Site Survey for PV Installation

One of, if not the, most exciting portions of the overall system installation process is the site survey. Why? Because you get to work with a blank slate (after all, the client shouldn’t have another PV system anywhere on his building or property) and create a PV system from the ground (or roof) up.

As the person who performs the site survey, you need to be able to identify any potential trouble spots and the best ways to address the issues they pose from the beginning of the project.  

The site survey is generally your one chance to obtain all the required information about the site to create a proposal that works for both you and the client. It’s also the only time you can really work with your client to establish his goals and expectations for his PV system before you’re too far along in the process. I explain the steps and methods you need for a site survey in this article. I also give you an idea of what to do with all the data that you gather. 

Setting the Stage for a Site Survey

When you’re at a client’s house or business to perform a site survey, you must be diligent about collecting the information you need. You don’t want to leave out any information that may prove critical for you to provide an estimate and a quality design for your installation crew.

Return trips to gather information that should’ve been collected the first time around do nothing but waste your time and risk making you look less than professional. In this section, I provide some pointers on how to prepare for a site survey. 

Putting aside enough time  

You can’t conduct a solid site survey without allowing yourself ample time and staying focused (a site-survey form can help focus your itinerary; see the next section). I suggest allocating at least an hour of on-site time. If through preliminary phone or inperson conversations with the client you get a feeling that he’ll require extra time, then schedule yourself enough time to answer his questions while leaving enough time to collect the information you need. 

Speaking of questions, the one you’ll hear most often (aside from “What’s the average cost?”) is “How much money will this save me each year?” Although this can be a difficult question to answer without knowing a number of specifics, you should have an answer for it. 

Use the PV Watts tool to become familiar with what a 1 kW PV array can produce in the client’s area. (Figuring out what a 1 kW system can produce means you can easily do the math to adjust the values for your client’s site.) This free tool, found at, takes information from you and applies weather information from collected data and returns estimated energy values for a PV system.

One of the best features of this tool is the ability to vary input factors such as the direction you want your array to point or what tilt angle you want it to have. With just a few mouse clicks, you can run some scenarios and be able to determine the best solution for your site. (Note: If you’re new to PV Watts, I suggest using Version 1 first and then moving on to Version 2 as you become more proficient with the tool.) 

By taking the time before the site survey to acquire this information, you can give your client an estimate for the array size and the amount of money the system can save him each year after you complete the site survey. Just be sure to give the disclaimer that you won’t know the exact size of the array or how much energy it’ll produce until the design is done. 

Creating a standard site-survey form

So that you don’t forget any of the information you need to acquire while conducting a site survey, seriously consider carrying a standard site-survey form. Using a standardized site-survey form keeps you on track by reminding you what to collect and giving you a place to write all of that down.

It also improves the quality of information you walk away with and can save you time when a client whom you gave a bid to a year ago suddenly calls and says that he’s ready to buy. With all the necessary information recorded on your site-survey form, you can save yourself another trip out to the site.   

A good site-survey form can be easily replicated by others within your organization, meaning no matter who’s conducting the site survey, the re

quired information will be obtained and recorded. In a program such as Microsoft Word, you can quickly create a site-survey form that contains places for the following information:

  • The site address and client’s contact information (e-mail and phone num- ber)
  • The type of system desired (grid-direct; utility-interactive, battery-based; or stand-alone, battery-based)
  • The utility company (along with contact information if you’re not familiar with the local utility)
  • The information from the client’s main distribution panel (see the later “Collecting Basic Information during a Site Survey” section for the how-to on obtaining this data)
  • Space for notes on the proposed inverter location
  • A note section for options for wiring the array to the inverter
  • The roof tilt and azimuth if the array will be roof mounted or the estimated array tilt and azimuth if the array will be ground mounted Information on the type of roofing material and its condition
  • A note section for any issues with the structure
  • A list of pictures to take
  • Space for notes about the customer’s requests or special site considerations 

Toting a site-survey bag

When you go to do site surveys, you’ll be climbing on roofs, traipsing through fields, and walking through all sorts of buildings — all while carrying the tools you need to complete the survey. For these reasons, I can’t stress how essential a dedicated site-survey bag is. 

