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Top 10 Items to Watch for in a Solar Proposal

Like any other major investment, purchasing a solar system involves a lot of research and education to make sure you get the best deal. When it comes to comparing competitive proposals, not all quotes are created equal. Here are a few major items you should check for as you try to narrow your list of potential installers.

  • 1. Is the module manufacturer and model defined?
It’s important to know the specifics of what equipment your installer will be supplying you. Although it can be difficult to trace exactly where a panel is made, make sure the manufacturer and model name are clearly identified on your proposal so you can verify that the panel maker is a reputable source. Keep in mind, the industry standard for a panel warranty is around 25 years. You will need to establish the likelihood that the manufacturer will be there to honor your warranty during that time.

We recommend your solar system to be sized anywhere between 50 – 80% of your historical energy usage. We do this by looking at your utility bill to see how many kilowatt hours you consumed in the past 12 months, then design your system to meet up to 80% of that. If you are being quoted a system that will cover 100% of your expected energy use, you might end up donating a lot of your solar energy to the utility!

Why do we aim for 80% offset? Why not 100%? There are two big reasons: the funkiness of the utility’s energy calendar and because we expect most homes to become more energy efficient over time.

The Funky Utility Calendar

Instead of using a normal January to December calendar, many NC utilities (including Duke Energy and Duke Energy Progress) use a calendar that starts in June and ends in May when they examine their customers’ solar energy production. This is important because with net metering you’re allowed to roll over excess solar production from month-to-month. So if you generate 1,000 kWh in January and use 800 kWh, you roll over 200 kWh as a credit for February. However, any excess that rolls over to the end of May is donated to the utility!

Unfortunately (and not coincidentally) the end of May is when North Carolinians need that production to roll over the most because they have to ramp up their energy usage to stay cool in the summer heat. In order to ensure that we don’t donate any valuable solar energy to the utility, we have to design our systems slightly smaller than we would if this funky limitation didn’t exist. So instead of 100% offset we normally hit around 80%.

Solar Production vs Home Energy Use Sample Graph

Improving Home Efficiency

The second reason we design up to 80% is that a majority of the time homes are getting more efficient. Between new appliances, upgrading light bulbs from incandescent to CFL and LEDs, changing out the windows, or eventually replacing the HVAC system, home efficiency is continually improving. If a system is designed to meet 100% of the home’s energy use in its current condition, it would again be overproducing once something like the old HVAC is replaced with a new and more efficient unit. 

Like all good rules, the 80% guideline has exceptions! Adding a pool, hot tub, electric vehicle, or even another family member mean more energy consumption for the homeowner. We can upsize (or downsize) a system when we know the homeowner’s energy needs will be changing in the near future. Similarly, we will also gladly design a system to meet a homeowner’s goal of going net zero!

  • 3. Will a central string inverter or micro inverters be used?

The inverter is the brains of your solar system so make sure you’re getting a smart, reliable brain. There are two main types of inverter: string and micro. String inverters are centralized and all of your solar panels will feed to one inverter (or two for larger systems!). With micro-inverters, each solar panel will have its own inverter installed on the back of the panels.

We highly recommend string inverters for two reasons. First, the advantage that micro-inverters had in dealing with shading has been erased in recent years by advances in string inverter technology. Secondly, in our experience micro-inverters don’t hold up well to NC’s heat and humidity and are more likely to fail and/or need maintenance than string inverters.

  • 4. Has a solar professional visited your home to complete an onsite assessment prior to the proposal?

It’s difficult to estimate exactly how a solar system will perform in a given location without a solar professional coming out to your home. While satellite imagery is advancing, key elements that can easily be spotted in person are often missed online. Things like a dormer, chimney, vent, or tree shading can be misleading on a digital 3-D rendering. Many times, satellite images are also outdated, so there’s a good possibility those tiny trees in your backyard are now a big shade factor for solar.

  • 5. Does the production range of your system fall within the NC standard of 1200 kWh to 1450 kWh per kilowatt annually?

Make sure your solar production estimate doesn’t have any fluff! Looking at the ratio of kilowatt hours (kWh) to kilowatts (kW) of solar installed is a great way to compare production estimates across multiple solar quotes. Our rule of thumb is that a solar system in North Carolina should produce around 1,300 kWh per kW each year — e.g. we’d expect a 5 kW solar system to produce 6,500 kWh per year. For the perfect solar system in North Carolina — facing due South, tilted to 35 degrees, and no shading — the maximum production we’d expect to see is 1,450 kWh per kW annually. 

