Part 3 of my Residential Solar Power series is Choosing a Solar Power Contractor. Here are some questions to ask before hiring a solar power contractor to install solar panels on your roof.
Solar panel installation is mostly simple (read about Solar Power Basics). There are established guidelines that most contractors follow, depending on the direction of the panels, the roof’s pitch, and other factors. If the solar array is installed properly, there should be little variance in energy efficiency from one company to another.
Solar panel installation requires more roofing expertise, than electrical expertise.
Another important aspect of solar panel installation is the direction. It’s best to find a location with very little shading. The best direction for solar panels to face is south, then west, then east, then north.
Roof Installation Matters
Solar panel installation requires many holes to be drilled into your roof. If the installation is not done properly, there can be leaks and water damage. Most of my questions check the roofing expertise of your solar power contractor.
Consider this basic roofing principle: You need flashing around every object on your roof to direct the water away from it. This includes vent pipes, and solar panel footings. Anything that is installed on your roof needs flashing. Without the flashing, water can easily leak into your attic and home. On a tile roof, two flashings are required: one on the paper underlayment, and another above the tiles.
What Attaches to Your Roof
There are three important solar system components, that attach directly to your roof:
- Footing (drilled into the roof)
- Flashing (covers and surrounds anything connected to your roof)
- Sealant (seals the flashing to the roofing, to prevent water penetration)
When you install a solar panel system on your roof, many holes are drilled into the roof to secure the footings. For example, if you purchase a 5 kW system, you will install approximately 15 panels to your roof, and drill in approximately 30 different places. This means 30 places that need footings, flashings, and sealant to be correctly installed, to avoid potential roof leaks.
Don’t Forget the Flashings!
Not all solar installers correctly install flashings when they install solar panels. I have seen a solar power contractor’s website that showcases an example of a solar installation – with NO flashings. None.
While a building inspector will approve the solar system installation upon completion, inspectors often do not go onto the roof to inspect. Don’t count on the building inspector to identify missing or improperly installed flashings.
Another basic roofing principle: Everything on your roof must be able to withstand the elements. It’s important that all the materials on your roof are designed for years of exposure to sun, wind, and rain.
Questions to Ask Your Solar Power Contractor
Many solar salespeople don’t know much about installation. You may need to ask to talk to someone who is directly responsible for the installation. If a solar company doesn’t let you speak with someone regarding installation, you may want to cross it off your list.
1. What is the manufacturer of the solar panels and the inverter?
There are many different solar panel and inverter manufacturers. Choose one that has been in business for at least 15-20 years. SolarWorld, for example, is made in the USA and has been in business for over 40 years.
2. What type of flashing will you use on my roof?
Good Answer: A galvanized metal flashing with at least 6″ of flashing all around the cone (the part that goes around anything protruding from your roof). If it’s a tile roof, there also needs to be another flashing at the tile that goes at least 8″ around the cone.
If you live near the ocean, you should use copper flashing instead. When you get ocean fog regularly, there’s a lot of salt in the air. Normal galvanized metal flashing will oxidize.
3. What type of mounting hardware/footings will you use to install the solar panels to my roof?
The mounting hardware is a crucial part of your solar panel array – it’s attached directly to your roof. This is where you need to make sure that your roof will not be compromised, and will not have holes that aren’t flashed properly.
Good Answer: At least a 3/8″ x 3 1/2″ lag bolt to mount the footing to the roof. And then the standoff (connecting footing to panels) should be at least 3/4″ wide for structural support and at least 6″ above the finished roof.
Bad Answer: TileTrac or Tile Hook. You can’t possibly put an effective flashing on these footings.
3. What kind of rail system to you use to connect the footings to the solar panel?
Good Answer: U-channel rail system. The U-shape creates a space to hide the wires, and protect them from the elements.
Bad Answer: UniRac rail system. This system does not offer a space to hide and protect the wires. The solar power contractor needs to zip-tie the wires to the rails, which exposes them to the elements. This can lead to premature wear and failure.
4. What do you use to seal the flashing to the roofing?
Good Answers: Volcom or Polyurethane Caulk. These substances can withstand the sun and wind.
Bad Answers: Mastic (plastic roof cement), Latex, or Silicone. Silicone is required for the junction box, but should NOT be used anywhere else. These substances break down over time, with exposure to sun, wind, and rain.
5. Do you replace any broken roof tiles?
Your solar power contractor should lift some tiles ahead of time, and bring extras to the job in case of breakage.
6. What kind of conduit do you use?
Conduit is tubing, or pipe, encases the wires that connect the solar panel array to the inverter and your electrical box. All conduit needs to be elevated on all types of roofs, except for barreled clay tile roofing.