I prefer a tool bag with multiple pockets and a heavy-duty strap so you can carry the bag over your shoulder. The strap is key because you’ll be carrying the bag up and down ladders and in and out of access hatches.    The following tools should always be in your site-survey bag:

  • A good-quality digital camera (see the next section for tips on using this tool during a site survey)
  • Measuring tapes, including a • 25- or 30-foot tape • 100-foot tape
  • Wheel tape (this one’s critical for commercial applications)
  • A compass An angle finder (see the later “The tilt angle” section for the scoop on this tool)
  • A calculator
  • A clipboard and notebook with pens and pencils
  • A flashlight and extra batteries (note that a headlight works great in attics while allowing you to keep your hands free)
  • A shading-analysis tool (I describe several of these tools later in this article)
  • Screwdrivers (you can get away with just one if you have a 10-in-1 screw- driver)
  • A digital multimeter
  • Tinted safety glasses   
  • Although a ladder won’t live in your bag, make sure you have it on hand. Very few site surveys can be completed without accessing a roof or attic.

Picture This: Documenting Your Entire Site Survey with Digital Photos

One of the best pieces of advice I ever received regarding site surveys was to take enough of the right photos so I could recreate the site when I got back to the office. A good-quality digital camera is therefore an essential tool for any site-survey bag.  If you’re in the market to buy a new digital camera, do a little research first. I sug- gest looking for a camera that can sustain some abuse (like being dropped and/or being exposed to water).

Simple point-and-shoot cameras are sturdier (for your purposes, anyway) than the fancy digital SLRs out there, plus you can get high-enough-quality pictures from them. Compare different models within your price range using the solid reviews found at    Chances are you’ll find yourself doing multiple site visits in a day, so before you do anything else during a site visit, take a photograph of the front of the building. Doing so helps you establish the location of all the pictures that follow. Without establishing your location in the beginning, you can easily jumble all of your pictures together.

To help yourself make sense later on of the photos you take, be consistent with your procedures. By keeping a consistent order to your site survey, you’ll be more likely to remember the information needed at each step. I personally like to start at the PV array location and follow my way through the rest of the system, but I also know some installers who like to work in the opposite direction. Find the method that makes sense to you and stick with it.  Here are some tips for taking photos during your site survey:

When you’re looking at mounting the PV array on a roof or on the ground, take multiple pictures from each corner of the array location so you can see potential issues from each vantage point during the design process.

Use reminders as to where you’re taking the pictures from. For example, if you’re planning to use a satellite image or a roof plan for recording measurements, then take a picture of the image/plan you’re using while pointing at the location you’re at. So if you’re on the southwest corner of the roof, take a picture of the roof plan while you point at the southwest corner of the roof. Then take the pictures from that vantage point.

You can do the same thing if the array will be mounted on the ground; just follow the same process to fully document the site. Repeat these steps for every location where any PV equipment will be installed. I recommend identifying alternate equipment locations too. After all, you never know whether the location you covet for the inverter is really reserved for some prize-winning rose bushes.   

Another trick is to use the video feature of your digital camera and record the same vantage point you just photographed. Doing so gives you the ability to talk to the camera and remind yourself of certain points or give co-workers some insight into factors or considerations worth noting. 

Collecting Basic Information during a Site Survey

You need to gather certain pieces of information during each and every site visit; you also need to look out for oddball things that may cause problems later. In the sections that follow, I look at the most basic (yet critical) pieces of information you need to acquire.    When performing a site survey, gathering the information is vital, but so is maintaining your safety. Any time you’re climbing on roofs, walking through attics, or opening electrical boxes, you’re doing real work.

All of these activities have inherent dangers that you need to think through. If during your site survey you find yourself in a situation that feels unsafe or makes you uncomfortable, immediately stop what you’re doing and find a different way to perform the task.

General site information

When you show up to perform a site survey, it’s easy to get so focused on all the little details you need to document that you forget to look at the big picture. Yet taking an objective look around and asking a few questions can save you from wasting your time.

