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Capitol Power Plant
Capitol Power Plant
Capitol Power Plant
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38°52′58.35″N 77°0′27.06″W / 38.8828750°N 77.0075167°W / 38.8828750; -77.0075167

Capitol Power Plant in 2023, viewed from Interstate 695

The Capitol Power Plant is a fossil-fuel burning power plant which provides steam and chilled water for the United States Capitol, the Supreme Court, the Library of Congress and 19 other buildings in the Capitol Complex. Located at 25 E St SE in southeast Washington, D.C., the CPP was the only coal-burning power plant in the District of Columbia, and it now mostly uses natural gas.[1][2] The plant has been serving the Capitol since 1910, and is under the administration of the Architect of the Capitol (see 2 U.S.C. § 2162).

According to the U.S. Department of Energy, the facility released 118,851 tons of carbon dioxide in 2007.[3] In 2009, it switched to using natural gas, unless coal was needed for backup capacity. Though it was originally built to supply the Capitol complex with electricity as well, the plant stopped generating electricity in 1951.[1] In 2013, it was announced that the Capitol Power Plant would add a cogeneration plant that will use natural gas in a combustion turbine to efficiently generate both electricity and heat for steam, thus further reducing emissions. A 7.5 megawatt cogeneration facility was completed at the CPP in 2018.[2] In 2021 it produced 32,000 tons of carbon dioxide.[4]

History

[edit]
The Capitol Power Plant at the turn of the 20th century

The power plant was constructed under the terms of an act of Congress passed on April 28, 1904, and authorized in order to support two new office buildings that were then being planned. Now known as the Cannon House Office Building and the Russell Senate Office Building, these new offices required a substantial increase in energy supplied to Capitol Hill. In addition, the U.S. Capitol and the Library of Congress would also receive power from the new plant, along with all future buildings to be constructed on the Capitol campus.[5]

Originally called the "Heating, Lighting, and Power Plant," the Capitol Power Plant was one of the earliest 25 Hz alternating current electric-generating facilities in the United States. The original steam boilers were replaced in 1923. In 1950 the steam boilers were modernized and replaced with coal-fired steam generators; at the same time, the plant's electricity generating capacity had reached its limit, and the decision was made to abandon electricity production in favor of the local electrical utility. The expansion of the plant to support additional new construction was authorized in 1958, 1970, and in the early 21st century to support the opening of the Capitol Visitor Center.[5]

Controversy

[edit]
A Capitol Power Plant employee inspecting the equipment, from the Architect of the Capitol

Senators from coal mining states blocked a proposal in 2000 to use cleaner fuel for the plant. Senators Mitch McConnell (Republican of Kentucky) and Robert Byrd (Democrat of West Virginia), both from coal mining states, used their influence as two of the Senate's most senior members to block this proposal. In May 2007, CNN reported that two companies, International Resources Inc. and the Kanawha Eagle mine, have a contract to supply a combined 40,000 tons of coal to the plant over the next two years. The companies gave a combined $26,300 to the McConnell and Byrd campaigns for the 2006 election.[6]

In June 2007, Speaker of the House Nancy Pelosi announced the "Greening the Capitol" initiative.[7] The initiative's goal is to make the Capitol carbon neutral, and the power plant is a major obstacle to achieving this objective.[6] In November 2007, Daniel Beard, the House's Chief Administrative Officer, announced that he would purchase $89,000 worth of carbon offsets for 30,000 tons of carbon emissions. Beard made the purchase from the Chicago Climate Exchange.[8] On February 28, 2009, Pelosi and Senate Majority Leader Harry Reid sent a letter to the Architect of the Capitol asking him to create a plan to switch the power plant entirely to natural gas by the end of 2009.[9] This letter came just three days before a March 2009 scheduled protest (which happened despite the change).[10]

In response to the letter from Pelosi and Reid, the Architect of the Capitol replied on May 1, 2009 that the plant had been transitioning to natural gas and was prepared to switch completely to that fuel, using coal only as a backup source. In 2008, the plant had operated on about 65% natural gas and 35% coal, compared to 58% coal in 2005.[11] By 2011, coal use at the CPP was down to 5%.

In 2013, the Architect of the Capitol announced that it had "identified the construction of a cogeneration plant as the most environmentally and economically beneficial way to meet its goal to use natural gas 100% of the time." The new cogeneration unit would use 100 percent natural gas to provide power for the 23 buildings of the Capitol complex, which includes the Capitol Building, the House and Senate office buildings, the Supreme Court, the U.S. Botanic Garden and the Library of Congress buildings, among others. Not only will it reduce the use of coal on-site for the chillers and boilers, but it would provide 93% of the facility's electricity. This would allow it to replace inefficient, 45% coal-generated electricity bought from the grid with more efficiently generated, on-site electricity that uses no coal.[12] They completed the permitting process for this facility in June 2013.

