Checking your roofs compatibility with solar panels
Roof-mounted solar is popular for its versatility and efficiency. As technology of solar panels continues to improve, so does mounting hardware. It’s never been easier or more affordable to attach solar panels to your roof. What should you keep in mind when planning for a rooftop installation? From shading to the most efficient direction for mounting, here’s what to plan for.
What is a roof-mounted solar panel system?
Roof-mounted solar panels are available in both flexible or rigid forms. Both panel types are secured to the roof of your home, RV, or van with bolts, brackets, and mounting hardware. Rigid panels are the most durable option. Renogy’s roof solar panels mounting include a corrosion-resistant aluminum frame that is great for extended outdoor use, allowing the panels to last for decades. Renogy’s flexible panels offer a low-profile look and are lightweight and easy-to-handle.
What is the best roofing material for mounting solar panels?
Solar panels can be mounted on clay tile, metal standing seam, asphalt, EPDM rubber, and TPO and PVC. Wood shake and slate tile roofs present some unique challenges. We encourage you to consult with a professional about mounting to those surfaces.
What should I consider when evaluating my roof solar panels?
Is my roof too old? You’ll want to make sure your roof is in suitable shape to hold solar panels and that it isn’t due for a replacement. If your roof is nearing the end of its lifespan, you’ll want to replace your roof before installing solar. A solar panel system will last you 30 to 35 years. If your roof is between five and 10 years from needing replacement, it’s a good idea to hire a professional to assess the condition of your roof. How long do roofs last? Every roofing material has a slightly different lifespan. As some general guidelines, clay tile, slate, and copper roofs can last up to 50 years, wood shake roofs have about a 30 year lifespan, and cement shingles last about 20 years. Replacing your roof before installing solar means you won’t have to tear everything out just a few years into having your installation, which will save you lots of money in the long run.
Which is the best direction to install solar panels? Typically, solar panels work best on a south facing roof. When panels are pointed east, they produce a lot of energy in the morning, but very little in the afternoon. The reverse is true if they face west. Solar panels will receive almost no direct sunlight if they are facing north. Solar panels actually work best when they’re facing true south, which is slightly different from magnetic south. We recommend using Google Maps to look up your property, display the grid, and see which direction true south is. If you can’t mount your panels to be at true south, southeast and southwest-facing panels will also work.
Is shade an issue? Although the output will be greatly reduced, solar panels will still work in the shade, just at a lower capacity. A general rule of thumb is that solar panels will produce about half as much energy as they would with direct sunlight. Trees located to the north of your home will typically pose the least amount of shading obstruction for panels. Trees planted on the south side can block midday sun, which is a crucial time for solar power production. Your roof itself can also present shading challenges. Dormers, gables, and chimneys in particular can obstruct sunlight from your panels, as well as create some obstacles for mounting your solar panels themselves.
My roof is flat. Can I mount solar panels to it? Solar panels can work on both flat and sloped roofs. If you have a sloped roof, the best angle is between 30 and 40 degrees. Any steeper and the performance of your panels will not be efficient. In order for the panels to be self-cleaning, they should be at a minimum of 15 degrees.
Do I have enough room for roof solar panels? You’ll also need to make sure you actually have room on your roof for solar panels. A large, rectangular roof with no chimney or vents is, of course, ideal for solar rooftop installation. This can be somewhat rare, but you’ll want to make sure that you have enough space for the amount of panels you need to meet your energy needs. If you haven’t already, use the Renogy solar panel calculator to determine how many solar panels you’ll need to meet your energy needs.
Will my HOA allow it? If you live in a subdivision governed by an HOA, you may not get the last word about your solar panel installation. Many HOAs have regulations governing the outer structure of homes, roof included. If you’re considering a rooftop solar installation, you can reach out to your HOA beforehand to see if it has an existing policy on solar panels. The HOA will be able to provide you with its guidelines and point to the specifications that must be adhered to.
What if my roof is not suitable for solar?
If after considering all the above factors, you come to the conclusion that your roof is not suitable for solar panels. You can either install a ground-mounted solar panel system elsewhere on your property, purchase a portable solar panel kit if you have smaller energy needs, or build a solar panel carport to create a surface to mount your panels, as well as shade your car.
Will solar panels damage my roof?
No, not if your solar panels are mounted properly. It’s true that mounting roof solar panels does require the right mounting hardware in order to safely and securely attach the panels to your roof. However, if done correctly, solar panel installation should not damage your roof or the surrounding structure. Additionally technology has continued to improve where mounting solar panels has never been easier. In some cases, solar panels can actually protect your roof instead of inflicting any sort of damage.