Following are four tidbits of general site information you should find out before you start delving into minutiae:

1. What’s the shading like at the proposed location? I explain how to perform a basic shading analysis later in this article, but you also need to account for the other shading-related site conditions that may cause problems. The one that catches people the most is future shading — objects that aren’t there now but may shade the array in the future.

For instance, those small trees on the south side of the building won’t always be small, and the empty land to the south of the property may one day be the home of several tall buildings.   If the view from your client’s site is clear now, you may be able to protect it from any potential shading issues.

Many areas throughout the United States have solar-access laws that allow a person to protect his solar resource from shading sources on adjacent properties. These laws are typically enforced at the municipal level, so check with the local building department to see whether solar-access laws apply in your client’s region.

2. Are there any restrictions for the site? Such restrictions can include but aren’t limited to homeowners’ associations, city covenants, and historic districts.   At the very least, your client should know whether he belongs to a homeowners’ association; you can then ask the association’s contact person about any association restrictions. The local building department can provide you with any other special requirements that are in place based on the building’s location.

3. What agencies need to give approval for the installation? You absolutely need to know what (if any) restrictions are in place due to local specialty codes and firefighter access. The best place to find out what’s required for agency approval is the local building department (the same office that issues permits). You also need to check in with the local utility to make sure you meet its requirements.

4. What’s your client’s target budget? You can easily establish a rough estimate of the PV system’s cost based on your equipment choices and the installation specifics, but you need to know what your client’s financial thresholds are.

For example, if there are substantial unforeseen issues, how much money is the client willing to spend to fix an underlying problem before moving on? 

Structural and mechanical information

How much physical space is available for the installation? Typically, PV systems are installed on the roofs of buildings or on free land space. Your task during the site survey is to make sure the space available will suffice for the client’s desired PV system. Your client may have an idea of where he wants the array to go, but it’s your job to make sure a better alternative doesn’t exist.   

The area you have your eyes on may be the same as someone else. Always verify that other plans don’t exist for the space you want to use, such as plans for solar thermal collectors or skylights.  Here are some additional structural and mechanical questions that you should ask if the array will likely be mounted to a roof:

What are the dimensions and shape of the roof area available?

Taking the dimensions of the roof area you plan to install on will help you sketch out the roof later when you’re ready to plan how the array will be arranged on the roof (later in this article, I give you tips on how to use satellite photos and three-dimensional drawing programs to help keep this sketch accurate).

During the site-survey process, you also need to identify obstructions (such as plumbing vents, chimneys, and attic vents) on the roof as well as their locations.

What condition is the roof material in, and how old is the roof covering?

Placing an array on a roof that will need to be replaced in a few years doesn’t make a lot of sense. If a reroof is in order, suggest it be done now and be sure to work closely with the client and the roofer to coordinate phases of the project so you can continue with the PV system design and installation in a timely fashion.  

A possibility for dealing with a reroof and keeping your project moving is to do some of the rack installation before the roofers come in and allow them to seal the roof attachments.

What’s the roof framing like?

The roof’s framing plays an important role. Most modern homes and commercial buildings (those built since the mid-1970s) tend to have roof framing that’s adequate for a PV array mounted parallel to the roof so long as a single layer of lightweight roofing material (such as composition asphalt shingles or wood shake) is used as the roof covering. Why? Because the roofs of modern homes are designed to handle multiple lightweight roof layers. As long as only one layer is present, adding the weight of a PV array will be less than the structure’s limitations.

If the building was constructed before the mid-1970s, plan to spend a few hundred dollars to have a structural engineer evaluate the roof for you and outline any changes you need to make to safely support the array. Make sure this consultation happens as early as possible in the system design process.

Note: Many commercial buildings are built with the minimum requirements; therefore, they may not be able to support a roof-mounted PV array of any size.

What are the dimensions and spacing of the roof framing?

Most residential roofs have rafters or trusses that are made of dimensional lumber that’s either 2-x-4 or 2-x-6 and are spaced 2 feet apart, which gives you a relatively narrow space to hit for your array’s attachment points. For commercial roofs, the structures vary greatly. Some buildings have lumber, similar to residential roofs; others use very large wood support members; and some use steel supports.

