Thursday, May 15, 2014

Solar Panels: One Year Later

We get questions about our solar array fairly often.  So, I hope this blog post answers some of them.  Our 3.36 kW array has been converting sunlight to electricity for just over a year.  Puget Sound Energy (PSE) hooked it into the grid in late April 2013.

Our Barn/Garage with 14 south-facing solar panels.   April 2013  

These panels do not replace our need to purchase electricity from PSE; they only supplement our power needs.

At its most productive, during the summer's long hours of sunshine, the array earns up to $22 each day. However, it's much more informative to look at a year's worth of data to get a realistic view of the payoff.

One year of power generation, by month (May 2013 - April 2014)

In the past 12 months our array generated over 3650 kWh (per PSE).  It has earned about $2100 (5% from a reduction on our monthly bill, and 95% from Washington State's Renewable Energy Cost Recovery Program at $.54/kWh).    The chart below provides a monthly comparison between our electric bill as though we didn't have solar, and the amount we earned each month from the array.  (Note: Although the Renewable Energy Payment is received in a yearly check, I broke it down monthly for this chart.)

Month Bill if No Solar Solar $ Earned
May 13 $52 $224 
June 2013 $56 $271
July 2013 $71 $307
August 2013 $61 $224
September 2013 $63 $182
October 2013 $57 $121
November 2013 $68 $89
December 2013 $118 $55
January 2014 $73 $68
February 2014 $80 $106
March 2014 $47 $165
April 2014 $47 $223

As you can see, our earnings exceeded the cost of our usage for all but 2 months.

In addition, we received almost $5800 as a tax credit on our federal return.  And, we saved about $1650 in Washington State's sales tax waiver.

At this rate, we should break even after 7 years of power production.  We will earn the equivalent to a savings interest rate of 2.6% at 10 years; or 3.2% at 15 years; or 4.4% at 20 years. That's a decent long-term financial investment, but certainly not the best.  For me, however, our investment in sustainable clean power trumps the mediocre financial returns.

Here are some details about our 3.36 kW Photovoltaic Grid Interface System:
  • Spec'ed out and installed by Western Solar, 2 year installation warranty
  • 14 mono-crystalline solar modules from Itek Energy, 240W each, 10/25 year workmanship/power warranties
  • 7 Blue Frog Solar micro-inverters, YC-500 (1 micro-inverter per two panels), 25 year warranty
  • APS Energy Communication Unit (ECU), 3 year warranty
  • We do not have a bank of batteries, the power is fed directly into the grid
Other components include the junction box, combiner panel, breakers, meters, mounting hardware, etc.

The ECU is networked so that we can monitor the health and production of our array via the Internet.  The bar graph above is from our ECU.

I've made the information on our ECU public.  If you'd like to see both real-time and historic production data from our solar array, click on this link: Carlson Solar Energy Monitoring and Analysis or on the photo of our barn/garage in the right-hand column.