GreenTown Los Altos

Los Altos resident shares solar story


Feb 2012


By John Bigler, Los Altos resident

In April 2006, we decided we were ready to “Go Solar” at our 2900 square foot Los Altos home.  Our goal was to reduce our eco-footprint by generating our own electricity.  After requesting bids from three different solar companies, we selected Mountain View based Cobalt Power Systems to design and build our rooftop Photovoltaic (PV) system.  Out of our 3 bids, Cobalt’s analysis and proposal was the most complete and personalized to our needs.  Upon reviewing our options, we chose a grid-tied PV system, where we generate and use our own solar power during the day, and use the PG&E power grid for our overnight electrical needs.  Given the high reliability of the power grid in the Bay Area, we could not personally justify the option of installing a battery backup system for overnight power or to cover our power needs during PG&E power outages.  During the day, when we generate more power than we use, the extra power feeds directly into the PG&E grid – and PG&E credits us for that over-generation.  After the sun goes down, we draw electricity from the PG&E grid and pay for it using our daytime credits.  To enable this daytime/nighttime tracking, we converted to PG&E’s Time-Of-Use (TOU) electric meter for our PV system.  Since installation, our electric bill runs about $6/month, simply for rental of this TOU meter.

We chose to size our new PV system at 5.88 kW to fully cover our monthly electric costs.  This is not to say that we generate more kilowatts than we use, but rather, that we earn more kilowatt credits than we spend.  The secret that makes this work is during the May-October (summer) timeframe, PG&E credits us at triple rates during the daytime hours when we are producing excess electricity since this is their peak demand period and they appreciate our extra power generation during that time.  To allow me to monitor our power generation, I also asked Cobalt to install a data link from our PV system to my computer so I could retrieve live and historical power generation data at my desktop.

As an early adopter of PV technology, the net cost of our system after rebates was relatively high.  At our current rate of savings, we are expecting our Return-on-Investment (ROI) on our 25-year system to occur somewhere around 16 years (10 years from now).  For homeowners installing in 2012, the recent leaps in design and efficiency should now produce a much faster 15% to 30% ROI per year (per Cobalt’s website).  Your PV bids should show you your expected ROI timeframe based on your specific system size and electric history.

Today, our PV system has been running for almost 6 years with zero PV downtime and zero required maintenance.  All I have to do is rinse our rooftop panels about twice a year.  We are very happy we made the leap to Solar.

For more information on solar, and GreenTown’s upcoming solar group purchase program, email

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