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Installing a microinverter based
solar electric power system in 2009

See more details on my blog
Overview System
Financing Panel
Hardware Grounding Rail
I should note at the start that I am a Do It Yourself guy and as-such I choose not to pay a local solar company to install my system.  By installing my system myself I saved up to $9000, however I have relied on the help, support and considerable experience of my friend Naoto Inoue (owner of
Solar Market,) to specify the system components.  Once I settled on the specific components, I went shopping on the web.  This process took me several weeks of research so that I could fully understand all the specifications and interactions between the choices.  Installing your own system is not for novices.  It does cut the local dealers out of the loop and compromises their business so I don't recommend this approach to the casual reader of this web page.  The big web dealers can operate on a very low margin and offer deep discounts on the hardware that local dealers cannot reasonably compete with.  Local dealer/installers rely on installations and a reasonable markup to make a profit since the margin on the hardware is not very high.

Having given my disclaimer, if you are committed to installing your own system, then you should also look at a very helpful web site called Build It Solar where you will find many examples of self installed systems (including mine!).  Gary Reysa who built the site also installed an Enphase inverter based system with ground mounted solar panels, his very detailed web pages are a great complement to mine.

I also made an effort to use exclusively products made or assembled un the United States.  This reduces the embodied energy in getting them delivered to me and supports US businesses.

Until 2009 the way that solar electric installations were designed was that the panels were wired in series (called strings) to produce from 150 to over 400 Volts DC, then these strings were combined and fed into a big central inverter box that is typically several cubic feet in size. 

Shown at left are 2 Sunny Boy inverters by SMA Solar Technologies.  These are the ones that I had originally considered using.  At right is a complete Outback power panel.
I decided to use the
Enphase micro inverters that were introduced in 2009 for several reasons.  They are more efficient than a regular inverter because the DC wire run to the inverter is as short as possible.  These micro inverters mount directly behind each solar panel and convert the solar DC directly to 240 Volts AC right there behind each panel.  One of the many advantages is that each panel can operate independently, this eliminates shading issues that can cause poor performance.  In traditional installations solar panels are wired in series and if one panel is partly or fully shaded the performance of the whole string of panels drops.  So instead of one big central inverter, I will be using 21 small ones.  More about micro inverters on Wikipedia.

September 2011 update.
Enphase have released a study showing that their microinverters out perform PVWatts calculations by up to 8%.  They looked at regular string inverters and found that they underperformed PVWatts numbers by up to 8%.  So this validates my decision to invest in Enphase inverters.

The AC wiring from each micro inverter connect in a parallel sequence of up to 15 units.  They literally plug into each other like extension cords.  These circuits are then combined and fed into a sub load panel and then to main load center of the building.  See the wiring diagram at left that is specific to the M190 model inverters, and click here to see my own system wiring diagram.  The only difference in my installation is that I used a sub-panel between the inverter junction boxes and the main breaker panel.  While my small rural town does not require an electrical permit or inspection, I will be hiring a
NABCEP certified electrician to review all of my wiring and the whole installation, this also makes my system eligible for federal and state incentives.
Envoy MCUEnvoy EMY v1.1
Each inverter reports its performance to an
Envoy EMU unit (left) that then sends data to a web site so that you can track performance on a panel by panel basis.  The new model is at right - they made it attractive so it can be located in the home rather then hidden in the utility room.

You can see my Real Time Statistics on this page of my site including a live web cam view of my array and monthly performance updates.
My stack of 21 SX3175NQ panelsFor several years I have been monitoring the price of solar panels and they have been dropping significantly since December 2009 so this was another reason that we decided to jump now rather than wait.  Here is a link to the price survey that I have used.  A year ago I was seeing prices in the $4.80/Watt range, now they are at $3.35/Watt (June 2009) for the panels I need - that's quite a savings on a 3675 Watt system! 
(in 2017 prices are down below $0.60/Watt making solar power a very attractive option as the cost will be at grid parity or better in most states)

I would have liked to use
Evergreen solar panels but they are not compatible with the Enphase inverters.  My preference is based on the minimum embodied energy of the delivered panels.  ( 3/20120 update: Evergreen panels used to be made in Massachusetts before cheap Chinese imported panels drove them out of business in 2010.)

The original Solarex (now BP) solar breeder plantMy second choice was
BP Solar because they are made in Frederick Maryland.   I actually called the plant and confirmed that my panel's serial numbers were produced in April of this year right there in the plant that was originally the first solar breeder plant.   When Solarex first built the plant in the 1970's (at left) they used solar power to manufacture the solar panels.  While that is no longer true - the huge solar array degraded and is now disconnected - at least they are made on the East Coast as opposed to Japan or China where the hidden embodied costs include all the fossil fuel needed to deliver them from the other side of the planet.  So I am voting with my dollars to support "locally" made solar panels.  I did end up driving 60 miles to Solar Market to pick up the panels (shown above left) in my Escape Hybrid, and it took 2 trips to get them all.  (3/2012 update: BP is getting out of the solar industry and will no longer be manufacturing panels).

