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The Impact of Monday’s Great American Eclipse on Solar Energy

On Monday, August 21, 2017, millions of Americans will gather to watch the ‘Great American Eclipse.’ An event like this is rare because its path takes it across the entire United States, leaving most of the country in total or partial darkness. Companies that rely on solar energy to operate power plants and data centers are preparing in advance, as the solar eclipse will have a significant impact on solar energy production.

The U.S. Energy Information Administration (EIA) expects that 1,900 utility-scale solar photovoltaic (PV) power plants in all will be affected. California is estimated to lose 6,000 megawatts of solar product for up to 90 minutes, while North Carolina is expected to lose over 2,000 megawatts.

The sun will be totally eclipsed for a range of 70 miles wide running from Oregon to South Carolina. Even in places like New Jersey or Maryland, a partial solar eclipse can hinder solar production on a power grid.

Preparation and Preservation

U.S. Energy Information Administration and NASA Chart showing impact of eclipse on solar energy production

Solar facilities have been preparing for this eclipse for months. They have created plans to ramp up and ramp down other natural energies to fill the gap of solar production. Utility companies are planning to use other generation assets like natural gas, hydroelectricity, wind and thermal to support the power grid. 

Solid backup plans have caused the EIA to announce that little to no realizability issues are expected in the U.S.

However, public utility officials are asking businesses and residents around the country to reduce energy and save solar resources during the event, by doing the following:

  • Replace lightbulbs with LEDs
  • Turn off unnecessary overhead lighting in offices
  • Unplug appliances
  • Refrain from using unnecessary electronics
  • Turn off heating and cooling devices 

Financial Impact

GTM Research and SEIA map displays solar capacity state-by-state.

In most parts of the country, the eclipse will occur during 'on-peak' utility billing periods when demand charges are set.  Customer owned or leased systems can expect varying degrees of impact on their utility bills. The significance of the impact depends on how much energy is used between the time the sun is blocked and the eclipse is finished.

Demand charges are determined by the maximum energy consumption in 15 or 30-minute periods for an entire month. With the eclipse event lasting up to 90 minutes, monthly demand numbers could be impacted. For utilities that have ratchet clauses, the temporary loss of solar production has the potential for a year-long billing impact.  In addition customers will need to purchase kWh from utilities or third-party suppliers for the loss of their solar system output.

Next Steps

The last solar eclipse that passed over part of the United States was in 1979. As a country, we’ve made significant developments in solar and renewable energies since then. At the end of 2016, the U.S. had 40 gigawatts of installed photovoltaic capacity, more than double that of 2015.

This year’s eclipse will be a learning curve for the entire energy industry as it handles a drastic swing in solar energy production for the first time.

The next eclipse to move across part of the U.S. will be on April 8, 2024, stretching northeast from Texas to Maine. What we learn this year will help businesses and utility companies have more flexible backup energy sources in place for 2024.

About the author:

Tim Comerford is SVP of Biggins Lacy Shapiro’s energy services group and principal of Sugarloaf Associates. Tim is focused on assisting companies, developers, municipalities and real estate advisors with issues that pertain to energy procurement, renewable installation, infrastructure assessments utility relocation, with a special focus on mission critical facilities.


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