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How Important is Baseload Generation Capacity to U.S. Power Grids' Reliability?

John Miller's picture
Owner-Consultant, Energy Consulting

During my Corporate career I provided manufacturing with power generation facilities’ technical-operations services and held different technical and administrative management positions.  In order...

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Recently a number of Politicians and Special Interests have advocated that the U.S. Power Sector’s ‘Baseload’ power generation capacity is outdated and rapidly becoming less important to maintaining Power Grids’ reliabilities and efficiencies.  This position appears to be based on a number of recent years’ power systems’ performance factors, including significant power generation-mix changes, technology developments, and continuously sustaining major U.S. Power Grids’ reliabilities.  Major power generation mix changes have included the recent large growth in Wind & Solar ‘Variable Renewable Power’ (VRP) generation, decline of Baseload Coal Power generation to a 34-year low, and very large increases of Natural Gas Power.  Yes, these factors are accurate, but how important has total Baseload Power net generation actually been in supporting past-current Power Grids’ reliabilities and sustaining future reliability?

Baseload Power Importance Political and Special Interests’ Views and Opinions – Power Grids are fairly complex and require many different technologies to reliably met electricity demands with adequate generation supplies.  The sources of power generation supplies have varied over the years and are very important to sustaining Power Grids’ reliable operations and managing costs.

The past Federal Energy Regulatory Commission (FERC) Chairman has reported “No new Nuclear or Coal plants may ever be needed in the U.S.” and that “baseload capacity is going to become an anachronism”.  These views or assumptions were made during the period when the Federal EPA was aggressively developing new Coal Plant emissions regulations, (reduced Hg, NOx, SOx, PM, etc.), and the Clean Power Plan (reduced CO2 emissions).  The combination of these and other Federal & State regulations (including the recent Paris Agreement) will significantly increase future Coal Power Plants’ costs, resulting in increasing-early retirements.

Special Interest groups, such as the America Wind Energy Association (AWEA), also advocate that “There Is No Inherent Need for ‘Baseload’ Power”.  This position is partially based on an Analysis Group study commissioned (paid for) by the Advanced Energy Economy Institute (AEE) and the AWEA.  A recent AEE/AWEA report states that there is: “No Evidence That Changing Power Mix Endangers Electric System Reliability”.  The Natural Resources Defense Council (NRDC) has also developed similar arguments that “Baseload” (is) an Outdated Term for Todays Changing Electricity Grids”.

Yes, even though Wind & Solar VRP have increased to historic highs in recent years and Baseload Coal Power has declined to a 34-year record low, the North America Electric Reliability Corporation (NERC, 2016 Long-Term Reliability Assessment) has determined that U.S. Power Grids have continued to meet needed power grid reliability levels.  The NERC generally agrees with some AEE/AWEA/NRDC views, such as the value of Power Generation ‘diversity’.  The NERC clearly identifies that ‘Single Fuel Dependency’ is a real risk-threat to Power Grid Reliability; i.e. the Power Energy mix is one of the important factors to sustaining U.S. Power Grids’ reliabilities in past and recent years.

The NERC, however, identifies other very important issues that the AWEA/AEE/NRDC reports generally overlook such as the importance of ‘Resource Adequacy’.  The NERC’s recent Reliability Assessment clearly identifies the major importance of adequate Reserve Margins  in enabling all Power Grids’ Operators to sustain required reliabilities.  Required ‘Reserve Power’ totally excludes Wind & Solar PV VRP, which cannot be ‘dispatched on-demand’ as required to properly manage-control short-term Power Grid demand changes.  In other words, Wind & Solar PV VRP are ‘non-dispatchable’ power sources and can actually increase the need for added Reserve Power, such as Natural Gas Power, in order to reliably maintain Power Grids supply-demand balances; depending on the time of day and year, and, weather conditions.

Other factors apparently overlooked by the AWEA/AEE/NRDC is that all Power Grid Owners-Operators are required to fully comply with existing FERC Electric Reliability’ standards-regulations.  These regulations include mandatory NERC standards, developed over many years to maintain and improve U.S. Power Grids’ reliabilities.  Also, somewhat overlooked by some Special Interests has been the past development of ‘Smart Grid’ technologies, which have contributed to significant Power Grids’ reliability improvements by Owner-Operators for decades.  Growing Wind & Solar VRP has also directionally increased the need for past and recent improvements in Smart Grid technologies; developed and installed by Power Grid Owner/Operators, and many Consumers ins some cases.

