Renewable California

California is considered by many to be a world leader in the transition to renewable energy. But how much progress is it really making? This post looks into this question and finds that California has indeed significantly increased the percentage of renewable energy in its in-state generation mix – or at least would have done were it not for the impact of the recent drought on hydro output – but that it has made no progress towards increasing its zero-carbon generation, which because of the shutdown of the San Onofre nuclear plant remains lower than it was in 2002 even when the impact of the drought is factored out. This result underscores the importance of nuclear as a key ingredient in reducing CO2 emissions, a fact which seems to have escaped California’s attention.

California’s total generation

Figure 1 shows California’s generation mix since 2002, the first year for which complete data are available. (All the data presented in this post are from the California Energy Commission almanac unless otherwise specified):

Figure 1: California annual total generation 2002-2015 (2015 import data from Forbes)

Over the last 14 years California’s generation mix has consisted of roughly a third natural gas, a third imports and a third a mixed bag of nuclear, coal and renewable – mostly hydro – generation, although gas and imports have generally increased in importance in recent years. The 2015 generation mix is made up of 38.2% gas, 36.5% imports, 19.3% renewables and 6.0% nuclear. (Note that the flattening of total generation since 2008 is largely a result of the 2008 global recession. This pattern is repeated in just about all the developed countries.)


To segregate the entire generation mix by source, however, we need to know how California’s imports break down. Figure 2 shows the data on imported electricity that the almanac makes available in its annual Total System Power reports , which cover the period 2002-2014:

Figure 2: Available data on California’s annual electricity imports, 2002-2014

The data are incomplete except for 2007 and 2008, when coal generation made up about half of California’s net imports. What happened in later years, when approximately half of the imported power is still not categorized? A 2015 study from SNL noted that up to 50% of Southern California’s imports “still comes from coal-fired plants” and presented the plot of coal deliveries to out-of state plants owned by California utilities shown in Figure 3. The plot tends to confirm that imports of coal-fired power continued to provide a large fraction of California’s imported power through 2014. The 2015 data show deliveries through July and would probably be similar to the 2014 numbers when the data from August through December are added.

Figure 3: Coal deliveries to out-of-state coal plants serving California 2010-1025. Data from SNL.But

But not all of the electricity produced from this coal goes to California. In December 2014 New Mexico regulators mandated a reduction in output at the San Juan plant and earlier in the year Southern California Edison sold its interest in the Navajo plant to Arizona Public Service. These reductions will show as credits on California’s emissions and coal usage balance sheets, but the San Juan reductions had nothing to do with California and SCE’s sale of Navajo won’t even reduce emissions if APS keeps the plant running at the same level. Navajo is simply a book transfer of emissions from California to Arizona, or as the Los Angeles times less charitably puts it, a shell game.

So what to do about California’s energy imports? I ignored them. Out-of-state plants are not subject to California regulations (which is why California utilities went out-of state in the first place), they allow California to claim credit for non-existent emissions and coal usage reductions and the data are woefully incomplete anyway.

In-state generation and installed capacity

In-state generation also provides an incomplete picture, but anything that happens, or does not happen, in California can unquestionably be laid at the feet of California’s energy policies.

Figure 4 shows California’s in-state generation mix from 2002 through 2015. Generation has historically been dominated by natural gas and remains dominated by natural gas, which accounted for 60.0% of total generation in 2015. Other notable features are:

  • The abrupt decrease in nuclear generation between 2011 and 2012, which was caused by the shutdown of the San Onofre plant.
  • The decrease in hydro generation during the recent drought.
  • The increase in solar generation since 2012
  • The lack of growth in biomass and geothermal generation
  • The decrease in total generation since 2006, with the balance made up by imports, as shown in Figure 1.

Figure 4: California annual in-state generation 2002-2015

In-state installed capacity since 2002 is shown in Figure 5:

Figure 5: California annual in-state installed capacity, 2002-2015

Since 2002 California has added more natural gas capacity (15,060MW) than wind and solar combined (11,132MW). The shutdown of the San Onofre nuclear plant in 2013 removed 2,133MW. There have been no significant changes in other generation sources, including hydro, biomass and geothermal.

