Installing a photo-voltaic solar panel system is something I have wanted to do for a long time. While I do have a strong technical background, I don't work in the solar industry, which means I had a big learning curve to work through.

My goal is to design & build a system that reduces the amount of electricity used from my local utility. I don't plan to ever get all my power from solar.

Here are some bullet points that represent what I intend to accomplish in the long term:
  • Start small to learn from this experience with less risk
  • Record the electricity generated by the panels for at least two years
  • Compare the data with the calculations. How do they compare?
  • Make a decision to expand the system

Type of System

The system I am about to describe here is called a grid-tie system. There are no batteries. If the solar panels produce more power than what the home is using, power will back-feed into the utility's power grid. If you have a bidirectional meter (see NetMetering below) then your meter will literally run backwards when this occurs. From a logical standpoint, the grid now performs the same role a bank of batteries would perform. The grid stores unused energy by day and gives that energy back at night.

Also note that all grid-tie solar systems have a safety feature in them that disables power from the panels if power from the utility grid goes down. That's right. It means you cannot use your solar panels if the power from your utility company is out. This is a safety feature.  We don't want to back-feed power onto the grid when the grid is down.

Estimating Annual Cost Savings

I admit it. I didn't start with this step first. I simply knew I was going to install some kind of a solar electric system. In most cases, you probably should do this step first, if not for you, then for the wife.

I created a spreadsheet to perform the calculations described below.

  1. Obtain your home's past electric usage data from your utility. I was able to log into the Ameren Illinois website and download two years of history. You will need the dollar amount of your monthly bill and the amount of power consumed in kilowatt-hours (KWh). If your utility also provides your home with something other than electricity, natural gas for example, then make sure and exclude that from the dollar amount. Put the monthly dollar amount and electric usage into two columns in a spreadsheet.
  2. Go to the NREL PVWatts website, enter your zipcode, and record the number of average hours of sun per day for your location. In my case, that number was 4.82 hours.
  3. Now enter the following equation into a cell in your spreadsheet:

System Size (kW) x Average Hours of Sunlight Per Day x System Efficiency x 30 days = Avg. Generated Power (KWh) Per Month

And in my case:

1.04 x 4.82 x 0.8 x 30 = 120.3 KWh/Month

Note that System Efficiency is assumed to be 80%.
  1. Now we can estimate what our past monthly electric bill would have been had we already installed the solar system. To do that, add a new column to your spreadsheet. Each cell should have the following formula:

Electric Bill – ((Electric Bill / KWh Consumed) x Avg. Generated Power Per Month) = Electric Bill Adjusted for Solar

  1. Now sum up each month's actual electric bill and sum up each month's bill adjusted for solar. Subtract the two, and you now have the estimated annual amount of savings.

Calculating Return on Investment

Now that we know our annual savings, calculating our break-even point is just a matter of knowing the cost of the solar system. As it stands right now, my solar system budget is $3,500, and my annual savings is about $165 per year as determined from the previous exercise. Working the math, that means it will take me just over 21 years to break even. But wait! Once we take into account the 30% federal tax rebate, we now break even in just under 15 years.  See, who says the federal government doesn't give you anything?  You should also Google for additional incentives at the state and even the local level. The State of Illinois has additional incentives, but what I'm finding is that the state funds are quickly used up each tax year.

For some of you, a 15 year return on investment might be too high. Over the following topics, I will review the hardware I chose to use and point out areas of potential cost savings.  The potential cost savings is on the order of several hundred dollars, but I will also identify any potential downside by doing so.

System Components

I knew the system would be composed of solar panels and some kind of inverter to convert the direct current from the panels into alternating current, but I didn't know much more than that. I had to learn about all the other widgets that make up a solar electric system (Translation: I Googled a bunch).

Here are the major components of the system:
  • DC to AC Inverter(s)
  • Solar Panels
  • PV Racking system
  • AC Safety Disconnect Switch
  • 20 Amp Double Pole Circuit Breaker
  • Enphase Ethernet Gateway (Optional)
  • Miscellaneous cabling and conduits to connect the components together
Click here for a bill of materials.