The AEE/AWEA/NRDC have routinely reported that sustained Power Grids’ reliability is due largely to “gas-fired resources and renewable capacity together providing both around-the-clock power and the flexibility to cycle and ramp as needed to meet and sustain bulk power system reliability objectives”.  Unfortunately, this view/assumption is not fully accurate since the only reliable-fully dispatchable ‘renewable capacity’ that can provide “around-the-clock power…as needed to meet and sustain bulk power system reliability” is Hydro, Geothermal, Biomass (wood + waste) and Solar Thermal power generation; not Intermittent Wind or Solar PV VRP.  These VRP sources absolutely require increased backup/reserve Natural Gas Power currently-continuously in order to reliably provide power to all affected Power Grids 24-7, year-round.

Most Important Operating Factors that have Impacted Baseload Coal Power Generation and Sustained Power Grids’ Reliability – The U.S. Power Sector’s major sources of (net) power generation have changed substantially over the decades as follows:

Data Source – EIA MER Table 7.2b.  Note: NG + Other = natural gas + other gases, and Bio + Geo = biomass (wood + waste) + geothermal.

U.S. Power Sector’s net generation sources have changed substantially over the decades due to a number of factors including evolving technologies (nuclear and renewables developments), regulations (renewables subsidies and mandates that constrain Fossil Fuels Power generation emissions) and market factors (lower cost natural gas and Wind/Solar PV construction costs most recently).  Between 1949-2007 Baseload Coal Power was the major source of total U.S. Power Sector’s net generation supplies; 52% on average.  Since 2007 the combination of lower cost natural gas fuels, increased Coal Power regulatory costs, and growing Wind & Solar VRP generation, led to historic increased Natural Gas Power net generation and major reductions in Baseload Coal Power.  During 2007-16, Coal Power net generation declined to 1982 net generation levels, and, Natural Gas and Wind + Solar Power increased to record highs.  Today, Coal, Natural Gas and Wind + Solar Power provide 31%, 33% and 7% (respectively) of total Power Sector’s net generation.  Nuclear Power continues to be the 3rd largest power source, at almost 22% of the total.

U.S. Power Sector net generation has been reliably supplied by a combination of fully  ‘dispatchable’ power sources, or more commonly called ‘Baseload’ Power, and, a combination of ‘Intermittent’ plus ‘Peaking’ Power generation.  Over the past decades the net generation levels and mix of these major power sources have changed overall as follows:

Data Source – EIA MER.  The Baseload includes all ‘fully’ dispatchable Coal, Nuclear, Natural Gas (from coal-to-NG fuels switching), Geothermal, most of Hydro and large percentages of Biomass and Petroleum.  The balance, or Peaking + Intermittent Power is based on the difference of Total Net Generation Power minus the sum of Baseload Power. 

EIA Power Sector data clearly shows that ‘Baseload Power’ is the major source of electricity that has supplied required Power Grids’ electricity demands, and supported required reliabilities and maximum efficiencies over most years.

Since 1949, the Baseload and Peaking + Intermittent power generation mixes have changed significantly.  For example, refer to the following Baseload Power (net) generation mix:

Data Source – EIA MER.  The above data include 100% net generation from total Coal, Nuclear, and Geothermal, 80% of total Hydro, 50% of total Bio(mass) and Petro(leum), and the balance of coal-to-Nat. Gas fuels switching for displaced Coal Power generation

Not clearly or more thoroughly covered in the most Special Interests’ recent articles is the fact that during 2007-16 ‘fueling switching’ from coal-to-natural gas (NG) power generation, was the primary action that enabled the Power Sector to substantially reduce Baseload Coal Power generation, without risking Power Grid’s reliabilities.  In other words, Baseload Coal was primarily displaced by newly scheduled-operated ‘Baseload’ Natural Gas Power.  The 2007-16 growth in Hydro and Geo+Bio Power was 8% and 24% respectively (each), also helped decrease the need for about 2% of total (2007) Baseload Coal Power net generation.  The above plot includes an average of 80% of Hydropower; primarily due to the fact that essentially all Hydropower is fully ‘dispatchable’ and an average of about 20% is normally used for Peaking Power; similar to the balance of Natural Gas Power generation.

Yes, Wind + Solar Power generation increased substantially since 2007, but these VRP, Intermittent and ‘non-dispatchable’ power generation sources have no or extremely limited capabilities to displace fully dispatchable Baseload Power generation sources.  In order to maintain Power Grid’s reliabilities,  power generation sources must be able to address: peak demand, variable demand & supplies (24/7), and maintain Power Grid’s frequencies and voltages.  Yes, the AWEA has referenced the development of advanced Wind turbine-generator technology, which enable new-future Wind Farms to help adjust power systems’ frequencies as needed to help maintain Grids’ reliabilities.  But, this new technology has fairly limited capability & capacity to adjust Power Grid’s AC power system’s frequencies and voltages/amperages.  To more effectively/significantly control power system’s frequencies & voltages, unfortunately requires reducing wind turbine-generators’ ‘capacity factors’ below maximums, in order to more significantly increase and/or reduce power output as required to help control AC systems frequency & voltage performance; as many Natural Gas, Hydropower and some Petroleum ‘Peaking’ Power Plants routinely are capable.

