000||$1,000|
|Accessories (optional)||$0 – $2,000||$0 – $2,000|
|Wiring and Conduit||$500 – $1,000||$500 – $1,000|
|Permits||$200 – $1,000||$200 – $1,000|
|Total||$9,700 – $22,000||$11,700 – $20,000|
You can click the links below to get a more accurate estimate for your specific home from a reliable solar installer in your area.
6 Ways You Can Save Money When Installing Solar Panels on a Flat Roof
Since installing a PV system on a flat roof can be more expensive than on a traditional solar roof, many solar customers with flat roofs look for ways to save money on their conversion. There are a few things you can do to keep costs down upfront and in the long run, including the following:
- Choose a high-efficiency panel brand
- Invest in a solar battery
- Choose an installer with experience in flat roof applications
- Choose the right mounting system for your property
- Take advantage of solar incentives
- Get multiple quotes for your system
We’ll explain how these factors can save you money in the following sections.
Choose a High-Efficiency Panel
All solar panels come with an efficiency rating, which tells you the percentage of sunlight your panels can capture and convert into electricity for your home or commercial building. The higher the efficiency rating, the more expensive your panels will be, but they’ll generate more power over time.
While choosing high-efficiency panels will cost you more upfront, it can save you quite a lot more over time, especially if you choose to save money by having your panels installed flat against your flat roof. Higher efficiency ratings translate to greater savings on your electric bills over time, which will eventually be financially worthwhile.
Invest in a Solar Battery
A solar battery like the Tesla Powerwall will store excess power produced by your panels for later use, usually when your solar array fails to provide sufficient power for your home at night or on cloudy days. Underproduction is more likely on a flat roof system if you install panels with traditional equipment that leaves them lying parallel to the ground.
While a solar battery will also drive up your upfront system costs, it can end up saving you money over time by helping you avoid high electricity costs. This is especially useful if you don’t have access to net metering in your area, as you can potentially offset all energy consumption in your home, even if your panels are installed flat and provide less power overall.
Solar batteries will also continue to provide energy to your home through power outages, which is an added bonus.
Choose an Experienced Installer
We always strongly recommend choosing a solar installer that has at least five to ten years of experience in the industry, as this can help avoid issues with the installation process that could leave you with property damage or a malfunctioning system.
If you’re installing panels on a flat roof, it’s critical that you hire a company that has experience specifically with flat roof applications.
Since flat roofs are more prone to leaking, can include different mounting equipment and potentially demand a higher-efficiency panel chosen for your specific system, an experienced flat-roof installer can make a world of difference and end up saving you money on repairs or energy bills in the long run.
Choose the Right Mounting System
As we mentioned above, there are three different mounting options for solar arrays on flat roofs. There isn’t one that’s best in all situations since the right option depends on your power needs, the size of the system you can or want to install, personal preference, budget and more.
A typical mounting system will cost the least but will yield lower overall production, which won’t be ideal if you have above-average energy consumption rates in your home. Likewise, an angled mounting system will be more expensive upfront and may not be worth it if you use less electricity than the average home in your area.
Your mounting option should be chosen carefully so you don’t overspend upfront or undersave over time.
Take All the Solar Incentives You Can
One of the best ways to save money on your flat-roof solar installation is to take all of the incentives you can. There are multiple benefits available to most homeowners to incentivize solar adoption and reduction of emissions.
Most importantly, all U.S. residents have access to the federal credit, which can effectively reduce your installation costs by around 30% if your tax burden allows for the entire credit to be taken within five years.
Other incentives to look for include state tax credits, solar rebates, net metering, solar renewable energy credit (SREC) programs, creative financing options and more. You can check the Database of State Incentives for Renewables and Efficiency (DSIRE) for more information on what programs and incentives are available to you.
Get Multiple Solar Quotes
Finally, we strongly recommend getting multiple quotes for your installation. Having estimates from a few different companies lets you compare the overall pricing, the installation options they recommend for your home and more, and then choose the one that suits your needs and your budget best.
Some companies may also offer discounts or perks—like free or reduced-cost add-on equipment—to entice you to go with them if they know you’re shopping around.
Just remember to get all of your quotes from companies that have experience with flat-roof solar installations.
What Are the Steps to Install Solar Panels on a Flat Roof?
Installing solar panels on a flat roof is pretty similar to the installation process for a sloped roof, although there are some nuances concerning the mounting equipment. We’ll include a brief description of each step of the process below.
- Get a quote: Your first step will be to get a few quotes from local installers, assuming you’re not going to attempt an installation yourself. This process usually involves a representative coming to your home to measure your roof and inspect your property and then designing a clean energy system that fits your home and suits your energy needs.
- Sign the contract: Once you choose the installer that you believe will serve you best, you can sign the contract and get the preparation phase underway.
- Wait for permits and inspections: A big part of the prep phase will be waiting for building or electrical permits to be approved, which may involve an inspection from your building department. Your installer should also be ordering any equipment needed for your system that isn’t in stock while waiting on planning permission.
- Installation: Once the permits are approved and your equipment is delivered, your installer will schedule the installation. You should plan on being home on the installation day to provide access to your electric meter and electrical panel. The installation typically takes between five and ten hours, depending on the system size and the mounting equipment involved.
- System connection: Once your panels are installed and any post-installation inspections are completed, your solar company will connect the system to your home and activate them. At this point, your solar array should be providing power to your home and begin offsetting your energy bills.
- File for incentives: After the installation is done, your installer should file any necessary paperwork for you to take incentives available, including the federal credit, net metering and more.