Emissions

[edit]

Table 1: Summary of Point Source Emissions: District of Columbia in 2002 (Tons)[13]

Facility PM2.5 NOx SO2 PM10
Capitol Power Plant 83 129 483 84
Pepco Benning Road Generating Station 15/16 15 253 1467 67
Pepco Buzzard Point Generating Station 5 340 390 5
GSA Central Heating Plant 12 66 8 12
10 Miscellaneous Sources 12 529 320 14
TOTAL 127 1,317 2,468 182
Share produced by Capitol Power Plant 65% 10% 20% 46%

Table 2: Summary of Pollution Reduction at the Capitol Power Plant Following Transition to Natural Gas (Tons)[12]

Pollutants 2007 2008 2009 2010 2011
SO2 460.95 240.73 175.33 36.98 48.04
NOx 189.02 128.79 121.20 105.15 90.36
PM 114.08 33.09 39.09 32.92 19.09
Hazardous Air Pollutants - 39.62 29.68 6.03 8.40
CO2e 118,851 - - 83,103 78,862

Particulates

[edit]
The plant and I-695 at dusk

For a plant its size (roughly 1/100 the size of the typical 500 MW power plant), the Capitol Power Plant used to produce a remarkably high quantity of the type of particulate matter (PM2.5) most closely associated with human health effects. As shown in Table 1, in 2002, the plant emitted a full 65 percent of the PM2.5 emitted in the District of Columbia by fixed sources (excluding automobiles, buses, trucks, trains and shipping). With the two other large power plants in the District of Columbia closed, and the CPP transition to cleaner energy, all of the emissions have been significantly reduced.

Particle pollution, also called particulate matter or PM, is one of six criteria pollutants (PM, lead, mercury, sulfur dioxide, nitrogen oxide, and ozone) regulated by the Environmental Protection Agency. PM is a complex mixture of extremely small particles and liquid droplets in the air. When inhaled, these particles can reach the deepest regions of the lungs. Exposure to particle pollution is linked to a variety of significant health problems, ranging from aggravated asthma to premature death in people with heart and lung disease. Particle pollution also is the main cause of visibility impairment in the nation's cities and national parks.[14] Fine particles (PM2.5) are 2.5 micrometers in diameter and smaller; and inhalable coarse particles (PM10) are smaller than 10 micrometers and larger than 2.5 micrometers.[14]

In 2006, EPA tightened the 24-hour fine particle standard from 65 micrograms per cubic meter to 35 micrograms per cubic meter, while leaving the annual fine particle unchanged. EPA retained the annual fine particle standard at 15 micrograms per cubic meter. EPA retained the pre-existing 24-hour PM10 standard of 150 micrograms per cubic meter. Due to a lack of evidence linking health problems to long-term exposure to coarse particle pollution, the agency revoked the annual PM10 standard.[14]

References

[edit]
[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Capitol Power Plant

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from Grokipedia
The Capitol Power Plant is a cogeneration utility facility in southeast Washington, D.C., operated by the Architect of the Capitol to supply steam for heating and hot water, chilled water for cooling, and backup electricity to the U.S. Capitol and approximately 20 other buildings in the Capitol Complex. Established in to meet the growing demands of the expanding federal campus, the plant originally generated 25 Hz alongside , but electrical production for the complex ended in as the city grid assumed that role, redirecting focus to thermal distribution via underground pipes spanning miles. Its current 7.5 megawatt combined heat and power system, featuring natural gas-fired combustion turbines with backup, supports reliable operations through that captures for production, with a major completed in 2018 replacing aging infrastructure to boost efficiency and reduce reliance on outdated boilers. The facility drew environmental scrutiny in the late for its use of in legacy boilers—the only such operation in —despite the plant's minimal scale relative to national emissions, leading to its phaseout in following protests that highlighted its symbolic prominence over substantive impact.

History

Establishment and Early Operations

The Capitol Power Plant was authorized by an on April 28, 1904, to provide centralized for heating and to the expanding U.S. Capitol complex, replacing inefficient individual power plants in buildings such as the Capitol itself and addressing growing demands from new facilities like the . The proposal originated from Elliot Woods, who emphasized efficiency and modern technology in siting the plant near railroad tracks for deliveries and the for water supply. Construction commenced in , with the —a reused from a statue—laid that year, and the facility began operations in December 1910 as a coal-fired plant equipped with steam boilers and generators. Initially, it supplied steam via underground pipes for heating the Capitol, , and adjacent office buildings, while also producing electricity as one of the earliest 25-cycle (AC) generating facilities in the region. The original boilers, which supported remote distribution to multiple structures, operated until their removal in 1923 amid routine upgrades. By the 1930s, the plant had expanded to meet evolving needs, including the of refrigeration capabilities; in 1935, appropriated funds for central equipment to circulate chilled water for across the complex, establishing it as the world's first large-scale plant of its kind. A one-story completed in 1938 housed six refrigeration machines, enhancing cooling distribution while the core steam and electrical functions continued under the Architect of the Capitol's oversight.