Good answer: EMT, or Electrical Metallic Tubing. Metal is highly durable and withstands the elements.
Bad answer: PVC, or Polyvinyl Chloride. Plastic sags over time.
A related question is, Do you paint the exposed conduit? The answer should be YES. If you paint the conduit, it will last longer.
7. What do you use for blocking to elevate the conduit?
The conduit should NEVER touch the roof. It needs to be above, on blocking.
Good answer: composite decking. Lifespan 25+ years.
Bad answer: pressure-treated 2×4. Lifespan only 10-15 years.
8. Where will you install the conduit?
Whenever possible, the conduit should be hidden, installed through the attic. It is usually not necessary to have conduit running along exterior walls.
9. Where will you install the inverter?
If there is one central inverter, the best location for installation is in a cool, dry location, preferably the garage.
10. Are the solar panels above the roof, or do they go directly on the roof?
Solar panels should be at least 6″ off the roof, whenever possible. This helps them stay cooler. When flat against the roof, the solar panels become too hot, which affects power production.
11. Where will you install the AC disconnect?
The AC disconnect is a way to shut off your system in an emergency, such as a fire. It needs to be outside, by the electrical meter. SDG&E requires a plaque installed by the meter that indicates the location of the AC disconnect.
12. Do you put a DC disconnect at the array?
There is no way to turn off a solar panel unless you have a DC disconnect. This is a safety issue if someone needs to work on them. You can bolt an DC disconnect (costs about $6) to the rail at the array.
13. Once the system is in, will you clean the panels or provide other annual maintenance?
While cleaning the panels may not be necessary in San Diego, your solar power contractor should come out every year to inspect the system, and make sure no footings have come loose.
14. What type of warranties come with the solar system?
All solar systems should come with at least a 10-year manufacturer performance warranty to protect against degradation of more than 15% from their originally rated electrical output. You may also have the option to extend your warranty later. For example, a 10-year extended warranty for an inverter may cost $400. On the other hand, purchasing a new inverter can cost $2,000.
Your solar power contractor should offer a minimum 10-year installation warranty. This installation warranty should cover repair and replacement of the system. In addition, it should cover any expenses not otherwise covered by the manufacturer. Some solar power contractors offer a 25-year warranty.
15. What should I look for on the solar installation contract?
Your solar installation contract should include the following eight items:
- The installer information – name, license number (see below for how to check license status), contact information.
- System size (Read Solar Power Basics to help determine your system size)
- Make/model/quantity of solar panels and inverter(s)
- Warranty language
- Work schedule description – usually 2-3 days total
- Price/payment schedule
- Clear description of all system components
- Down payment requirement – limited to $1,000 or 10% of the total project, whichever is less.
Where to Find a Solar Power Contractor
Here are two websites that can help you choose a solar power contractor:
- https://www.californiasolarstatistics.ca.gov/search/contractor/
- https://www.sdgehomeupgrade.com/home-owners/find-a-contractor
In addition, ALWAYS check a contractor’s license status with the California Contractors State License Board. For example, solar power contractors must have at least one of the following license classifications:
- A – General Engineering Contractor
- B – General Building Contractor
- C10 – Electrical Contractor
- C46 – Solar Contractor
Federal Tax Incentive (through 2034)
While prices of solar power systems vary, the federal tax incentive is the same, no matter what company you choose. Federal tax code allows for a one-time 30% Residential Clean Energy Property Credit to purchase home solar photovoltaic systems.
Currently, the 30% Residential Clean Energy Property Credit is available through 2032. It then falls to 26% for 2033, and then 22% for 2034. Finally, the credit will expire after 2034.
Continue Reading
Residential Solar Power series, Part 1 of 3: Solar Power Basics – How solar power systems work, different options to choose from, costs and incentives, and the benefits of buying vs. leasing a solar power system.
Residential Solar Power series, Part 2 of 3: What to Do Before You Buy a Solar Power System – How to make your home energy efficient, and how to decide how much solar system to buy.
7 Ways to Finance Green Upgrades – so many ways to pay for solar!
Selling with Solar – things to consider if you’re planning on selling your home with financed solar.
Solar Planning for Electric Vehicles – how much solar will you need to power your EV?
Special thanks to Mark for helping me with this article series:
Mark M. Pulis is the owner of Residential Raters LLC, an energy efficiency firm for homes and small buildings. Mark provides consultations regarding HVAC systems, solar panel installations, energy consumption, energy efficient mortgages, and more. He is a certified Home Energy Rating System (HERS) rater by California Home Efficiency Rating Services. He is also certified by the Building Performance Institute (BPI) as a Building Analyst and Envelope Specialist. Finally, Mark can help you plan and choose the right solar system for your home. Contact him at (858) 869-9412 or via his website.
