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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
Workshop with solar panels
Image updated November 2021 after replacing collectors with 5 375W panels on right
Home Power issue 136 coverHome Power articl first page
I wrote an article for Home Power magazine
(issue 136, April/May 2010)
that summarizes the project, click here to get a copy.

I am committed to sustainable living.   I have a separate page devoted to all the efforts we are taking in that regard.  This section of my web site documents my experience while researching, designing and installing a grid intertied solar power system in the summer of 2009. 

An early decision was to use the new microinverter technology.
 Instead of the panels being wired together to create high voltage DC that is sent to a large single inverter that converts the DC to the AC we use in the home, each panel has a micro inverter mounted right behind it.  The power is converted to 240 Volts AC right there at the panel.  This makes the system more efficient and more flexible.  It eliminates the shading issues that can compromise the performance of DC systems where panels are wired in series - shading any one panel in the series will compromise the whole string.  Also one can mix and match panels of different capacity allowing one to grow a system with a blend of panels as you can afford them.  Overall this system has a slightly better cost/performance characteristic.  More about micro inverters on Wikipedia.

The only disadvantage of installing a grid-tied solar system like this is that there is no battery bank.  So when the utility power fails the inverters automatically shut down to protect the line workers.  So we will still need to rely on our Generac automatic propane backup generator (purchased from a local big box hardware store) during power outages.  In recent years we have lost power for an average of 5 days each year due to 2 heavy snow storms, Maine winters can be brutal.  This cost us several hundred dollars in propane, so the trade-off of a battery-less system can get expensive on occasion.   But in the long run it is less expensive than installing and maintaining a battery bank.

Several other factors influenced our decision to go solar now (2009), low mortgage rates, recent drop in the cost of solar panels, and the federal tax incentive that allows us to take 30% of the cost of the system off our federal taxes.  (We did not get the credit we expected in the first year because we are self-employed more on that here).  Note that prices of solar panels have plummeted since I did this installation!

Maine's electric supply has one of the highest renewable ratios in the country, in 2009 about 30% of the electricity delivered comes from renewable sources.  In 2020 it is more than double that - mostly sourced from Canadian hydro. Read more about other states renewable energy portfolio here.  Also, here's a site that lists comparative electric rates for US states.

So my next task was to figure out how many panels I would need, and where to put them all.  Go to the next page to see what I learned.  Also if you want to see a similarly detailed blog about a ground mounted solar power system that also uses Enphase inverters like mine - take a look at Gary Reysa's site: Build It Solar. 

Project timeline
DATE Progress
June 6, 2009 Signed loan for project financing (home mortgage re-financing)
June 18, 2009 Picked up 11 solar panels and the rack mount rails.
June 25, 2009 Re-roofing the building
June 26, 2009 Installed interior load panel for the 240 Volt power from the inverters
June 30, 2009 Picked up 10 more solar panels
July 26, 2009 Installed mounting rails for solar panels
August 1, 2009 Installed grounding wire for the rails, and roof junction boxes
August 14, 2009 Installed the first 12 (of 21) inverters
August 28, 2009 Installed the first 12 solar panels
September 3, 2009 Installed 9 more inverters
September 4, 2009 Installed the last 9 solar panels
September 16, 2009 More details and real time performance statistics
March 3, 2010 Article I wrote about the project published in Home Power Magazine
August 18, 2010 Installed 2 more 175 Watt panels (now have 23 panels installed)
June 29, 2011 Installed 2 more 175 Watt panels (now have 25 panels installed)
July 29, 2011 Installed 1 180 Watt panel (now have 26 panels installed)
June, 2012 Installed 3 230W panels (now have 29 panels all using M190 inverters for 5.2 kW total)
March, 2013 Installed 2 245W panels on south wall with Enphase M215 inverters (now at around 5.8kW total)
October 2016 Installed 1 245W panel on south wall of my house with Enphase M250 inverter.
ongoing As of 2021 I have replaced 11 of the 32 microinverters under warranty.
November 2021 Installed 5 375W panels on south facing shed (replacing solar heating collectors)