Renewables penetration

Figure 6 now shows the percentage of renewables in the in-state generation mix as California regulators see it. Renewables penetration has increased from 14% in 2007 to almost 25% in 2015. It seems that progress is being made:

Figure 6: Percentage of renewables in California in-state generation mix. Includes solar, wind, biomass, geothermal and “small hydro”

But there’s a problem with this plot. For reasons best known to themselves California regulators don’t consider “large hydro” (more than 30MW) to be renewable and don’t include it in their renewables totals. When large hydro generation is added we see no increase at all (which is maybe why it isn’t included):

Figure 7: Figure 6 data with “large hydro” included

The reason Figure 7 shows no increase, however, is that the recent drought reduced California’s hydro output to around half normal levels in 2014 and 2015, and since the state of California can’t be blamed for the drought Figure 7 also gives a false impression of California’s progress in developing renewables. What would the plot look like if there had been no drought? I simulated this scenario by assuming that California’s in-state hydro generation continued at the average 2002-2011 level from 2012 onwards. The result is shown in Figure 8:

Figure 8: Figure 7 data assuming no drought. Simulated by setting total hydro output to 34.8GWh – the 2002-2011 average – from 2012 onward.

Now the blue line shows an increase comparable to the red line, along with 13% higher renewables penetration. Unfortunately California can’t use it because it isn’t what the data show.

Zero-carbon electricity

However desirable it may be to replace fossil fuel generation with renewable energy, a key goal of any renewables program is to reduce emissions, and this goal can be achieved only by increasing the percentage of “zero-carbon” generation in the mix. How has California done in this respect? Figure 9 shows the percentage of zero-carbon electricity, which includes nuclear as well as large hydro, in California’s in-state generation mix. The trend line shows a decrease from 48% in 2002 to 39% in 2015.

Figure 9: Percentage of zero-carbon generation in California’s in-state generation mix. Includes large hydro and nuclear generation.

Figure 10 shows the data with the impact of the recent drought on hydro generation removed using the procedure described in Figure 8. The trend line still shows a slight decrease:

Figure 10: Figure 9 data with the impact of the recent drought removed.

These decreases are a result of the shutdown of the San Onofre nuclear plant, which has more than offset any gains from wind and solar. Figure 11 shows what Figure 10 would look like if San Onofre were still operating. Even though Figure 11 adds only 2.1MW of nuclear – less than 3% 0f California’s total in-state installed capacity – the change is striking. Expanding nuclear will clearly be a key ingredient if California is to reduce its electricity sector CO2 emissions:

Figure 11: Figure 10 data with San Onofre nuclear generation included

Yet California continues to move in the opposite direction. Pacific Gas and Electric, the owner of Diablo Canyon, the state’s sole remaining nuclear plant, has just announced its intention to shut the plant down by 2025 after consultation with Friends of the Earth and other environmental groups. Apparently the state hasn’t yet been officially approached. PG&E’s rationale is given by PG&E Chief Executive Tony Earley, who:

acknowledged the changing landscape in California, noting that energy efficiency, renewables and storage are “central to the state’s energy policy. As we make this transition, Diablo Canyon’s full output will no longer be required,” he said.

It’s hard to say whether Mr. Earley really believes that California’s future energy needs can be met with wind, solar and energy efficiency alone or whether he is just bowing to pressure from California’s powerful environmental lobby. But if he really does believe in an energy future based entirely on intermittent renewables it may be time for PG&E’s customers to think about heading for the hills.

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31 Responses to Renewable California

  1. Dave Rutledge says:

    Hi Roger,

    An excellent analysis. I like the focus on electricity produced in California, rather than the official emphasis on electricity consumed in California. This also has the advantage of makeing the state statistics consistent with the EIAs.


  2. Jose A. says:

    Wait, when you say Palo Verde (the arizona NPP) you mean San Onofre, right?

  3. Charles 16 says:

    The plot in figure 3, does that only account for coal deliveries from January to July 2015? The asterisk points to a note below the plot

    • You’re right. That’s what happens when you don’t read the fine print. But I don’t think it alters the basic conclusions in this case.