Mid-Century Transitions and Expansions

In 1950, the Capitol Power Plant underwent a significant upgrade when its original steam boilers were replaced with modern coal-fired steam generators to enhance efficiency and capacity amid growing demand from expanding federal facilities. Concurrently, the plant's original refrigeration equipment was replaced, effectively doubling its air-conditioning capacity to better serve the cooling needs of Capitol complex buildings. By the 1950s, the plant transitioned away from , which had been part of its operations since , as the District of Columbia's commercial grid assumed responsibility for electrical power distribution to the campus, allowing the facility to focus resources on and chilled production. This shift reflected broader infrastructural efficiencies and the maturation of regional utilities, reducing operational redundancies at the plant. A major expansion was authorized in 1958 through legislation that increased the refrigeration plant's capacity from 8,800 tons to approximately 14,000 tons, directly supporting anticipated growth including the construction of the and the Capitol's East Front extension. These enhancements addressed the heating, cooling, and utility demands of newly planned structures, marking a period of adaptive scaling to accommodate mid-century congressional expansions without compromising reliability.

Late 20th-Century Modernization

In the 1970s, the Capitol Power Plant underwent major upgrades to its equipment and infrastructure to support expanded operations for new facilities, including the Rayburn House Office Building, House and Senate subway systems, the U.S. Capitol's East Front extension, and the James Madison Memorial Building of the Library of Congress. Congress authorized plant expansion in 1970, followed by hearings in 1972 on H.R. 14475 to fund improvements to the facility and its distribution system, enabling service to additional structures like the Madison Building completed in 1976. These efforts included the addition of a West Refrigeration Plant and an administration building, with construction of the operations building and west refrigeration plant specifically commencing in 1978 to enhance chilled water production capacity. Further modernization in the late 1980s focused on fuel infrastructure and efficiency. In 1987, the Architect of the Capitol assumed control of the coal yard previously managed by the General Services Administration, streamlining fuel storage and handling. By 1989, Boiler 3 was converted from coal to gas and oil firing, reducing reliance on solid fuels amid shifting regulatory and operational priorities for cleaner combustion. These changes addressed capacity strains from post-World War II growth while preparing the plant for late-century demands, though electricity generation had ceased in 1952, shifting emphasis to steam and chilled water distribution.

Operations and Technical Details

Facility Infrastructure

The Capitol Power Plant occupies 4.7 acres on the U.S. Capitol campus in , adjacent to the Capitol building and connected via underground tunnels for utility distribution. The facility consists of multiple buildings and expansions, including the original structure dating to 1910 and a one-story addition constructed in 1938 to house refrigeration equipment, with further enlargements in 1958 and 1970 to accommodate increased demand from campus growth, such as the Capitol Visitor Center. Core infrastructure includes steam generation systems featuring multiple natural gas-fired , which replaced earlier coal-fired units installed in the 1950s and original steam removed in 1923. A key component is the system, implemented in 2018, comprising two natural gas-fired turbine units with a combined electrical output of 7.5 megawatts, integrated with a derived from a converted to simultaneously produce , , and for efficiency. Electricity generation via ceased reliance on external grid sales after 1951, shifting focus to on-site for campus needs. The refrigeration plant supports chilled water production with six initial machines added in , whose capacity was doubled in 1950 through additional units and pumps, enabling cooling for across facilities like the U.S. Capitol, , and . Modernization efforts, including replacements and efficiency upgrades, have addressed aging equipment prone to breakdowns, ensuring 24/7 operation via four rotating 12-hour shifts of operators managing boilers, turbines, and distribution controls. Underground piping networks deliver steam and chilled water through a utility distribution system spanning the , minimizing surface disruptions while supporting over 18 million square feet of facilities.