- Enjoy your energy savings: Finally, your installation is completed, so you should see your energy bills decrease or disappear entirely.
DIY Installation of Flat Roof Solar Systems
It’s possible to install a solar system on a flat roof yourself, although we generally don’t recommend it. Flat-roof solar applications involve some nuances that demand a professional installation.
First, mounting your panels using traditional mounting equipment involves penetrating your roof materials, which greatly increases your risk of roof leaks. Flat roofs are already more prone to leaking due to the risk of water pooling, so drilling holes in your roof with no experience is inherently dangerous.
If you opt for a ballasted mounting system, it’s easy to avoid roof leaks yourself. However, getting the mounting equipment up to your roof can be dangerous, and you should consider the load your roof can safely handle.
Additionally, some manufacturers only provide warranties for their equipment if it’s installed by a certified professional. If you choose a flat mounting system, most will void the manufacturer’s warranty because of the risk of water pooling on the equipment. A professional installer should help you avoid voided warranties either by using a more appropriate mounting rack or choosing a panel brand that doesn’t void warranties based on panel orientation.
Overall, solar installations for flat roofs are more DIY friendly than they are for sloped roofs because you have the option of buying mounting equipment that doesn’t require roof penetration. However, we still recommend hiring a professional that can size your system for your energy needs and deliver higher-efficiency panels that might be necessary to maximize the value of your flat-roof system.
You can use the links below to get free quotes from experienced and trustworthy solar installers in your area.
3 Tips to Maximize Your Solar Panels’ Efficiency on a Flat Roof
Since system production on a flat roof is often lower than you’d see on a sloped roof, many customers with flat roofs need to do everything they can to ensure ample production from their systems. There are three things you can do to get more power out of your panels:
- Choose an angled mounting system
- Choose a high-efficiency panel brand
- Choose a panel with a good performance warranty
We’ll discuss these in greater depth below.
Choose an Angled Mounting System
As mentioned above, panels generate the most power when they receive intense sunlight, which happens when the solar cells are placed at the optimum angle to be exposed to the most sun. If you install your panels flat against your roof, they’ll produce a fraction of what they would with an angled mounting system or an angled ballasted system.
You’ll spend more on angled equipment, but it’s often worth it in the long run because of the boost in energy savings you’ll enjoy. On average, an angled system can lead to a bump in production of around 30-50%.
Choose a High-Efficiency Panel Brand
A high-efficiency panel brand will produce more electricity in all conditions than a panel with a lower efficiency rating. This is the case for systems on flat roofs and sloped roofs. Over time, that boosted production will save you more on your utility bills, so the higher upfront cost eventually pays for itself.
A high-efficiency panel is especially important if you’re installing panels flat against your roof. Since you’ll see a lower production rate due to the lower sunlight intensity, making up for some of that loss by maximizing panel efficiency might be necessary.
High-efficiency panels usually cost more, but again, it could be worth it over time to spend more initially.
Choose a Panel With a Good Performance Warranty
Finally, you can maximize the long-term production of your flat-roof system by choosing a panel that comes with a good efficiency warranty. Most of the tier-one panels include this coverage, which guarantees that your panels won’t lose more than a specific amount of their efficiency over the warranty term—often no more than a 20% loss over 25 years.
The better your efficiency warranty, the more power your panels will generate over time and the more money you’ll save on electric bills.
Bottom Line: Will Your Flat Roof Accommodate a Solar System?
Installing solar panels on a flat roof is almost always possible and still makes good financial sense. You’ll have to choose the mounting option that’s right for your property and energy needs, but provided you pick the right one and get panels with a good efficiency rating, a flat roof solar array can be an outstanding investment. Plus, some mounting options could end up being more affordable than an installation on a sloped roof.
It’s possible to install panels on a flat roof yourself, but since there are a few important things to consider—like the mounting option and panel efficiency that makes the most sense for your budget and energy needs—we suggest hiring a professional. Getting multiple quotes from companies that specialize in flat-roof solar applications can help you save money and keep the risk of roof leaks, poor panel performance and inadequate production to a minimum.
You can use the tool below to get quotes from reliable installers in your area that handle flat-roof solar installations.
FAQs: Solar Panels on Flat Roofs
In the sections below, we’ll provide answers to some of the most common questions we see about solar installations on flat roofs.
“Dead load” refers to the weight of your panels, mounting equipment and ballast, if applicable. Basically, dead load tells you the entire mass of your solar array, and it’s often used to determine if your roof structure can safely support your system. The actual dead load will depend on many factors, including your mounting equipment—ballasted mounts will weigh far more than other options—the size of the individual panels, your system size and more.
It’s critically important to ensure that your roof can support the dead load, as major building damage or even collapse can occur if it can’t. This is one reason we strongly recommend having a professional handle your flat-roof solar installation, especially if you’re using a heavy ballasted system.
In the U.S., angling your panels to the south is the best option, as this leads to the highest sunlight intensity on your panels and the greatest production rate. You can use an angled mounting system or an angled ballasted system to get your panels to face south on your flat roof.
Designing the actual system involves getting the right number of panels installed while considering HVAC equipment, roof vents and other protrusions you might have on your roof. This is yet another reason why we recommend hiring a professional to handle the installation.
There are many factors involved when calculating the weight needed to hold a ballasted system against your flat roof. These include average and maximum expected wind speeds in your area, the angle of the panels on your roof, the weight your roof can support and more. There is no universal number that works for every flat-roof system. This is another reason we recommend hiring a professional to tackle any flat-roof solar projects.
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