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Editor’s Note: This is the first post by Jessica Jones, Solar Consultant with Vista Solar Inc.

Three Key Questions for Your Solar Photovoltaic (PV) Installer

In the world of solar, there is a perfect storm developing. The current levels of government incentives, ever-rising electricity rates and declining equipment costs, have made purchasing a solar electric system more affordable than ever.  Consequently it comes as no surprise that consumer demand for solar is on the rise. No one questions that a growing market during a slow economy is a good thing, however, with the growing market comes opportunists attempting to enter the field without the expertise necessary to properly analyze their clients’ needs and provide quality solar solutions. Fortunately, you can identify and avoid most of the common blunders these folks are making by asking your installer a few key questions.

Question 1: How were my home’s particular features (shading, roof, fire codes) factored into the proposed system?

A professional installer needs to perform an in-person site evaluation to properly assess your home’s roof potential and sun exposure using a solar access measurement tool. Although web tools like Google Earth can help provide rough estimates, calculations based on these tools usually reflect optimal conditions rather than what is specific for your property. Satellite photographs don’t capture important details like how many layers of roofing materials exist on your home, which can affect the permitting process. If satellite pictures are not up to date, what looks like a shrub next to your home may actually be a tree that has grown into a sizable shading issue.

Although many homes have a large roof, not all of it is usable for solar. Roof orientation and obstructions like vents, chimneys, satellite dishes and vegetation limit how large a system you can install. Newly adopted  f fire guidelines also require particular areas of your roof be kept clear for safety.

It’s not uncommon for homeowners to sign on to a system design that doesn’t include these considerations, only to be surprised by avoidable change orders and significantly reduced incentives. Confirm that your installer’s system design addresses all of these factors so you can avoid such a situation.

Question 2: How will you connect the proposed solar system to my service panel?

You’ll want to ask this question for three reasons:

1. To ensure that the solar installer has actually examined your service panel

2. To understand if the installer plans to use a “line-side tap” or a direct busbar connection

3. To verify that the installer has designed a system that is compliant with the National Electric Code’s    “120% rule” (i.e. fits within the constraints of your existing service panel)

By not asking this question you open yourself up to the likely possibility that the installer will soon come calling with expensive change orders, or in the worst case, construct a system that cannot pass the final building inspection without costly upgrades.

It is critical that the installer examine your service panel prior to designing the solar system. Otherwise, there is no way for them to address issues 2 and 3 outlined above. Installers typically connect their solar systems to your service panel by connecting directly to the main busbar and protecting the connection with a properly rated breaker. In some instances, installers will use a “line-side tap” where the solar system is connected to the Utility side of the service panel, foregoing a circuit breaker. While a professional can perform a “line-side tap” safely, there are still many cities and counties that do not allow the practice. Your installer should verify that this is an accepted practice with your building department before using this design.

Finally, with a typical busbar connection, the National Electric Code allows a specified amount of energy to be supplied, or “backfed” into a service panel. The sum of the supply breakers feeding the busbar of a service panel can only add up to 120% of the busbar rating. This rule is intended to prevent potential overload conditions. If you apply the 120% rule to a 100Amp service panel, outfitted with a 100 Amp main breaker, you would only be able to add 20Amps worth of backfed breakers. Many inexperienced installers have proposed systems that would physically fit on the location’s rooftop but would far exceed the existing service panel’s allowable backfeed rating. The result is often an unexpected change order for a new service panel and a delay in the installation. Requiring an in-person site evaluation is the simplest way to ensure that your installer can properly address these issues.

Question 3: How did you calculate my expected rebates and tax incentives?

Lastly and perhaps most importantly, make sure your installer knows how to accurately calculate the government incentives that will offset the costs of your system. For instance, rebates for the California Solar Incentive (CSI) will automatically be reduced over time in 10 steps based on the total amount of solar systems installed. The step at the time of rebate submission determines the amount received. Your installer should know the current step.

Furthermore, ensure that your solar installer has based your rebate estimates on the actual shading and structural features, including the direction your system is facing, of the proposed location. They should be able to provide a printout of their data justifying the rebate value.

The federal tax credit is applied to the cost of the system after deducting the rebate amount. Confirm that your installer subtracted the cost of your rebate so you are not expecting an artificially high tax credit amount. Visit www.dsireusa.org for updated information about available incentives.

PV solar is an exciting and rewarding investment with short and long-term benefits. Make sure to ask your installer about shading issues, backfeed restrictions and government incentives to ensure that you are getting the best solar solution for an optimal return on your investment. Once your solar system is installed you’ll enjoy financial and environmental gains for years to come.

 

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