The balance of Peaking + Intermittent U.S. Power Sector net power generation sources 1949-2016 are as follows:

Data Sources – EIA MER.  Note: Natural Gas, Petroleum, Biomass and Hydropower Peaking/Intermittent Power is based on the balance of net generation not used for Baseload operation(s).  Intermediate Wind & Solar Power covers 100% of these VRP net generation sources.

Even with Natural Gas Power increasingly displacing Baseload Coal Power since 2007, fortunately there is more than sufficient total available Natural Gas Peaking and Reserve Power capacity available to continuously meet Power Grids’ Intermittent & Peaking’ demands; and the minimum required Reserve Power levels as mandated by the NERC standards.

Future of Baseload Power Generation – Even though some Special Interests continuously advocate that Baseload Power capacity is not as important as (Intermittent) Wind & Solar VRP, they appear to imply that variable power sources can directly displace Baseload Power such as Coal.  This assumption is not significantly accurate.  First, fully dispatchable Baseload Coal Power can be and is normally operated continuously at fairly large-constant generation rates for extended periods of time; weeks, up to months.  Wind & Solar VRP is, however, non-dispatchable or reliably schedulable, and this power generation is a function of uncontrollable variables; time-of-day and weather conditions (wind speeds & cloud formations) for most any given day.  Only Peaking Power/Reserve sources, primarily Natural Gas and some Hydropower, can normally be displaced by Intermittent Wind & Solar VRP generation, or provide increase power generation as required when the wind slows or stops, clouds buildup and/or the sun sets.  The above plot/data clearly shows that prior to about 2006 Natural Gas Power generation was the major source of required Peaking and Intermittent power as needed to balance Power Grids’ supply with demand.  Beginning in about 2007 as new Wind Power was built/put in-service.  This Wind VRP generation source generally displaced only and increasing amounts of Peaking/Reserve Natural Gas Power, and possibly some small amount of Hydropower.  Since about 2012, Solar Power began to have significant impact on also reducing the need to Natural Gas/Hydro Peaking Power generation during the sunny part of the days.

The good news in recent years is that Natural Gas Power capacity was high enough to displace all Baseload Coal Power decreases since 2006 (fuels switching), and, enable the growth of Wind & Solar VRP up to almost 7% of total net power generation today.  Based on existing and planned changes-growth to Natural Gas Power generation in the future, there appears to be sufficient Natural Gas Power generation capacity available (per the EIA AEO 2017 ) to enable future expanding total Renewable Power (including Hydro) up to almost 30% total supply in 2050; without compromising U.S. Power Grids’ reliabilities.

In Conclusion – Baseload, fully dispatchable power generation has been the major contributing factor to the Power Sector and associated Power Grids reliabilities, and, keeping costs under reasonable control.  Baseload Power has provided the vast majority of Power Grids’ supplies since 1949, refer to the following data plot:

Data Source – EIA data.  Note: the Baseload percentage is based on the sum total of Coal, (fuels switching to) Natural Gas, Nuclear, Geothermal, 80% of Hydro and 50% of Petro+Biomass divided by total Power Sector net generation.

EIA data clearly shows that the majority of Power Sector electricity supply comes from (fully-dispatchable) Baseload Power historically and today.  Yes, technology and infrastructure improvements have reduced the level of Baseload Power required to reliably meet Consumers’ demand since the late 1980’s by about 10%.  This current level of Baseload Power can and will likely be further reduced in the future (without risking Power Grids’ reliabilities and substantially increased Consumer costs) as further Smart Grids and other technology developments evolve.  These overall technology improvements-upgrades will include increased ‘demand response’ and ‘power storage’, and further upgrading/optimizing ‘T&D lines’ systems and operations controls.  Since these and other Power Systems’ upgrades are costly and will likely take multiple decades to develop and install, Power Grids’ electricity supplies and required systems’ reliabilities will most likely continue to require large levels of Baseload Power generation, well into the second half of this Century.