Roof solar panels installation conclusion
Roof-mounted solar panels give you the ability to generate energy with a secure and powerful system. By taking into consideration your roof age, direction, shading, slope, and space, you’ll be able to accurately determine if a roof-mounted solar system is right for you.
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Orientation. How it affects solar panels
North-facing panels will usually give the greatest energy output. That’s because Australia, being in the southern hemisphere, experiences a sun that is mostly directed from the north. But did you know that facing west will only reduce your solar system’s total annual energy output by about 15 per cent (depending on where you are located and the tilt of your solar system). And this might just be a Smart decision.
As you can see from the above graph, North at 30’ tilt is optimal for Sydney to generate the maximum amount of energy over the whole year.
But for many households, maximum solar energy production does not always equate to optimal power saving the most money off your electricity bills.
Firstly you need to know if you are on a flat electricity tariff. you pay the same rate for your electricity regardless of the time of day. or if your rate varies. Electricity networks such as AusGrid, CitiPower, Ergon are encouraging variable or time-of-use pricing.
The major cost in electricity bills (accounting for roughly half), is in fact the poles and wires, which need to be sized to meet peak demand. Hence the push to charge more for electricity consumed at times of peak demand.
Mount solar panels to catch the sunlight from the west in the afternoon, and the panels’ production overall energy production would drop, but it would come at hours when the electricity was is often more valuable during these peak demand periods (often the big air conditioning surge in summer. read more about how to reduce electricity bills using aircon and solar).
Put simply, west-facing solar panels can often produce more power during afternoon peaks, better alleviating pressure on the network.
For example, in New South Wales the peak electricity price at 2pm is 0.3648/kWh, which is roughly more than double twice the standard or shoulder rate just before that time. So orientating your solar panels towards the West can be a Smart move.
Secondly, you need to understand when you use your energy. Just because you have to pay 0.48/kWh for energy bought from the grid between 2pm and 8pm, does not mean that they will pay anything like that for energy generated. In fact, if you export your excess solar electricity back to the grid at 3pm you are likely to receive only 0.06/kWh.
Hence you are highly motivated to generate your solar electricity when you are generally using energy. If you have a lot of energy consumption mid morning, you should orient some of your solar panels to east. If you have a constant amount of energy consumption during the day you might be best served by placing some panels facing east, some facing west, and even at different tilts to effectively flatten out your energy generation profile.
Basically the name of the game to minimise your energy bill is to give as little of your precious solar energy back to the grid as possible.
Maximising self-consumption will become an even more important in the years ahead should state governments continue the trend of lowering feed-in tariffs and increasing peak energy rates. it might even be a Smart idea to install batteries to store your energy rather than giving it back to the grid.
How do you know what solar system will be right for your home?
Firstly, make sure you get a few quotes from Clean Energy Council (CEC) Code of Conduct approved solar retailers. Secondly make sure they take into account your typical energy usage patterns. And best of all, pre-install an energy monitoring solution such as Solar Analytics that will allow your selected solar retailer to optimise your solar system, and you to make sure they deliver on their promise.
Why wouldn’t everyone point the panels west?
Some homeowners have panels facing north simply because that is the direction of the roof. Generally you will place the panels flush to your roof in an area that is mostly free from shade.
If either side of a roof is shaded by trees or buildings, you’d obviously choose the other side.
This might be east, north, west or anywhere in-between.
While some solar panel owners are paid time-of-use rates and are compensated by energy retailers in proportion to on the wholesale electric grid, many system owners cannot take advantage of the higher value of electricity at peak hours because they are paid a flat rate.
With the tumbling cost of batteries, it is likely that soon the best solution will be to simply cover the whole roof facing whatever direction, store what you need, and enjoys years of minimal energy bills.
How do I know what’s right for my home?
For solar energy system owners, the way to accurately track solar performance is through an active monitoring system.
These will pay for themselves in a short space of time., depending on the size and reliability of a solar energy system.
With the Solar Analytics Smart Monitor, you can view your energy usage, net electricity bought and sold, where and how you’re using electricity.
You can also see your system’s expected versus actual energy generated on a particular day and gauge if your solar panels are operating at optimal energy efficiency.
This helps you to identify if any solar system alterations or repairs are required.
What does this mean for solar systems already installed?
If you were one of the early movers who now enjoys the benefit of a fixed feed in tariff, then north facing at 30 degrees tilt is ideal to maximise your savings.
