In extremely optimistic scenario for residential solar growth, output would still fall below 1% of 2020 electricity supply
Residential rooftop solar increased its output from 1.6 million megawatt-hours in the first four months of 2015 to 2.4 million megawatt-hours in the first four months of 2016. This according to the latest data of the Energy Department released Friday.
It's a large increase in percentage. Output from rooftops increased fifty percent.
At this high rate of increase, if it continued, January - April output would be 3.6 million in 2017, 5.4 million in 2018, 8.1 million in 2019, and 12.2 million in 2020.
Yet, utility-scale power sources produced 1,264.4 million megawatt-hours in the first four months of 2016. This amounts to 790 times the output of residential solar.
Suppose that residential solar output grows fifty percent per annum every year through 2020. And that the output of utility-scale power sources doesn't grow at all between now and 2020. Both assumptions are a stretch, but just suppose.
Then, during the first four months of 2020, utility-scale output would amount to 104 times the output of residential solar.
Let's express this conclusion in another way. Even in this extremely optimistic scenario for residential solar growth, its output would still fall below one percent of the nation's electricity supply.
Non-residential distributed solar produced 2.2 million megawatt-hours in the first four months of 2016, nearly as much as residential. If non-residential grows at a rate somewhat similar to that of residential, then this would further dilute the market share of residential in 2020, below the one percent level.
Indeed, utility-scale solar produced 9.7 million megawatt-hours in the first four months of 2016, six times as much as residential. In the highly-improbable scenario in which residential solar grows fifty percent per annum every year and utility-scale solar doesn't grow at all, then residential would finally pass utility-scale in 2020.
Data geeks, this is for you. The Energy Department now makes credible monthly estimates of residential solar output, including both the output that is used within the home and that sent to the utility grid, based on installed capacity.
Also, while the first four months of a year (January - April) are not when residential solar produces the most power, neither are the last four months (September - December). Statistical comparisons are valid as long as one uses comparable periods. The nation does need to produce power in the first and last four months of the year, if not from residential solar than from other sources.
Shining a light on past, present and future trends, Public Utilities Fortnightly.
Steve Mitnick, Editor-in-Chief, Public Utilities Fortnightly
E-mail me: mitnick@fortnightly.com