Yes, Baseload Coal Power will possibly continue to decline, but at a rate and to levels highly dependent on the continued availability of Natural Gas Power, and its current low market prices.  The future of Nuclear Power development and retirements can also impact Natural Gas Power utilization and available-required Reserve Power.  Also, as Wind & Solar VRP continue to expand in the future, at some point possible limited availability of Natural Gas Power generation capacities and/or fuel supplies/increased costs could become a growing problem-limitation to the Power Sector’s reliability and generation costs.  Further developments in fully-dispatchable, Hydro, Geothermal and Biomass Power generation will definitely help, but the future of these technologies is significantly uncertain due to numerous economic, and in some cases, environmental constraints.

Your thoughts?

John Miller's picture
John Miller on Mar 18, 2019

Charles, agreed, growth in variable (unpredictable) renewable power generation could become very challenging to maintaining the future integrity (supply-demand balances and associated required systems’ stabilities & reliabilities) of possibly all centralized Power Sector Grid systems.  Fortunately, Natural Gas Power (variable and peaking) generation has increased significantly in recent years ( ), and has fully enabled controlled/reliable/cost effective replacement of Coal Power.  In addition, expanding Natural Gas Power generation has enabled large increases of variable/unpredictable Wind + Solar PV Power generation in recent years.  If Natural Gas Power generation were to be substantially-uncontrollably restrained/shutdown in the near future, possibly per the Green New Deal 100% renewable generation policy target, and, Industrial scale power storage (batteries) fails to become a reasonable technology-capacity factor reality very soon, yes, most Power Grids’ integrity’s, capacities (24/7) and overall reliabilities (chronic brown-and black-outs) will then very likely become a growing disaster for the U.S. Populous and Economy.

Joe Deely's picture
Joe Deely on Mar 19, 2019

John Miller's picture
John Miller on Apr 1, 2019

Joe, “instantaneous maximum demand’ refers to a very short period of time, not multiple hours and definitely not up to a third of a given day; or multiple-continuous hours of operation.  Also, when uncontrolled power generation, solar in this case, overloads given power grids, peaking power generation (natural gas) must be rapidly cut back; proportionally to increased/increasing solar.  In addition, the impacted power grid(s) will also export power (in some cases) to adjacent states as feasible, and/or eventually constrain solar PV generation as required.

Yes, as solar PV continues to increase there will be small increases in brief/instantaneous power generation records; within the power grids demand at that given-short moment and ability to reduce other generation (peaking sources) as required to balance power grid’s supply-demand; as required to properly operate-manage impacted power grids stabilities & reliabilities.  The problem statement or actual factual impacts with this data is that ‘baseload’ nuclear, coal, etc. cannot (in the vast majority of cases) be cut ‘instantaneously’ as required to off set this short time-period of increased solar power generation.

Joe Deely's picture
Joe Deely on Apr 2, 2019

Joe, “instantaneous maximum demand’ refers to a very short period of time, not multiple hours and definitely not up to a third of a given day; or multiple-continuous hours of operation. 

Actually John, solar was at or above 50% of demand for about 7 hours (10am-5pm).  Plus of course this does not include rooftop solar which would have reduced grid demand substantially during this same time period. Including rooftop would mean that solar provided about 65-70% of demand for this time period.

Below is the chart for that day as well as the hourly breakdown - in case you want to calculate the generation share for the day we are discussing.

In looking at the chart  and that hourly breakdown - would you say that nuclear is the "baseload" for CAISO? 

In past years, I might have said that imports were the "baseload" for CAISO, but as you can see imports actually went negative for several hours. Can "baseload" go negative?

John Miller's picture
John Miller on Apr 9, 2019

Joe, suggest you better check all relevant facts to your CAISO reference. The 50%+ of solar power generation on Mar. 17, 2019 is based on ‘low/zero carbon generation’ including Nuclear.  Yes, the 10K MW’s of solar generation (including imports) represented (10K/25.7K(demand)=) 39% of total demand for almost 7 hours, definitely set an amazing non-fossil fuel power generation record.  However, on an average-annual basis, CA solar power only provides a little over 10% of demand.

As far as how did CA Power Utility Companies manage their Power Grids supply-demands and systems stabilities during this record setting event, I suggest you do some further research, since it’s very likely power imports (annual average of about 30% of total CA supplies-consumption), very likely went ‘negative’.  How many CA baseload plants were cut back to minimum rates or shutdown (zero generation), depends on how the power grids were operated/managed during this 7-hour period of excess power generation from solar.

Joe Deely's picture
Joe Deely on Apr 11, 2019

The 50%+ of solar power generation on Mar. 17, 2019 is based on ‘low/zero carbon generation’ including Nuclear.

What does this mean?? The 50% number is only for solar.

If other low/zero carbon sources were included the number would be way higher. For example, yesterday morning the low/zero carbon share on CAISO grid was at 93%.