Capacity and Energy Production

The Capitol Power Plant primarily generates for heating and chilled for cooling, serving 17 million square feet of building space across 23 facilities in the U.S. Capitol Complex. production, which ceased in 1951 after reaching capacity limits and shifting loads to local utility service, resumed in via a natural gas-fired system. This facility has an installed electrical capacity of 7.5 MW, featuring a paired with a that captures exhaust heat to boost steam output and improve overall efficiency. The system operates mainly for backup power to ensure reliability during grid disruptions, rather than continuous baseload generation. Recent operational data indicate 12.7 GWh of produced from September to December 2024, reflecting intermittent use aligned with its reliability role. While precise annual volumes for and chilled water remain undisclosed in , the plant's infrastructure—including legacy units from the providing nearly half the capacity—handles peak loads for the campus.

Fuel Sources and Combustion Processes

The Capitol Power Plant primarily utilizes as its main fuel source for generating and , following a transition initiated in the mid-2000s to reduce reliance on . This shift began with increased usage starting in 2007, reaching over 90% of fuel input by the early , supplemented by low-sulfur distillate for backup and emergency operations. combustion was largely phased out by 2009, dropping from approximately 49% of fuel burned in 2007 to negligible levels thereafter, in response to environmental pressures and improvements. Distillate serves as a secondary fuel, limited to short-term peaking or reliability needs, with recent permits authorizing its use in dual-fuel systems alongside . Combustion processes at the facility center on boiler-fired steam production and via gas turbines. In the main boilers, undergoes controlled with air in fire-tube or water-tube configurations, heating to produce high-pressure (typically at 150-200 psi) for distribution to Capitol complex buildings for heating and absorption chilling. One boiler has been retrofitted as a (HRSG), capturing from exhaust gases rather than direct fuel , enhancing overall to around 80% in combined heat and power mode. The system, operational since the 2010s, employs a 7.5 MW where is ignited in a continuous-flow , expanding hot gases to drive the blades and an attached generator for on-site production. exhaust, at temperatures exceeding 500°C, is ducted through the HRSG to boil water and generate supplementary , minimizing waste compared to separate power and heat generation. Backup distillate oil can be injected into the or boilers during supply disruptions, with controls including low-NO_x burners to limit formation from high-temperature reactions between nitrogen and atmospheric oxygen. These processes prioritize reliability for the plant's service to 23 Capitol buildings, producing over 1.5 million pounds of per hour at .

Distribution and Service Area

The Capitol Power Plant operates as a district energy system, generating and distributing high-pressure for heating and domestic hot , as well as chilled for cooling, exclusively to facilities within the U.S. Capitol Complex on in This service supports approximately 23 buildings, including the U.S. Capitol, office buildings (Cannon, Longworth, and Rayburn), office buildings (Dirksen, Hart, and Russell), the U.S. Supreme Court, the , and ancillary structures such as parking garages and the former page dormitory. Distribution occurs via an of five walkable utility tunnels and direct-buried , spanning several miles to connect the plant—located at 25 E Street SE—to the served facilities. These tunnels house lines operating at up to 225 pounds per square inch and chilled water lines, enabling efficient delivery without reliance on external utilities for thermal energy needs. Electrical power generation ceased in 1951, with current units (7.5 megawatts total capacity, added in phases through 2018) primarily supporting on-site chillers and production rather than external distribution. The service area is geographically confined to the Capitol Complex boundaries, roughly encompassing the area bounded by Independence Avenue to the south, to the north, and extending eastward from the Capitol dome, covering about 270 acres of federal property managed by the . This centralized system enhances reliability for critical government operations but does not extend to broader District of Columbia or commercial districts.

Environmental Performance

The Capitol Power Plant (CPP) has been responsible for the majority of associated with the U.S. Capitol Complex facilities, comprising approximately 96 percent of the complex's total GHG output as reported in 2007. In 2006, the plant's consumption of 17,108 tons of generated roughly 60,000 tons of CO2, reflecting its heavy reliance on coal-fired boilers at the time. A shift toward natural gas as the primary fuel began in 2008 under the "Green the Capitol" initiative, displacing coal and fuel oil usage and thereby lowering emissions of sulfur dioxide (SO2), nitrogen oxides (NOx), and particulate matter due to natural gas's lower impurity content and more efficient combustion relative to coal. This transition aligned with broader regulatory pressures and efficiency goals, though coal remained available for backup. By 2015, natural gas dominated operations, contributing to sustained reductions in criteria pollutants. The commissioning of a 7.5-megawatt system enhanced overall efficiency by simultaneously producing , , and chilled water, reducing dependence on the regional grid (from 91,146 MWh to 5,989 MWh annually) and limiting combustion to emergencies or testing periods post-implementation. This resulted in marked declines in SO2 and hazardous air pollutants (HAPs), alongside modest reductions in and fine particulates (PM2.5). Concurrent plantwide applicability limits () imposed caps at 197 tons per year (tpy), down from a prior equivalent of 925 tpy; PM2.5 at 35 tpy (from 82 tpy); and HAPs at 25 tpy (from 257 tpy). As of a 2025 draft air quality permit renewal, actual emissions reflect these improvements, with at 59.2 tpy, SO2 at 4.2 tpy, and CO2 equivalents at 79,150.6 tpy, indicating ongoing low levels of criteria pollutants but persistent GHG output tied to combustion despite efficiency gains.

