How to install solar panels on a roof

The roof is the most preferable place to put your solar panels – after all, usually it doesn't serve for much else. In situations when a roof isn't an option, you can put your panels on the ground. This way of installation has its disadvantages: they get dirty quicker, they occupy space in your yard and oftentimes they are more affected by shadows of trees, bushes or buildings than those that are installed on the roof. Attaching solar panels to walls is also an option, but it results in higher costs of installation and lesser efficiency.

Before installing solar panels, you have to make sure that your roof will be able to withstand their weight. An average weight of a monocrystalline or polycrystalline panel is around 2.5-2.7 pounds per square feet. Most of the time solar panels do not pose any threats to the roof, but to be absolutely sure and safe, it might be a good idea to invite a specialised engineer for a proper examination, especially if you are living in an old house. Even if an expert won't be satisfied with the condition of the roof, you will be able to add additional support. Keep in mind, that if you ever consider replacing the roof, you would have to remove installed panels — and they are meant to last for 25 years or more. If your roof is flat, it's better to clean up before the installation: get rid of any litter or vegetation.

Generally, solar panels are installed on the roof with the help of mounts that get attached to the roof by stanchions, giant screws. The easiest solution is to attach them to rafters of your roof, which you can find with the help of its blueprints.

There have to be at least four feet between two stanchions. After you've drilled holes, you can put screws and secure them with an impact driver, if you have one. Don't forget to seal the screws, so that there is no heat loss occurring through holes you've just made — for this purpose thermoseal roofing is the best option.

Installation of solar panels is a process that you better perform right — there rarely is a second time for it. Try to get everything right for the first time: the length and width of mounts have to be double checked. To make sure that side rails that you've just installed are parallel, compare the diagonals: measure the distance between top of one rail and bottom of the other, then switch and compare. If measurements are the same, then rails are parallel. If they are not, make necessary adjustments. After that you can install the middle rail. Don't forget to check their alignment afterwards.

After that you can either mount solar panels or attach wires to them first — the order depends on the situation. The wire from the solar panel goes to a solar inverter kit that should be placed underneath a panel (you'd need 6-gauge copper grounding wire for inverters). Once the whole system on the roof is interconnected, wires can be plugged into the electrical meter and sub-panel. And there you have it: your own home solar panel system.

While installing solar panels on a roof isn't rocket science, it is still a time-consuming and dangerous task that requires accuracy and precision. The best option is to hire a professional crew that can help with installation. If you are determined to do everything yourself, make sure you are safe — don't damage yourself, the roof or the panels.

There are however types of roofs where drilling is not the best option — tile roofs and metal roofs. Metal roofs with standing seams are the most convenient for installing solar panels. No special preparation needed — modules are attached to the roof with U-clamps. Not only is it super simple, it also allows the air to circulate under the panels. It contributes to the cooling of the system, raising the efficiency of solar panels.

Tile roofs are a much more problematic example. There are a couple ways to attach solar panels to such a roof. First, you can add a special rack that goes on top of your roof and will act as a framework for panels. As the second option, you can remove some of the tiles and replace them with metal shingles and then you can use screws or clamps. The worst case scenario is probably the Spanish roof, because it is very hard to install a solar panels system there without breaking any tiles. When ordering the install of solar panels on a tile roof, make sure that the company pays for any tiles that were broken in the process.

Another type of roof that requires a specific approach are corrugated metal roofs. U-clamps don't work there but there are specific brackets on the market. They are designed to fit on the rib and then they are attached by galvanized screws.

Flat roofs are an interesting case. From one perspective, they allow for panels to be turned to any preferable side and it's possible to customize the angle with the help of mounts, whereas with pitched roofs you're given the side, and an angle might be hard to adjust. No drilling is required — on a flat roof solar panels can be fixed with the help of, for example, cinder blocks.

On the other hand, not every company issues a warranty for panels that are installed on a flat roof, and what is more, not every brand performs an installation on a flat roof. If you've decided to use screws for fixing panels, the risk of leaks is higher than in the case of a normal roof, because water doesn't slide off the roof without the tilt. If you've decided against mounts that help to fix the angle, rain can't wash panels because there is no incline, so they get dirty much more quickly. Besides, if panels are placed flat, they get less sunlight over the day, which results in lesser amount of energy produced (the only exception are the roofs on the equator, where panels are supposed to be placed flat).

If you're wondering should you worry about your solar panels in cases of extreme weather conditions, the answer is "no" — of course, up to a certain point. Every model of solar panels gets tested in STC (Standard Test Conditions). Not only its performance gets measured, a module is also tested to withstand extreme hails and harsh winds. Panels should be fine with the wind even at speeds of 100-120 mph if installed properly and modules can also withstand a hail at a speed from 20-30 m/s. If anything, solar panels even extend the lifespan of your roof by protecting it from water. Generally, rain takes care of washing solar panels but it is still recommended to perform cleaning of your panels once a year or their efficiency might drop overtime. If you want to know more about lifespan of solar panels and warranties, check out our article "How long do solar panels last? In a nutshell, quite a while"