Yes, the 10K MW’s of solar generation (including imports) represented (10K/25.7K(demand)=) 39% of total demand for almost 7 hours

No John.. problem with your data there. I included the atual numbers above - why not use them? Here is the data betwen 10am and 6pm. Solar provided 54% of the total demand.

Your comment on "record setting event" implies that you think this  is not a regular occurence. With the growth in solar over the last few years this now happens most days during spring - especially on lower demand weekends.  Look at yesterdays data - Solar was again near 50% for daytime hours.

More importantly, for the full day renewables were at 42%. Natural gas was only 13% for full day.

April 10th,2019

In regards to your annual solar number for California - a couple of items, That data is for 2017 - totals will be higher for 2018. Those numbers do not include rooftop generation which would add another 3-4% to solar share. 

Rick Engebretson's picture
Rick Engebretson on Mar 20, 2019

I think the status quo energy options are about to look very foolish. "The Green New Deal" (TGND) is not a stupid goal as the fossil industry declares. But the windmill solar panel industry certainly helps make the TGND look stupid.

As measured by NASA, the earth is responding predictably to new CO2 and new agriculture needs by getting greener. Solar biofuels and fiber-glass roofing innovation are more than a little obvious energy opportunities the new technology economic super-powers are aware of.

Go ahead and battle it out over nothing. But don't ask me to jump into your trench.

Joe Deely's picture
Joe Deely on Mar 23, 2019

"Baseload" goes negative on CAISO.  Renewables at 67% of total generation. Zero carbon at 90%+.

Bob Meinetz's picture
Bob Meinetz on Mar 24, 2019

Joe, "baseload goes negative" - that's funny. Trying to pawn the problem of non-dispatchable, problematic solar generation off on baseload, eh?

Kinda like when a builder is cited for building a house too high for local codes, and tells the inspector, "It's not that the house is too high, the foundation isn't low enough!"

To avoid taking the blame for costing California ratepayers $1 billion/year in negative pricing, renewables advocacy will stop at nothing.

Joe Deely's picture
Joe Deely on Mar 24, 2019

Numbers on CAISO for Mar 23 (MWh)

  • Renewables: 182,344 
  • Imports: 106,244
  • Hydro, 79,715
  • NG: 76,680
  • Nuclear: 53,973

1) Renewables > Imports + NG

2) Total demand < 500 GWh due to rooftop solar

3) Rained across large chunks of the state morning/midday. Hence later solar peak.

4) compare to same Sunday 6 years ago. What will this chart look like 6 years from now?

Bob Meinetz's picture
Bob Meinetz on Mar 24, 2019

Joe, peak demand yesterday was at 8:30 PM when solar was generating something between 138 MW and...nothing. Let's assume 69 MW - that means solar was providing one-third of one percent of California electricity, when ratepayers need it most??
Here's an idea: what if CAISO demanded everyone stop using electricity when it rains across large chunks of the state, or after the sun goes down - wouldn't that be easier (and cheaper) than spending hundreds of $billions on batteries, then hoping it won't be raining when we need to charge them?

Joe Deely's picture
Joe Deely on Mar 25, 2019

Actually Bob as the chart states explicitly peak demand was at 19:53. 

NG at that point was almost at 3,900MW while renewables were about 6,000MW. Like you said Solar was near zero.

In a few years - 2022/2023 - as the first GWs of storage get added to CAISO grid - that NG number will be down around 2,000 MW and daily totals for renewables in Spring will consistently be above 250,000 MWh while daily totals for NG will consistently be below 50,000 MWh.

A few years after that - early evening NG on CAISO in March/April will be near zero.

We are just getting started on the battery learning curve.

In December 2018, BloombergNEF published the results of its ninth Battery Price Survey, a series that begin in 2012 looking back at data from as early as 2010. The annual price survey has become an important benchmark in the industry and the fall in prices has been nothing short of remarkable: the volume weighted average battery pack fell 85% from 2010-18, reaching an average of $176/kWh.

So we have solar getting cheaper every year and GWs of solar being added to CAISO every year. 

We also have batteries gettng cheaper every year. Initially these will 4 hour durations but development is already under way on longer term (16-18 hour) batteries.

Every year as more solar and storage is added NG generation will continue to get "eaten away".

One last thing - yesterday was the first Saturday since CAISO started publishing charts in 2010 where total generation was below 500,000 MWh.

Why? Rooftop solar is eating into grid demand.  About 1GW of rooftop is being added every year.  I wonder if a bunch of those Tesla car owners will add storage to their solar.


John Miller's picture
Thank John for the Post!
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