DC to AC Inverter

My idea of a traditional solar electric system consisted of a single, large inverter that converts the power from all the solar panels into household AC current.  

As I read, I learned about a different way of doing things. Rather than have a single, large inverter, the idea is to use a small inverter, or micro-inverter, for each and every panel in the system. The advantages include the ability to monitor the power output from each panel, rather than just the whole system, and better power output during partial shading conditions.

From what I've read, the Enphase M215 micro-inverter seems to be the most popular micro-inverter available. Additionally, the manufacturer has excellent documentation, including a long list of approved third party hardware that has been tested with the Enphase product

Solar Panels

There are two types of solar panels: monocrystalline and polycrystalline. While moncrystalline is the more efficient of the two, this is typically not the deciding parameter. What you want to look for are the power rating, price, and physical size of panel that best fit your application. If choosing an Enphase M215 micro-inverter, then you should also verify the solar panel is on the list of approved panels.

I chose to purchase 270W Suniva Optimus Series solar panels. These panels were about $95 more expensive than the lowest cost 250W panel I could find.  When looking strictly at price versus rated wattage, on paper 250W panels seem to be in the sweet spot. A 20 watt difference doesn't sound like much, but this article presents a convincing argument to go with a higher rated panel. 

Will paying $95 extra per panel be worth it? I don't know for certain. That's why I'm starting out small. According to the previously mentioned article, a higher rated panel will have better performance under non-ideal lighting conditions, which is most of the time.

PV Racking System

Solar panels need a metal framework to mount to. For that, I found the Ironridge website to be very helpful. They have an online system builder, called the design assistant, that will create a list of all the parts you need for your specific application. The Ironridge racking system is certified compatible with the Enphase micro-inverter.

AC Safety Disconnect Switch

My local utility requires a disconnect switch mounted next to the electric meter. The requirements were rather specific. It could not be the circuit breaker type. Instead, it had to be a knife-blade type with a visibly open gap between the switch contacts. This type of disconnect was surprisingly difficult to find. My local hardware stores did not have this type of switch. After much searching, I chose the Seimens LNF222R 60A non-fused disconnect, and I bought it from Newegg, of all places.

If your utility provider is Ameren, you will also need to attach a sign to the disconnect switch, which meets some rather specific criteria. Refer to the Distributed Generator Checklist for those requirements. 

20 Amp Double Pole Circuit Breaker

Because the Enphase micro-inverter is installed directly under each solar panel, the cabling from the circuit breaker panel to the solar panels is no different than traditional home wiring. If you are comfortable wiring a 240VAC circuit in your home, then you can wire this solar system to your home. Keep in mind that all electrical work should be in compliance with local electrical codes.

Enphase Ethernet Gateway
The Enphase Envoy Communications Gateway is an optional device that records the power generated from each Enphase micro-inverter in real-time. Once connected to your local home network, it will upload that data to an Enphase webpage, customized to your specific application. This service is provided free for the lifetime of the product.

For a great example of what this webpage looks like, you can view the Enphase solar system installed at Busch Stadium in St. Louis, MO.

The device itself is simple to install. It does not require any additional wiring to the micro-inverters.  It communicates with the Enphase micro-inverters over your home's 120vac power lines.  Simply plug the device into a 120vac receptacle, and then plug the device into your home router with the included Ethernet cable.

As cool as this device is, it is not cheap. This module costs $500. I chose to purchase it because I want to log real data over time, confirm my calculations, and then ultimately decide whether or not I want to expand my system. On the other hand, by not purchasing this module, the time to break even financially is reduced by by several years.

Cabling and Conduits
You will need to make a trip to the hardware store and buy the necessary wire and conduits to tie your solar panel system to your circuit breaker panel. In my case, I chose to mount the solar panels to the roof of my shed, which already had a 100 Amp sub-panel in it. I attached the solar panels to the sub-panel via 10/3 with ground inside a length of seal-tight flex conduit. Your application will be different.