Consequently, you should take the time to verify the roof structure in order to properly attach the array in any system that’s being installed on a commercial roof.   Always do your best to verify the roof framing composition and orien- tation when conducting your site survey.

Be sure to carefully evaluate rafters that are overspanned — a situation where the rafter has too much space between vertical support members. Different spans are allowed based on lumber type and roof-loading restrictions, but as a general rule, if the rafters have a span of more than 7 feet between supports, you should investigate the need for adding support by consulting a structural engineer.

After roofs, ground mounts are the most popular type of racking system. Unless your client’s site has unusually loose soil (like sand), you can work with a racking company (and maybe an engineer, if necessary) to determine the best possible mounting solution for the array. Of course, before you start talking to a racking company, you need to make sure the location is suitable for mounting an array.

Electrical information

If you’re installing a stand-alone, battery-based system, you don’t really need to worry about examining the existing electrical service and equipment because the stand-alone system will be providing all the energy for the client moving forward.

For utility-interactive systems (whether grid-direct or battery-based), you have a number of items to review while you’re on-site because you’ll eventually connect the PV system to the utility:

What are the specifications for the main distribution panel (MDP) and the main circuit breaker protecting the panel?

The ratings on the MDP and the main circuit breaker play a major role in determining a PV system’s maximum size. When looking at the existing electrical service, you need to document the specifics on the MDP and any subpanels you want or need to use, including their physical locations. The voltage for most electrical services in residential applications is 240 VAC at various current levels; for commercial applications, the voltage is usually 208 VAC or 480 VAC. Busbars are the pieces of metal in the back of the MDP that connect the circuit breakers in the panel to the wires coming from the utility (you can’t see them when the cover of the MDP is on).

Every MDP has a rating for its bus-bars on the label attached to the inside of its cover. This rating is a value for the amount of current that can flow on the busbars inside the panel without causing any problems.

Standard residential MDPs have either a 200 A or 225 A busbar rating and may simply be labeled 200 A Max (or 225 A Max); commercial busbars typically start at 200 A for small facilities and can exceed 1,200 A in large facilities, with a number of options in between.

The other specification for the MDP (and any subpanel used) is the rating of the main circuit breaker protecting the panel. For the MDP, this is often the same size as the busbar rating. The ratings for circuit breakers in subpanels vary based on the loads located in the subpanels.

Are there any open breaker spaces on the main electrical panel?

Look in the MDP or subpanels to check for available space to put a breaker. Then connect the inverter’s output wires to one of these panels by placing a breaker in the panel and wiring the inverter to it. (This process is similar to putting a breaker in the panel for a new set of outlets or a new load except that the electrons are running in the opposite direction.) If the panel is full, you need to either make room or replace the existing panel with a larger panel.

Where will the inverter and required disconnects be located?

Determining a location for the inverter and required disconnects means you have to know the specifics of the equipment you’ll be using as well as what the local juris- diction requires. Typically, the inverter needs to have disconnecting means (both AC and DC) within sight of the inverter.   The majority of the inverters on the market today have integrated disconnects, but they aren’t all considered AC and DC disconnects, which means you need to know for sure what type of product you’re using.

If the inverter doesn’t have integrated disconnects, make sure it has disconnects next to the inverter and in locations that satisfy the National Electrical Code (NEC). In addition, some utilities require visible, lockable disconnects at the utility’s meter location. If this is a requirement at your client’s site, become familiar with the utility requirements before conducting a site survey so you aren’t surprised later.

Ask the utility for its net metering or PV interconnection rules. If the utility does have a requirement, make sure you reserve the prop- er space for the required disconnect.    The electrical connections are a critical part of the whole installation.

Before you get too far into the system design, how-ever, you need to know what the licensing requirements are in the juris- diction in which you’re working. Some jurisdictions require that the people doing certain portions of the work hold specific licenses. (The most common example is the requirement that a licensed electrician make the final wire connections from the inverter to the utility.)

Consequently, you may need to hire certain tradespeople to do certain portions of the work.    To find out the requirements in the state where you’re working, visit the state’s construction contractors board or licensing department Web sites. These sites will list the requirements for working in the construction trades. 

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