Changing the orientation of an existing solar panel is possible, however when the cost of having the array shifted is considered, it usually makes more financial sense to buy additional panels or battery storage.
Panels do not have to be pointed in just one static direction. A homeowner can buy a device called a tracker that will pivot the panels over the course of the day, like a sunflower, so they always face the sun.
A tracker can raise the output of a panel by 45 per cent. But installing trackers will cost thousands of dollars, require detailed structural engineering, and council approval. For residential houses, trackers rarely make financial sense.
A cheaper way to get the same number of kilowatt hours may be simply to buy a few extra panels and point them in different directions.
If you have solar panels pointing in different directions, it is important that each group of panels (called a string or sub-array) is connected to its own Maximum Power Point Tracker (MPPT) within the inverter, otherwise you will get poor performance from your solar system.
Alternatively you can use micro-inverters, which optimise every panel, however these are significantly more expensive than the standard wall mounted inverters.
If you already have a solar system and want to make sure it is performing as it should be, active monitoring is the best way to ensure your solar system is working optimally.
We are Australian Photovoltaic Engineers, Software Developers, Scientists, Solar Technicians and Designers, all passionate about sustainable energy and the power of solar.
Solar panel orientation
The placement and orientation of solar panels is just as important as which type of solar panel is used in a given situation. A solar panel will harness the most power when the Sun’s rays hit its surface perpendicularly. [2] Ensuring that solar panels face the correct direction and have an appropriate tilt will help ensure that they produce maximum energy as they are exposed to the highest intensity of sunlight for the greatest period of time. [3] Some solar arrays follow the Sun using solar tracking systems which significantly increase energy production. The following sections refer only to ‘fixed’ or non-tracking systems.
Direction
In the northern hemisphere, the general rule for solar panel placement is, solar panels should face true south (and in the southern, true north). Usually this is the best direction because solar panels will receive direct light throughout the day. However there is a difference between magnetic south and true south that must be considered. Magnetic south is the south shown when a compass is used, and this south points to the Earth’s south magnetic pole. Solar panels, however, need to face solar or geographic south, which is the direction towards the South Pole. [3] By the same reasoning, if the solar panel is located in the southern hemisphere, the panel should instead face in the direction of true north.
Depending on how solar panels are being used, it may also be beneficial to have a slight rotation away from due south. For example, depending on the use solar panels used for a home should face slightly south-west. These panels collect more energy when they face due south, but the energy is more useful if it comes later in the day. This turn allows the solar panels to produce more electricity at the hours when it is needed. Pointing the panels slightly south-west, in the direction of the setting Sun, would allow the panels to produce more energy in the evening, when people are home and using more appliances. The decrease in total production is balanced by the electricity available when it is needed most. In most areas there is enough electricity available from other sources in the morning and midday. [4]
When solar collectors are used for heating and lighting specifically. particularly in the form of fenestration such as Windows. it is actually best to have these collectors facing somewhat east. Warming the house for the day means morning sunlight is needed most. [5]
Angle
The angle or tilt of a solar panel is also an important consideration. The angle that a solar panel should be set at to produce the most energy in a given year is determined by the geographical latitude. A general rule for optimal annual energy production is to set the solar panel tilt angle equal to the geographical latitude. [6] For example, if the location of the solar array is at 50 o latitude, the optimal tilt angle is also 50 o. Essentially, the closer a solar panel is located to the equator the more the panel should be pointing straight up. The closer the panel is to the poles, the more they should tilt towards the equator. [3]
The angle of solar panels can also influence the power output due to climatic and environmental factors. In northern climates, snow accumulation on low-tilt panels can reduce or completely block the Sun’s rays from reaching the solar panel during the winter months. Although this effect will vary for every location, one study in Edmonton, Alberta, Canada concluded that the annual energy loss due to snow accumulation ranges from 1.6% at optimal tilt (53 o ) to 5.3% at low tilt (15 o ). [7] Additionally, low-tilt solar panels are more susceptible to soiling by dirt and debris which can also partially block the Sun’s rays.
For further reading
For further information please see the related pages below:
Which Direction Should Your Solar Panels Face?
As you can probably guess, solar panels generate more electricity when they are facing directly at the sun. While some utility-scale solar farms have structures that track the movement of the sun, residential and off-grid systems are generally left at the same orientation all year round.
In many cases, you won’t be able to choose which way you mount your panels, as you will be placing solar panels on an existing roof. In this case, it is important to understand how different orientations will affect the output of the panels.