Fill out the Paperwork (NetMetering)

NetMetering is the term that describes the agreement your local utility makes with you to buy back the extra power you generate. To do that, they must replace your existing electric meter with a bi-directional meter. To make this happen you must apply for it. That means filling out a bunch of paperwork. Yea, Exciting. Tell me about it.

The following steps are specific to Ameren Illinois. You will need to do your own research to determine the requirements for your own utility.
  1. Read Ameren's NetMetering webpage
  2. Fill out the NetMetering Application
  3. Visit Ameren's Distributed Generator web page.
  4. Fill out the Distributed Generator Level 1 application and obtain all the requested documentation
  5. According to the Distributed Generator Checklist it is recommended you create and include a one-line diagram representing how you plan to wire your system. This is what my one-line diagram looks like.
  6. Mail all documentation to the address given on the Distributed Generator web page. You will be contacted by phone by an Ameren representative shortly.
  7. Contact your local authority and apply for an electrical permit.
  8. After the system has been installed and inspected, you will need to fill out Ameren's Certificate of Completion and include the inspection approval from your local authority.
Are all the forms making your head spin? It seems to me the government is trying to discourage us from installing a solar electric system by making the application process as confusing as possible.

Buy the Components

Finding a place to buy the components was more frustrating than anticipated. I had trouble finding a reputable vender that was willing to sell in relatively small quantities. I was also looking for a seller that was more than a virtual storefront. Did they have a warehouse, or were they just drop shipping everything direct from the manufacturer? Eventually I found ecoDirect. Their customer service was very helpful, and they were willing to sell direct to the homeowner in the exact quantities I needed.

Shipping Costs
Prepare to pay through the nose for shipping costs.  The solar panels and rails for the racking system are too large to be shipped UPS and must be shipped freight. I paid just under $450 in freight costs to ship the majority of the components to my home address.

Notice that sites like Amazon and even Home Depot appear to sell the largest components with "free" shipping (Home Depot ships to your local store). However, ecoDirect's pricing, adjusted for shipping costs, was still better than these sites.

Money Saver
In hindsight, I could have saved $90 if I shipped to a commercial address rather than my home. The church I attend is just a few miles down the street, and they even have a loading dock. I know where my delivery address will be for any future freight orders!

Assemble the System

Finally, we get to the fun part. Before we do, however, I feel obligated to tell you that all work should be in a manner compliant will local electrical and building codes. Consult your local authority (e.g. city hall) for this.

Part numbers for all the widgets mentioned in the following steps can be found in the bill of materials.

Step 1: Verify the Condition of Your Roof!
Don't do what I did and wait until the day before to closely inspect the condition of the roof. I had to delay the solar panel installation by a day to re-roof the shed. Fortunately, the shed roof required only 8 bundles of shingles, and I had a friend with a roofing nailer (Thanks, Eric!).

Step 2: Envoy Ethernet Gateway
If you purchased the Envoy Ethernet Gateway, now is the time to plug it in. Plug it into a receptacle near the breaker panel and attach it to your home network. Use the included powerline Ethernet adapters if a network drop is not nearby.

When powered up, the LCD should display its IP Address. Remember it. You will need it later. 

Step 3: Racking System
Following the steps in the Ironridge XRL Installation Manual, bolt the rack to the roof. Some installers use a piece of metal flashing between each L-Foot and the shingles, while some installers do not. Instead of using a piece of flashing, I applied a generous amount of Roofing Sealant under and around each L-Foot.

Each L-Foot must be screwed into an underlying roof truss with a 3" lag screw. Note that finding the locations of each roof truss can be the tricky part. I was fortunate that my shed has a ridge vent and the previous re-roofing step required that I temporarily remove it. While the vent was removed, I was able to see and then mark the location of each truss.