  4. singletonengineer says:

    You have created a good source document, Roger. I’m a pessimist when it comes to carbon emission reduction. Other pea and thimble games include exporting polluting industries to other countries (eg to China). I cannot see any transparency regarding international air travel and air and ocean freight, both industries which are substantial carbon emitters and both of which are opaque when it comes to accounting… or so it seems to me.

    • Leo Smith says:

      I’m a pessimist when it comes to carbon emission reduction./i>

      If by that you mean we won’t, true.

      However if by that you mean ‘and it will impact negatively on the world’ well then no!

      • singletonengineer says:

        I’m not demanding that others agree with me.

        My personal stance is that climate change is a huge problem and that, unless our energy systems are decarbonised pretty darned quickly, then we are in deep trouble. That explains my pessimism.

        Those who disagree need not fear – I try not to be rude to anybody on the basis of their opinions.

        In addition, I very much admire this blog for its frequent well-researched and presented discussions of matters related to energy. The engineer in me hates to see charlatans and scam artists who deal in half-truths or worse re energy issues. Examples: the hydro/solar scam on El Hierro Island and the excuses given to the population of Venezuela for the failure of their State-run electricity system.

  5. steve says:

    My Mrs wants a Tesla after going in one in Holland.It impressed her going down the motorway driverless. Does anyone know how the electricity mix in the UK and California affect actual carbon emissions in terms of g/km. Just read that one crashed killing the driver when it tried to go under a white truck, thinking it was the sky.Probably still safer than being driven by the wife though.

  6. Euan Mearns says:

    The land of make believe. Import coal and gas fired electricity and imagine its not you that made the CO2. UK will likely go same route.

    • oldfossil says:

      As a first step, the US reduced smog emissions in the cities by moving them out into the country. Then they reduced them further by moving them into another country, China. Ingenious.

    • cafuccio says:

      UK will rather import nuclear from France and maybe hydro from Norway, isn’t it?

  7. Todd D. says:

    Some claim that EIA data accounts for rooftop solar, whereas state of CA data may not, I can’t imagine the rooftop data would make much of a difference, overall point well made, thank you.

    • Thinkstoomuch says:

      I was rereading stuff and just noticed that Todd had compiled a spreadsheet with the CASIO data through March 9th 2016. I think.

      Good job,

      • Thanks T2M. That’s good data to have.

        • Thinkstoomuch says:

          You are welcome of course, Roger. But the thanks should go to Todd.

          Also I don’t know if you noticed but EIA recently made hourly load data for the entire US available. It can be broken out in regions. But it only goes back a year or so and is not broken out for sources.

          Might come in handy for making guesses about a smart/super grid that spans 3000 miles by 1500 miles with widely seperated population centers. Just one of my thoughts but pretty much beyond me.

          Or other uses smarter folk around here might think up.

          Have fun,

  8. robertok06 says:

    Dear Roger:

    great post, as usual… but I have a hard time reading and understanding correctly Fig.6… the label on the vertical axis is “GWh”… the caption reads “percentage”. Same for the following figures, 7 to 11.

  9. robertok06 says:

    @roger andrews

    “For reasons best known to themselves California regulators don’t consider “large hydro” (more than 30MW) to be renewable and don’t include it in their renewables totals. ”

    I think this is the correct thing to do, and BP and others do the same.
    Large-scale hydro, run-of-river and dam, is essentially a baseload generating technology, while wind and solar are not (let’s forget about the few cases when thermal/concentration solar has tried to accumulate heat in molten salts, a pityful result).
    In fact even geothermal should be put in a different column, as it is basically baseload too.

    • Thinkstoomuch says:


      You are in error. Not all large hydro is baseload. Many, if not most Western US dams are now peaking units.

      For example Shasta Dam:

      First sentence. Just about its whole watershed is contained in CA.


      PS Shasta has a special place for me. Dad helped build it. Wish politicians were forced to take the tour of it, Hoover and Grand Coulee to get a picture of the size of the power problems.

  10. Greg Kaan says:

    An interesting study showing that the “duck curve” issue is rapidly getting worse

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