Company lists · Data refreshed August 2026

Top 25 Clean energy consultancy companies based in the United States

Name: Clean energy consultancy companies based in the United States
Creator: RevenueBase
License: https://creativecommons.org/licenses/by/4.0/

Compiled by the RevenueBase Data Team Data refreshed Aug 31, 2026 4,153 companies tracked

RevenueBase identified 4,153 clean energy consultancy companies headquartered in the United States as of August 2026 and tracks 68,689 professional contacts across them, including 30,790 with verified work emails and 29,271 with mobile numbers. Houston is the largest hub.

This list covers clean energy consultancy companies headquartered in the United States, matched on what each company actually does as described in its own words. Ranked by team size, largest first. Every row shows the company's own description, its RevenueBase Smart Search rating, and when it was last checked. Data refreshed August 31, 2026.

Published by RevenueBase, a B2B data infrastructure company. This list was built with RevenueBase Smart Search, the natural-language company search RevenueBase customers use to build their own targeted lists and unlock verified emails and direct dials at the companies on them. How these lists are built and judged.

How to read this list RevenueBase Smart Search rating on every row Refreshed Aug 31, 2026 86% judged on-target in blind review

4,153Companies

68,689Contacts tracked

30,790Verified emails

29,271Mobile numbers

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The 25 largest clean energy consultancy companies based in the United States