Regulatory Compliance and Mitigation Efforts

The Capitol Power Plant operates under federal and District of Columbia air quality permits issued by the U.S. Environmental Protection Agency (EPA) and the Department of Energy and Environment (DC DOEE), ensuring compliance with the Clean Air Act through site-wide emissions caps and continuous monitoring. In , the EPA issued a final Plantwide Applicability Limit (PAL) permit establishing caps for , fine particulate matter (PM2.5), and greenhouse gases, facilitating a transition from to while limiting overall emission increases. These permits mandate periodic stack testing and recordkeeping to verify adherence to limits, such as at 25 parts per million (ppm) for -fired units in recent DC DOEE drafts. A primary mitigation effort was the phase-out of combustion, announced in May 2009 following congressional directives to switch to for all but backup use, which dramatically reduced oxides () by over 95 percent, oxides, and particulate emissions compared to coal-fired operations. The completed this fuel conversion by installing -fired boilers and units, eliminating the need for auxiliary emission controls like previously required for coal. This shift aligned with Clean Air Act standards without triggering major new source review requirements, as confirmed by permit approvals. Further enhancements include the project, operational since around 2020, which produces steam and electricity simultaneously, yielding a 6.5 percent reduction in and lower hazardous air pollutant outputs through improved . The facility maintains compliance via operational limits, such as opacity restrictions under 20 percent for and (SO2) caps at 110 nanograms per joule of gross output in updated permits. As of 2025, DC DOEE permit renewals continue to enforce these measures, with no reported violations in recent , reflecting proactive adaptation to regulatory evolution.

Comparative Impact Assessment

The Capitol Power Plant's cogeneration system achieves total efficiencies of 60-80%, substantially higher than the 33% typical for separate electricity generation and on-site boiler heat production, thereby reducing emissions intensity per unit of combined thermal and electrical output. This aligns with broader combined heat and power (CHP) benchmarks of 65-80% efficiency, which capture waste heat that would otherwise be lost in conventional power-only plants operating at 30-50%. As a result, the plant's operational model yields lower greenhouse gas emissions compared to procuring equivalent services from the regional grid, where transmission losses and reliance on higher-emitting sources like coal-fired units in the PJM Interconnection elevate the carbon footprint. Relative to prior coal-dominant operations, the 2018 cogeneration upgrade—fueled primarily by natural gas—has decreased greenhouse gas emissions by 6.5% and hazardous air pollutants by 18%, while replacing outdated 1950s boilers prone to inefficiency and breakdowns. Recent permit data indicate potential annual CO2-equivalent emissions around 79,000 tons, with NOx at 59 tons and SO2 at 4 tons, reflecting the cleaner profile of gas combustion versus historical coal use that contributed disproportionately to local particulates (e.g., 65% of D.C.'s PM2.5 in 2002). In absolute terms, these figures are negligible nationally; the plant's 7.5 MW capacity represents about 1/100th of a standard 500 MW facility, and its CO2 output pales against top U.S. emitters like the J.M. Stuart plant's 23 million tons in 2021. Compared to district energy peers or utility-scale gas , the CPP's localized service to 23 federal facilities minimizes distribution losses, enhancing net over grid-dependent alternatives, though its urban proximity amplifies localized air quality scrutiny despite overall reductions post-fuel shift. dominance aligns its emissions profile with low-end U.S. fleet averages for gas-fired generation (approximately 0.4 tons CO2/MWh), outperforming baselines by factors of 2-3 but trailing renewables in lifecycle impact.