Step 4: Microinverters and Engage Cabling
Following the steps in the Enphase M215 Installation Manual, attach the Engage Cable to the rack. Use enough cable management clips to keep the cable from touching the roof. Now bolt each microinverter to the rack and then plug it into the Engage cable. Mount an outdoor rated junction box to the rack and route the Engage cable into it. Lastly, tie everything together with a #6 solid copper ground wire.

Lastly, write down the serial number of each micro-inverter and its physical location in the array. You will need this later. 

Step 5: AC Disconnect Switch
Mount the AC Disconnect Switch. In my case, Ameren had to pre-approve the location.  Barring any unusual circumstances the location is most likely going to be right next to your electric meter. Mount any required singnage at this time as well.

In my case, the disconnect switch will disconnect power to both the shed and the solar panels mounted on top of the shed.

I wired the disconnect switch during this step. However, you may have to wait until the next step to wire your own disconnect if your design differs from mine.

Step 6: AC Wiring
Install the circuit breaker in the panel and pull a heavy guage wire from the panel to the junction box previsouly mounted to the solar rack. I used 10/3 Romex with ground. You may need to pass this wire through the AC Disconnect if your design differs from mine.

Make sure your wiring follows NEC and local codes. Use watertight conduit if the cable passes to the exterior.

Now make your terminations inside the junction box. The wiring should be straightforward. Wire nut the ground wires together, then the white wires, then the red wires, and then the black wires.

Step 7: Mount the Solar Panels
At this point everything, except for the panels themselves, should be pre-wired and both the circuit breaker and AC disconnect should be in the OFF position.

You are going to need a helper in for this step. These panels a slippery little devils!

Lay the first solar panel on the rack. Vertically center the panel to the rack rails next to the junction box. As you lay the solar panel down, connect the wires from the panel to the micro-inverter. The plugs are keyed such that you cannot plug them in wrong.

Verify the panel is precisely parallel to the rack. It is important to get this right the first time. If the panels are not parallel by even a fraction of an inch, it will become highly noticeable by the time you mount the third or fourth panel. I had to learn this the hard way, and in hindsight I wonder if there isn't some method or tool that can help align these things more precisely.

Once the panel is aligned to the rack and wired to the micro-inverter, clamp it down using the Ironridge clamps.  Now repeat this process until all your panels are mounted.

Step 8: Verify it Works
Your system should now be fully assembled and ready to go.

Flip the circuit breaker and the AC Disconnect to the ON position.  Now go get your laptop, tablet, or other network device and point a web browser to the IP address of the Enovy.  Take a minute to become familiar with the interface and configure a non-default administrator password.

Once familiar, find the option to begin a scan for new inverters.  It is under the Administration menu. This process took about an hour to find just four. Speed is not a feature of these devices. Once the Envoy has found the devices, it should start recording power generated on the LCD screen of the Envoy. 

Now go to the Enphase Enlighten website, create a free account, and then build your virtual array.  You will need the micro-inverter serial numbers recorded earlier. You can view my solar array by clicking here.

Step 9: Final Paperwork
Schedule a final inspection by your local authority. Once it passes inspection, complete Ameren's Certificate of Completion and submit that along with your inspection documentation.

You should be contacted by Ameren to schedule an installation time for your bidirectional meter.


After reading this site, you should have a better understanding of where to begin and what the overall process is like from start to finish.

After identifying my project budget, I also identified areas for further costs savings. Those areas where:
  • Purchase cheaper solar panels - Less power output, but saves $95 per panel
  • Ship to a commercial address rather than your home  - Saves $90
  • Do not purchase the Ethernet Gateway - No real-time data, but saves $500
Taking into account all these savings, the project budget becomes $2,530. This reduces the time to break even to just over 11 years.

Finally, note that the calculations on this page assume the cost of electricity from the utility remains constant over time. However, we all know that the cost of energy tends to go up.  As prices go up, the time it takes to pay back your solar system gets shorter.


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