If one of your solar quotes shows higher production values than 1,450 kWh per kW it should raise a red flag that maybe that solar company has added some “fluff” to the numbers to make their quote look better. We always confirm our solar production estimates with a physical in-person site assessment in order to take accurate orientation, tilt, and shading measurements that give us the confidence to guarantee our customers’ production!

Gif of a fluffy puppy being cute
When it comes to solar, leave the fluff to the pups!
  • 6. Does the solar installer guarantee their solar production estimates?

This is a major question you should be asking each company that offers you a solar proposal. Your biggest risk in going solar is that the system doesn’t perform as it was designed and sold to. We firmly believe that the homeowner should not be liable for the risk that their system was advertised to produce more than what is physically possible given their roof, shading, and location.

As a solar installer, we back our production estimates with a performance guarantee. We’re only able to do this because we go to each home for a site evaluation beforehand, which allows us to determine how the shading, roof pitch, and location of the home will impact the system’s production. Unfortunately this isn’t an industry standard yet, but we hope other installers will get on board!

  • 7. Are both production and consumption monitoring included in the standard install?

Most solar installers offer complementary monitoring for the system once it’s installed. The biggest distinguishing factor to narrow the competition will be what levels of monitoring are included – production only or production and consumption.

It’s obviously cheaper to just offer production monitoring so you can see how much energy the system is generating. Our approach is different though, and stems from our mission to change the way people make and use energy. By offering both production and consumption monitoring, our customers can see their energy usage and adjust their habits to save even more money. We believe production and consumption monitoring should be the standard, and we’re pushing the industry that way, but we’re still one of the few companies who include both without an up-charge.

  • 8. Is their information about your utility accurate? How are they estimating the increase in energy prices in the future?

To project the lifetime solar savings potential for your system, the installer must know your current energy rate. If this number is wrong, the accuracy of their estimate of the financial benefit of the system will be off from the beginning. We have also seen some installers grossly overestimate how the cost of energy will rise in the future to make the solar system look more profitable.The Federal Energy Information Agency estimates a national average electricity price escalation rate around 2% annually. NC’s electricity prices are currently below the national average, so we forecast the escalation rate slightly higher around 3%. Make sure the current electricity price and price escalation rate are clearly referenced on any solar quote your considering!

sample graph of lifetime solar savings
  • 9. Is the pricing transparent with terms clearly listed?

Beware of markup to markdown tactics and sudden special discounts. If an installer is able to give you a flash teacher discount or other [fill in your career] discount it’s very likely that their system was overpriced to begin with. And no, the rebate isn’t ending tomorrow, so while it is important to act quickly to secure your spot, you shouldn’t feel pressured by your installer to sign immediately.

As with any other major investment, it’s always important to make sure the turnkey price is black and white, and all items are clearly defined. If you’re financing your system, make sure the total system price is listed along with the monthly payments. We’ve seen a lot of new players in the NC solar market recently, who don’t understand NC specific solar policies. It never hurts to double check that the rebate and tax credit the installer has quoted are accurate.

  • 10. Does the proposal clearly outline the warranties included with your system? Will the company be around to support you in 15+ years?

For the most part, manufacturer warranties for panels and inverters are pretty standard across the industry. This is what is typically covered by the manufacturers we work with:

  • 25 year power warranty covering panel production
  • 10 year product warranty covering aesthetic damage
  • 12 year inverter warranty

We also provide a labor warranty to match the manufacturer’s warranty. But above all else, the most important factor to consider is whether the solar installer you choose will be there for you when you need support later on. This is a great time to pause and take a moment to reevaluate how long the installer has been in the solar industry, how long they have been established in North Carolina, and how long they will continue to be here.

Key Takeaways

Production, warranties, modules, inverters — there’s a lot to consider when purchasing your solar system! 

Here are the key takeaways:

  • Make sure the product specifications, services, warranties, and prices are transparent and clearly defined
  • Have the installer visit your home to do a solar assessment before selling you a system
  • Evaluate your current and future energy needs, talk with your installer to make sure the system is not oversized
  • Review whether the installer is established in the NC solar industry and understands local policies and procedures
  • Determine if their company history indicates whether they will be here for the long run
  • Don’t hesitate to collect several quotes for comparison, with some from local installers
Home of an SEM customer with "I'm Going Solar" sign

Don’t hesitate to reach out if you have any questions, we’d be happy to help support you on your solar journey!

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