Controversies and Debates

Environmental Activism and Protests

In March 2009, environmental activists organized the Capitol Climate Action, a large-scale targeting the Capitol Power Plant's use of for heating and cooling federal buildings in Over 2,000 demonstrators, coordinated by groups including the Rainforest Action Network, Chesapeake Climate Action Network, and , marched to the facility and blockaded its five main gates, halting deliveries and operations for the day without arrests. The action highlighted the plant's role as the District of Columbia's only coal-fired power facility at the time, which activists described as contributing significantly to local and , including 65% of fine particulate matter (PM2.5) from point sources in the area as of 2002 data cited by organizers. Protesters demanded phase out coal combustion at the plant in favor of natural gas or renewable alternatives, framing it as a symbolic challenge to federal reliance on fossil fuels amid broader climate legislation debates. Participants, including students from institutions like the who formed one of the largest delegations, emphasized nonviolent tactics such as human chains and symbolic coal deliveries to underscore the urgency of reducing carbon emissions from the facility, which supplied and chilled water to the Capitol complex and nearby offices. The event built on prior advocacy, including calls from religious and youth groups for clean energy transitions, and was praised by organizers for its disciplined execution despite inclement weather. The 2009 blockade contributed to subsequent policy shifts, as Congress approved converting the plant's boilers from coal to natural gas by 2013, reducing sulfur dioxide emissions by over 90% and eliminating coal use entirely. Activist groups claimed the protest accelerated this timeline, though federal officials attributed the change to regulatory compliance with Clean Air Act standards rather than direct pressure. Post-conversion, activism has shifted toward broader sustainability critiques, with limited subsequent protests specifically at the plant, focusing instead on ongoing emissions from natural gas combustion and calls for further electrification or renewables. Sources from participating NGOs, such as the Center for Biological Diversity, often amplify the plant's pre-2009 environmental footprint, while government reports emphasize measurable post-conversion improvements in air quality metrics.

Policy Disputes Over Fuel Conversion

In May 2009, bipartisan congressional leadership, including House Speaker and Senate Majority Leader , announced that the Capitol Power Plant would cease primary use of for heating and cooling the U.S. Capitol complex, transitioning to as the main fuel to reduce emissions. The (AOC) requested $10 million to redesign and convert the remaining -fired to capability, building on prior modifications where one had already been adapted for heat recovery while retaining use. This shift addressed environmental concerns, as the plant had operated on approximately 65% and 35% in 2008, with no burned since March 2009 pending full implementation. Environmental advocacy groups, such as the Center for Biological Diversity, supported the conversion, arguing it would eliminate even in emergencies by adapting additional boilers, thereby achieving over 95% reductions in sulfur oxides and other pollutants. However, policy debates emerged over retaining as a backup fuel in two boilers for reliability during or gas supply disruptions, as permitted under AOC operations. Critics, including District of Columbia residents and congressional figures like Representative , contended that the plant's reengineering for rendered routine use unnecessary and inconsistent with emission reduction goals, especially amid plans to potentially increase capacity that could elevate pollutants. Protests in 2009 and 2013 highlighted these tensions, with activists decrying 's health impacts on nearby communities despite the plant's small-scale operations relative to larger facilities. A 2008 Government Accountability Office (GAO) assessment of fuel switching from noted economic and regulatory challenges, with stakeholders viewing conversions of existing as feasible but potentially less cost-effective than new builds, influencing congressional deliberations on funding and feasibility for the CPP. By 2015, a GAO report criticized AOC's long-term energy planning for lacking updates post-transition, questioning the sustainability of hybrid fuel capabilities amid evolving regulatory pressures and reliability needs. These disputes underscored broader tensions between environmental imperatives for full and operational priorities for uninterrupted service to federal buildings, with no complete elimination of backup enacted as of the mid-2010s.

Economic and Reliability Considerations

The Capitol Power Plant (CPP), operated by the (AOC), incurs substantial operating costs to maintain steam, chilled water, and limited electricity production for the U.S. Capitol complex, totaling approximately $63 million in fiscal year 2014, influenced by factors including fuel procurement, staffing, and maintenance requirements. These expenses have been mitigated through efficiency measures, such as staff reductions and shifts to lower-cost , which analyses projected could yield annual savings of $7 million by optimizing personnel and fuel use. Broader AOC efforts, including energy savings performance contracts (ESPCs), have generated over $200 million in utility cost reductions across the portfolio since the early , with reinvestments supporting infrastructure upgrades and indirectly benefiting CPP operations. The 2018 cogeneration project, involving two 3.75 MW -fired turbines under a utility services contract, addressed aging while enhancing economic viability, with projected implementation costs of around $85 million including financing over 27 years. This initiative replaced unreliable 1950s-era coal-fired boilers prone to tube leaks and corrosion, reducing consumption and enabling self-generation of two-thirds of the needed for the plant's chilled water system, thereby lowering reliance on purchased grid power and associated variable costs. Overall, AOC-wide has declined by 50.8% from the 2003 baseline through 2020, exceeding interim targets and contributing to sustained cost containment amid fluctuating fuel prices, such as at $8.36 per thousand cubic feet in 2014. Reliability remains paramount for CPP, as it delivers uninterrupted heating, cooling, and backup power to 23 facilities spanning over 18 million square feet, including the Capitol, and office buildings, and the , where disruptions could impair legislative and judicial functions. Prior to cogeneration upgrades, frequent mechanical failures in legacy boilers compromised steam production capacity, necessitating contingency operations and elevating maintenance demands estimated at $10 million per unit for renovations. The system, operational since 2018, bolsters by producing and recoverable simultaneously, ensuring 24/7 service during peak demands and grid outages, while modern chillers offer 50% greater efficiency than predecessors. No major systemic outages attributable to CPP have been documented in recent assessments, underscoring its role as a dedicated, resilient source insulated from broader grid vulnerabilities.