Ranked by team size

Top 25 of 4,153 clean energy consultancy companies based in the United States, ranked by team size, largest first. Data refreshed Aug 31, 2026. RevenueBase Smart Search rates how each company's information relates to clean energy consultancy companies: strong evidence (its own description names it), partial (names part of it), indirect (matched on the rest of its profile rather than the description shown). Click a contact count to view that company's people.
#	Company	RevenueBase Smart Search	Headquarters	Employees	Contacts
1	Sargent & Lundy	Indirect evidence	Midland, TX, United States	1,001-5,000	4,145 contacts →
	Indirect evidence “Sargent & Lundy is one of the world’s longest-standing full-service architect engineering firms.” Source: RevenueBase Database · checked Aug 31, 2026
2	FTI	Partial evidence	Menasha, WI, United States	1,001-5,000	2,712 contacts →
	Partial evidence “Faith Technologies Incorporated (FTI) is a dynamic organization comprised of construction, engineering, manufacturing and renewable energy experts.” Source: RevenueBase Database · checked Aug 31, 2026
3	Langan Engineering & Environmental Services	Indirect evidence	El Segundo, CA, United States	1,001-5,000	2,136 contacts →
	Indirect evidence “Langan's client-focused, highly entrepreneurial culture cultivates an environment of opportunities in which career growth and teamwork flourish.” Source: RevenueBase Database · checked Aug 31, 2026
4	Westwood Professional Services	Indirect evidence	Lake Charles, LA, United States	1,001-5,000	1,631 contacts →
	Indirect evidence “At Westwood, our purpose is to create a better world for people through our work.” Source: RevenueBase Database · checked Aug 31, 2026
5	Swca Environmental Consultants	Indirect evidence	Phoenix, AZ, United States	1,001-5,000	1,618 contacts →
	Indirect evidence “Founded on a commitment to sound science and creative solutions, SWCA is a leader in environmental and management consulting services.” Source: RevenueBase Database · checked Aug 31, 2026
6	Ameresco	Partial evidence	Framingham, MA, United States	1,001-5,000	1,475 contacts →
	Partial evidence “Ameresco, Inc.(NYSE:AMRC) is a leading energy infrastructure solutions provider dedicated to helping customers reduce costs, enhance resilience, and decarbonize to net zero in the…” Source: RevenueBase Database · checked Aug 31, 2026
7	Davey Resource Group, INC	Indirect evidence	Kent, OH, United States	1,001-5,000	1,407 contacts →
	Indirect evidence “We are officially known as Davey Resource Group Inc, but we are more likely to come up in conversation around a successful project we've completed for a client or a capability we…” Source: RevenueBase Database · checked Aug 31, 2026
8	Barr Engineering CO	Indirect evidence	Washington, United States	1,001-5,000	1,098 contacts →
	Indirect evidence “Barr provides engineering and environmental consulting services to clients across the Midwest, throughout the Americas, and around the world.” Source: RevenueBase Database · checked Aug 31, 2026
9	Willdan	Indirect evidence	Anaheim, CA, United States	1,001-5,000	838 contacts →
	Indirect evidence “Willdan (NASDAQ: WLDN) provides professional consulting and technical services to utilities, public agencies and private industry throughout the United States.” Source: RevenueBase Database · checked Aug 31, 2026
10	Energy Solutions	Partial evidence	Orange, CA, United States	201-500	768 contacts →
	Partial evidence “Our mission is simple - to combat climate change through market-based, cost-effective energy, carbon, and water management solutions that make big impacts.” Source: RevenueBase Database · checked Aug 31, 2026
11	Resource Innovations	Partial evidence	Chandler, AZ, United States	501-1,000	724 contacts →
	Partial evidence “Resource Innovations (RI) is an energy transformation firm.” Source: RevenueBase Database · checked Aug 31, 2026
12	Inerco	Indirect evidence	Delaware, United States	1,001-5,000	682 contacts →
	Indirect evidence “INERCO, with 30 years of experience, offers comprehensive services and develops advanced technologies that contribute to sustainable industrial development, acting as a leader in…” Source: RevenueBase Database · checked Aug 31, 2026
13	Tighe & Bond	Indirect evidence	Portland, ME, United States	501-1,000	638 contacts →
	Indirect evidence “Tighe & Bond is the Northeast’s leading engineering, environmental, planning, and design consulting firm.” Source: RevenueBase Database · checked Aug 31, 2026
14	Depcom Power, INC	Partial evidence	Bedminster, NJ, United States	1,001-5,000	623 contacts →
	Partial evidence “DEPCOM Power, a Koch Engineered Solutions Company, is a leading solar energy solutions partner providing Development Support, Engineering, Procurement & Construction (EPC)…” Source: RevenueBase Database · checked Aug 31, 2026
15	XODUS	Strong evidence	Boston, MA, United States	201-500	527 contacts →
	Strong evidence “As a global energy consultancy, we unite our unique and diverse people to share knowledge, innovate and inspire change within the energy industry.” Source: RevenueBase Database · checked Aug 31, 2026
16	Natural Power	Strong evidence	Seattle, WA, United States	501-1,000	505 contacts →
	Strong evidence “Natural Power is a leading independent consultancy and service provider for the renewable energy sector.” Source: RevenueBase Database · checked Aug 31, 2026
17	Hunt Guillot & Associates HGA	Indirect evidence	Ruston, LA, United States	501-1,000	499 contacts →
	Indirect evidence “HGA is a leading engineering, consulting, and program management company that has been delivering innovative and sustainable solutions to our clients for over 29 years.” Source: RevenueBase Database · checked Aug 31, 2026
18	TRIO	Partial evidence	Mclean, VA, United States	201-500	382 contacts →
	Partial evidence “We are Trio – built from Edison Energy, Alfa Energy, and Altenex Energy.” Source: RevenueBase Database · checked Aug 31, 2026
19	Veregy	Partial evidence	Phoenix, AZ, United States	501-1,000	376 contacts →
	Partial evidence “Veregy is an award-winning NAESCO-Accredited decarbonization company focusing on accelerating and simplifying the Energy Transition.” Source: RevenueBase Database · checked Aug 31, 2026
20	Manhard Consulting	Indirect evidence	Fort Worth, TX, United States	201-500	373 contacts →
	Indirect evidence “Manhard Consulting has joined Atwell, a national consulting, engineering, and construction services firm with 2,100 technical professionals across the country.” Source: RevenueBase Database · checked Aug 31, 2026
21	P2s	Indirect evidence	Irvine, CA, United States	201-500	370 contacts →
	Indirect evidence “P2S has brought forward-thinking, sustainable engineering solutions to California, the Pacific Northwest, and beyond, for over 30 years.” Source: RevenueBase Database · checked Aug 31, 2026
22	Takkion	Partial evidence	Evansville, WY, United States	1,001-5,000	360 contacts →
	Partial evidence “TAKKION is Moving Energy Forward.” Source: RevenueBase Database · checked Aug 31, 2026
23	Wendel Companies	Partial evidence	Middletown, CT, United States	201-500	354 contacts →
	Partial evidence “Wendel is an Architecture, Engineering, Energy Efficiency, and Construction Management Firm that delivers customized solutions and turnkey projects in innovative ways.” Source: RevenueBase Database · checked Aug 31, 2026
24	U.S. Energy	Indirect evidence	Houston, TX, United States	1,001-5,000	327 contacts →
	Indirect evidence “U.S.” Source: RevenueBase Database · checked Aug 31, 2026
25	3degrees Group, INC	Indirect evidence	San Francisco, CA, United States	201-500	325 contacts →
	Indirect evidence “3Degrees is a leading global climate solutions provider, pioneer of environmental markets, and Certified B Corporation.” Source: RevenueBase Database · checked Aug 31, 2026

