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Google Confirms PV Rooftop Solar Uneconomic

January 19, 2016

Google has recently unveiled a project to help homeowners determine whether they should invest in PV rooftop solar to save money. Inadvertently, Project Sunroof is demonstrating that PV rooftop solar is uneconomic.

Project Sunroof is being rolled out across the United States, but is currently only available in a few cities.

The Project Sunroof website uses a few specific examples to demonstrate the viability of PV rooftop solar at those locations.

The book Nothing to Fear provides similar information by state, using a program supplied by an installer. Google’s evaluation’s are probably more accurate because the satellite images of rooftops used by Google can discern shading by trees or other obstacles.

From Google Project Sunroof web site

From Google Project Sunroof web site

Using the data from the Project Sunroof web site, paybacks, without subsidies, are 13, 17, 12 and 27 years respectively, to recover the initial investment in Redwood CA, Somerville MA, San Jose CA, and Cary North Carolina.

The payback periods calculated by Project Sunroof are longer than those shown in Nothing to Fear.

The installer program used in Nothing to Fear estimates 8-year and 12-year paybacks for Los Angeles CA, and Massachusetts, and 16 year payback for North Carolina, but these estimates don’t include the cost of labor to install the PV rooftop system.

An acceptable financial payback is usually less than 3 years. Any investment that requires more than 3 years is probably not a good investment. Payback periods of 6 years or more are bad investments.

In all 50 states, only PV rooftop installations in Hawaii could be acceptable investments with payback periods of 3 years, as calculated using the installer’s program in Nothing to Fear.

Google’s Project Sunroof is now the third method for calculating payback periods to demonstrate that PV rooftop solar installations are uneconomic.

The first method uses 0.75 kWh per square yard of solar panel, as used by the University of California, San Diego, and as shown in Nothing to Fear: The second, an installer’s program, also shown in Nothing to Fear: And third, Google’s Project Sunroof.

PV rooftop solar is a bad investment, and a bad use of taxpayer money.

Google’s Project Sunroof is now helping to confirm this.

Money wasted on a bad investment isn’t available for a good investment.

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Nothing to Fear explains why CO2 isn’t to be feared, that politicians are harming Americans by pushing the CO2 agenda, that mankind has benefited from using fossil fuels and can continue to do so, perhaps for 1,000 years.

The appendix itemizes payback periods for PV rooftop solar by state.

Nothing to Fear is available from Amazon and some independent book sellers.

Link to Amazon:

Book Cover, Nothing to Fear

Book Cover, Nothing to Fear

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4 Comments leave one →
  1. Rob bradley permalink
    January 19, 2016 10:58 am

    This would be a great post with a bit more meat and some links (like to the Google program) if you are interested.


    – Rob

  2. Tom Stacy permalink
    January 19, 2016 6:56 pm

    Hi Donn. Thanks for the interesting post. A couple things: What assumptions are made about net metered percentages of generation and about net metering rebate rates? Because if the utility offers retail for PV solar returned to distribution, there is an implicit subsidy at work that could make a significant difference in break even years.

    Second, I am concerned that perhaps superimposing a general ROI period on PV investments is not appropriate. In regulated states where generators are guaranteed a net profit of a certain percentage of capital, the guarantee mitigates most of the risk of loss of capital, which would bring the appropriate ROI percentage way down into the mid single digits, extending the risk-adjusted acceptable break even period by several years and possibly up to double.

    Finally, I wonder if Google assimilates snow cover and cloud percentage in their estimates. I believe NREL’s PV Watts generation and ROI model dues both. See

    • January 20, 2016 9:09 am

      I don’t have access to Google’s algorithms or calculations so I don’t know whether they include net metering, snow cover etc. My use of an ROI metric is based on making good investments by people or businesses. PV rooftop investments by homeowners or businesses involves the use of investment capital with ordinary market risks. As you say, investments by utility’s, as virtual monopolies, involve far less risk which is why their returns are regulated. For this reason, it’s not possible to equate investments by people or businesses in PV rooftop solar with any similar investment by a utility.
      I agree that net metering is a subsidy, and if any income from net metering is included in Google’s algorithm their payback years are even worse.
      Thanks for good questions.


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