Recent Developments and Future Plans

Cogeneration Initiatives

The (AOC) identified , or combined heat and power (CHP), as the optimal strategy for enhancing energy efficiency at the Capitol Power Plant in its Long Term Strategic Energy Plan, prioritizing it over alternatives like full or biofuel conversion due to projected cost savings and reliability gains. In 2013, the AOC secured final air quality permits from the District of Columbia Department of Energy and Environment (DOEE) to install two natural gas-fired units, enabling the plant to generate while capturing for and chilled water production, thereby reducing fuel consumption by utilizing that would otherwise be lost. Construction proceeded through a utility energy services contract (UESC) with Washington Gas Light, a public-private that financed the 7.5 megawatt (MW) system without upfront federal capital expenditure, with repayment structured via cost savings over 21 years. The units, capable of dual-fuel operation with No. 2 as backup, became operational around 2018, serving the heating, cooling, and partial electrical needs of approximately 18 million square feet across 25 Capitol Complex buildings, including the U.S. Capitol and congressional office structures. Post-implementation data showed a significant decline in use intensity, surpassing AOC reduction targets and yielding net savings to offset the project's costs. The CHP system improved overall plant efficiency to above 70%—compared to under 40% for separate and thermal generation—while cutting reliance on grid power and enabling black-start capabilities for emergency resilience. In October 2025, DOEE issued a draft permit renewal (6663-R1) for the units, confirming compliance with updated reasonably available control technology (RACT) standards and affirming their role in maintaining low-emission operations amid ongoing regulatory scrutiny. No further expansion announcements have been made public as of late 2025, though the AOC continues to evaluate CHP performance within broader goals, including potential integration with renewable inputs.

Efficiency Upgrades and Sustainability Measures

The U.S. Capitol Power Plant underwent a major efficiency upgrade with the installation of a 7.5-megawatt facility completed in 2018, which employs a -fired to produce and concurrently, thereby capturing that would otherwise be lost and reducing overall fuel consumption by over 10 million cubic meters of annually. This combined heat and power (CHP) system aligns with the Architect of the Capitol's (AOC) 2009 long-term energy plan, which identified as essential for meeting rising demands while improving beyond that of separate heat and power generation. Additional enhancements include the Rehabilitation and Preservation/Rehabilitation (RPR) project, which introduced new chillers and free-cooling capabilities, yielding a 20 percent improvement in chilled-water production efficiency by optimizing cooling processes and minimizing energy losses in distribution. The AOC has also upgraded the plant's production and distribution infrastructure, such as repairing steam and chilled-water systems to curb in-plant losses and enhance operational reliability, contributing to broader goals that have enabled reinvestment of utility savings into maintenance. Sustainability measures emphasize operational optimizations over fuel switches, including the integration of energy-efficient equipment and strategies to lower intensity per unit of output, as evidenced by reduced use post-cogeneration without reliance on less efficient backup firing except in emergencies. These initiatives reflect pragmatic priorities—prioritizing verifiable efficiency gains from heat recovery and system repairs—rather than unsubstantiated claims of rapid decarbonization, with empirical tracking via AOC reports showing measurable reductions in across Capitol campus operations.