The panels I selected are the BPSX175NQ model that are rated at 175Watts in full sun.  The "Q" designation means that these panels have cosmetic blemishes.  This means that a computer controlled camera in the factory found that some cells were not perfectly aligned or other minor cosmetic cell discoloration and the panels are sold at a discount despite the fact that they perform exactly as well as a regular panel.  You may find other manufacturers that sell "blemished" panels at a discount.
Iron Ridge mounting rack - end viewThere are a variety of ways to mount solar panels and the only type of racking system that I am familiar with is the IronRidge XR1000 system.  This is because I had helped to Naoto Inoue the owner of Solar Market install 3 panels on the Quaker Meeting House in Damariscotta, Maine, where I am a member.  This hardware looks very well engineered and easy to install.  It also appears to be a good price/performance system. 

There are a lot of details and small parts required and I paid particular attention to system grounding components.  Solar panels need to be securely grounded for electrical safety and to meet electrical codes to pass inspections.
WEEB-DMC grounding clip goes between panel and railI have been reading John Wiles column "Code Corner" in Home Power magazine for many years.  He discusses electrical code issues related to solar installations, and helps to draft and revise the National Electrical codes as they pertain to solar installations.  He has always emphasized safe grounding practices and I am particularly concerned that my panels are well and properly grounded to prevent problems due to lightning and or electrical failures. 

WEEB grounging lug for solar mounting railsWiley Electronics makes a line of specialty
grounding connectors and clips known as WEEBs (Washer Electrical Equipment Bond)   These components ensure good electrical connections between modules and their mounting rails, and between the rails themselves to provide a safe electrical path to ground. 
I went to a big box hardware store to get the electrical parts needed to connect the 2 inverter circuits on the roof to a load panel with 2 15 Amp 240 Volt breakers.  This load center then wires over to the main breaker panel with its own 30 Amp 240 Volt breaker.  I spent about $120 to purchase a load center box, 2 15 Amp circuit breakers, a 50 foot roll of 8-3 romex, a 25 foot roll of 12-3 romex, 2 exterior junction boxes and all the connectors.  As an experienced electrical engineer I have no problem wiring this stuff in myself, but most folks would be well advised to hire a licensed electrical contractor for the 240 Volt wiring side of a project like this.

In the process of researching the hardware, I found a number of web dealers that were helpful and had excellent discounts.  I found many of then from the EcoBusinessLinks Cheapest Solar Panels page.  I learned that most of them are small companies that are very friendly and personable to talk to on the phone.  Most are not just "click to buy" based businesses and they all encourage you to call and talk to their knowledgeable and helpful staff.  As a geek I had to let go of my reluctance to pick up the phone, these folks are really helpful!

Disclaimer continued
After I found the best possible prices, I went back to Naoto at Solar Market to ask him if he would be interested in competing with these prices.  I was pleasantly surprised when he agreed to match what I had found.  Naoto and I already have a friendly business relationship in place - I sell him the
solar differential temperature controllers that I manufacture, and perhaps this influenced his decision.  He has beta tested my controllers for me in the past and has offered very constructive feedback about them.

I suspect that he will make enough profit to be worth his while since his time investment is quite small.  I did offer to pay him a consulting fee if he felt that I was pestering him with too many questions and he agreed to consider some kind of barter in the future.  (I later sent him a new model controller for free for him to evaluate in his home installation). 

I do not want to suggest that everyone make a practice of this type of deal, because this could hurt the solar industry.  Solar professionals exist as value added service providers in a specialized industry and as such rely on a reasonable markup on sales of equipment. 
Solar Market is one of the oldest solar dealers in the country and certainly in the state of Maine and I hope they remain in business indefinitely. 

However by purchasing locally that I am supporting the local economy and my friend's business rather than web dealers out of state.  It also means that I will have to pay state tax on everything - that comes to over $800.  But once again I feel strongly that this is the morally correct way to do this and keep the money local.  I also saved on delivery charges by driving down to Solar Market (about 1.5 hour drive) to pick up the parts in my Ford Escape Hybrid, and saved several hundred dollars in truck freight charges. 
Picking up the panels etc.
June 18, 2009
My Ford Escape Hybrid with solar panels stacked inside
I drove 60 miles to
Solar Market down in Arundel this morning in my Ford Escape Hybrid.  I got 30.5 MPG on the way down, and 32.3 on the way back with a heavily loaded vehicle.  Must have been that tail wind!  The Escape can barely fit the solar panels which are over 62" long, and I had to scoot my seat forward.  We loaded up 11 of the 21 panels and then fork lifted a crate of 8 - 18-foot lengths of rack mount rails onto the roof rack and secured it carefully.
Handing over the deposit check to Naoto
I handed Naoto a deposit check for $10,000 - it's not often that one writes a check that size.  Naoto was kidding about winning the lottery.  I will come back 2 more times to get the remaining 10 panels, hardware and all the Enphase inverters when they come in.  (It's a lot cheaper than paying for truck freight!).  That will take several weeks because the new M190 model is in high demand.