If you have an off-grid or ground-mounted setup, you may be flexible in which way to face your panels. In this case, the ideal direction will depend on where you are located in the world, and what your goals are for your system.
This article will cover both these scenarios.
The orientation of your solar panels can be broken down into two types – Azimuth, and Tilt.
Azimuth
Azimuth refers to the compass direction your solar panels are facing.
In general, facing towards the equator (to the south in the northern hemisphere, and to the north in the southern hemisphere) will produce the most electricity over the course of a day, and should be your default choice where you have that option.
Note that when we say “south” what we are really talking about is geographic south (also called true south), not magnetic south. This means that if you align your panels to the south using a compass you will be slightly off the optimum azimuth.
To calculate geographic south you need to know the magnetic declination at your location which you can find using this website: https://www.ngdc.noaa.gov/geomag/calculators/magcalc.shtml
This website gives step by step instructions for finding true south:https://rimstar.org/renewnrg/finding_true_south_pole.htm
If you are installing a ground-mounted system, you are typically able to place the panels facing any direction you like, so you can just choose south (or north in the southern hemisphere). However, if you are placing solar panels on an existing rooftop you will have to work with what you have.
Can I install solar if I don’t have a south-facing roof?
Luckily for homeowners that don’t have south-facing roofs, you can still generate significant amounts of power from west and east-facing solar panels.
As an example, here are some simulated figures for a site in California. The table shows how much energy is produced per kilowatt of solar, per year, at different azimuths. The last column shows the percentage lost compared to 0° azimuth.
Loss compared to 0° azimuth
As you can see, even when facing directly west (90°), the system will still produce around 83% of a south-facing system.
(These are just some example numbers to give you an idea of how azimuth can affect output. These percentages will vary based on site location, and other factors such as tilt angle)
You need to be sure that you take losses due to azimuth into account when sizing your system. Therefore it is a good idea to use an online solar calculator to help you. Some of the typical hand calculation methods include rules of thumb for losses which assume a 0° azimuth.
Even though south-facing panels will produce the most energy over an entire day, there are some cases where it can be more financially beneficial to install your panels facing more towards the west. For example when your utility uses Time Of Use rates.
Time of use rates
Different utilities have different ways of charging their users for the electricity they use. Some just have a flat rate for every kWh of electricity used, while others use Time Of Use (TOU) rates.
TOU rates are when the utility charges you more for using electricity at peak times, than at off-peak times.
Since peak times are typically in the evening, it can make sense to generate more electricity from your solar panels later in the day, so that you are using less from the grid during these times.
This can be done by rotating your panels to the west, or if you have a rooftop with several different angles, it could mean you are better off placing panels on the west-facing rather than the east-facing sections.
When rotating your panels further to the west, you will generate slightly less electricity over an entire day. But since the value of the electricity you produce is higher, you may save more money, and therefore generate a better return on your investment.
Solar Panel Tilt
The other type of solar panel direction you need to consider is the tilt angle.
Tilt angle refers to the angle from the ground at which the solar panels are tilted, where 0° is lying flat.
During summer, the sun is high up in the sky so a low tilt angle would capture more sunlight. However, in winter, the sun is much lower in the sky so you would capture more sunlight with a higher tilt angle. Therefore the best tilt angle will be somewhere in between.
To generate the most electricity possible over the course of a year, a commonly used rule of thumb is to use the latitude of your location as the tilt angle. So for example, if you are located in Houston, Texas directly at 30° latitude, then you would tilt your panels at 30° for maximum electricity production.
While this method will give you a good starting point, close to the optimum tilt, it can often be improved on. You can usually increase your output slightly by decreasing the tilt to capture more energy during the longer summer days. How much you need to reduce the tilt depends on your location.
While some people use rules of thumb for this, we suggest simply trying a few different tilts close to your latitude angle, in whatever solar calculator you are using, and see which one results in the highest annual output for your location.
The increase in output that you get from this further optimization may be fairly negligible, but in some areas, it can increase output by around 0.5% or so, so it is worth checking.
Keep in mind that your racking installation may only be accurate to within 5° or so anyway, so you don’t need to get too caught up in finding the exact optimum tilt angle to within 1°.
If you are installing a rooftop system you will generally follow the slope of the roof, so you won’t be able to decide what tilt angle to use. Your system may produce a little less electricity than if it was at the optimum tilt, but it is unlikely to mean you can’t install solar at all.
For example, here are some simulated figures for a site in Los Angeles, California. The table shows how much energy is produced per kilowatt of solar, per year, at different tilt angles. The last column shows the percentage lost compared to the optimum tilt angle.