References

  1. https://www.aoc.gov/explore-capitol-campus/buildings-grounds/capitol-power-plant
  2. https://www.aoc.gov/about-us/organizational-structure/office-chief-operations/capitol-power-plant-jurisdiction
  3. https://www.aoc.gov/explore-capitol-campus/blog/capitol-power-plant-century-service
  4. https://www.gem.wiki/Capitol_Power_Plant
  5. https://chptap.ornl.gov/profile/30/CapitolPowerPlant-Project_Profile.pdf
  6. https://www.aoc.gov/what-we-do/projects/cogeneration-capitol-power-plant
  7. https://www.gridinfo.com/plant/aoc-capitol-power-plant/63347
  8. https://www.nbcnews.com/id/wbna30561554
  9. https://www.theguardian.com/environment/2009/feb/27/coal-environment
  10. https://www.everycrsreport.com/reports/R40433.html
  11. https://www.districtenergy-digital.org/districtenergy/spring_summer_2020/MobilePagedArticle.action?articleId=1577230
  12. https://www.congress.gov/85/statute/STATUTE-72/STATUTE-72-Pg1714.pdf
  13. https://www.govinfo.gov/content/pkg/CDIR-2020-07-22/pdf/CDIR-2020-07-22-CAPITOL.pdf
  14. https://books.google.com/books/about/Capital_Power_Plant_Improvements_Hearing.html?id=xJrKY7Ag_A0C
  15. https://www.eia.gov/state/analysis.php?sid=DC
  16. https://thehill.com/homenews/news/19465-capitol-power-plant-to-stop-use-of-coal/
  17. https://doee.dc.gov/release/notice-public-comment-period-draft-air-quality-permit-6663-r1-architect-capitol-us-capitol
  18. https://www.districtenergy-digital.org/districtenergy/2012Q1/MobilePagedArticle.action?articleId=1748454
  19. https://www.gao.gov/assets/gao-15-436.pdf
  20. https://www.gao.gov/products/gao-07-227r
  21. https://www.govinfo.gov/content/pkg/GAOREPORTS-GAO-08-917T/html/GAOREPORTS-GAO-08-917T.htm
  22. https://www.washingtonpost.com/archive/opinions/2007/04/28/the-capitol-power-plants-impact/ee595778-6b93-4ef5-a7d6-86e3ea944c2b/
  23. https://downloads.regulations.gov/EPA-R03-OAR-2014-0701-0040/attachment_1.pdf
  24. https://www.epa.gov/archive/epapages/newsroom_archive/newsreleases/9ec87459555c2d1e85257a6900548fde.html
  25. https://www.federalregister.gov/documents/2013/04/12/2013-08697/notice-of-issuance-of-final-air-permit-architect-of-the-capitol-capitol-power-plant
  26. https://www.biologicaldiversity.org/news/center/articles/2009/e-and-e-news-05-01-2009.html
  27. https://doee.dc.gov/sites/default/files/dc/sites/ddoe/page_content/attachments/Capitol%2520Power%2520Comment%2520Response%2520Document%2520Final%2520V.2.pdf
  28. https://archive.thinkprogress.org/capitol-power-plant-becoming-cogeneration-plant-quitting-coal-2b2a480308a7/
  29. https://www.epa.gov/chp/chp-benefits
  30. https://www.eenews.net/articles/the-top-10-emitting-power-plants-in-america/
  31. https://www.catf.us/resource/analysis-lifecycle-greenhouse-gas-emissions-natural-gas-coal/
  32. https://www.nbcnews.com/id/wbna29471584
  33. https://grist.org/article/a-capitol-offense/
  34. https://www.cnn.com/2009/POLITICS/03/02/global.warming.protest/
  35. https://grist.org/article/mean-old-and-dirty/
  36. https://www.democracynow.org/2009/3/2/capitol_climate_action_thousands_converging_on
  37. https://www.biologicaldiversity.org/news/press_releases/2009/climate-action-03-02-2009.html
  38. https://www.uvm.edu/uvmnews/news/uvm-students-send-nations-largest-delegation-washington-climate-rally
  39. https://www.facingsouth.org/2009/03/climate-protesters-surround-capitol-coal-plant.html
  40. https://www.loe.org/shows/segments.html?programID=13-P13-00005&segmentID=2
  41. https://e360.yale.edu/digest/more-than-2000-protesters-blockade-gates-at-us-capitol-power-plant
  42. https://www.biologicaldiversity.org/programs/climate_law_institute/350_or_bust/capitol_climate_action.html
  43. https://www.gao.gov/assets/680/672716.pdf
  44. http://norton.house.gov/media-center/press-releases/norton-wants-aoc-to-reconcile-inconsistencies-on-coal-burning-at-capitol
  45. https://www.gao.gov/pdf/product/new-items-d08601r
  46. https://rollcall.com/2015/09/04/gao-questions-capitol-power-plant-transition/
  47. https://thehill.com/homenews/news/10772-gao-supports-staff-cuts-at-capitol-power-plant/
  48. https://www.aoc.gov/sites/default/files/2021-07/OCE_Report%20on%20Energy%20and%20Conservation_2021_verified.pdf
  49. https://doee.dc.gov/page/notice-final-air-quality-permits-capitol-power-plant
  50. https://www.renewableenergyworld.com/energy-business/capitol-power-plant-gets-approval-to-start-cogeneration-project/
  51. https://www.youtube.com/watch?v=TErtlYTu9P8
  52. https://www.aoc.gov/what-we-do/projects
  53. https://www.gao.gov/products/gao-15-436
  54. https://www.aoc.gov/sites/default/files/2021-07/OCE_Report%2520on%2520Energy%2520and%2520Conservation_2021_verified.pdf
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