RevenueBase Smart Search

RevenueBase Smart Search assesses information from a company’s LinkedIn profile, information supplied directly by the company, its website, and other publicly available sources. It uses that information to rate how closely the company relates to this list’s category: clean energy consultancy companies. Every row carries its rating and the description the rating was read from, so each one can be checked rather than taken on trust.

Strong evidence: The company's own public description of its business names clean energy consultancy companies.
Partial evidence: Its own public description names part of clean energy consultancy companies, so it works in or next to the category without describing itself that way.
Indirect evidence: The description shown does not name clean energy consultancy companies. The match rests on the rest of the company's public profile rather than the one sentence quoted here, so this is the rating to check first.

RevenueBase Smart Search is how these lists are built: RevenueBase's data engine and AI assemble the companies that match a category defined in a user's own words, so a list can be about what companies actually do rather than about whichever industry code they were filed under.

Showing 25 of 4,153 clean energy consultancy companies based in the United States

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Clean energy consultancy companies based in the United States at a glance

As of Aug 31, 2026

44.8%Verified-email coverage

42.6%Mobile-number coverage

16.5Average contacts per company

1-10Median size (employees)

4.3%Largest-city concentration · Houston

Aug 31, 2026Page data refreshed

Companies by employee count

1-10

2,563

11-50

1,119

51-200

330

201-500

501-1,000

1,001-5,000

5,001-10,000

How this list was built

Company categories are rarely black and white. RevenueBase reads each company's own description of its business to decide whether it belongs among clean energy consultancy companies, so some rows will be adjacent to the category rather than pure plays. The description and RevenueBase Smart Search rating on every row are there so you can check each match yourself.

Source: The RevenueBase company graph: 60 million companies and 398.9 million professional contacts resolved from primary sources, queried with RevenueBase Smart Search, the natural-language company search available to every RevenueBase user.
What qualifies: Companies headquartered in the United States whose own description of what they do matches “clean energy consultancy companies”. Matching reads each company's description, not its industry code or its name.
RevenueBase Smart Search: RevenueBase Smart Search is how this list is assembled and how each row is rated. RevenueBase's data engine and AI assess a company's LinkedIn profile, information supplied directly by the company, its website and other publicly available information, then relate it to a category defined in a user's own words. Each row is rated strong evidence (its own description names clean energy consultancy companies), partial evidence (it names part of the category) or indirect evidence (the description shown names none of it and the match rests on the rest of the company's profile). The description supporting each rating is quoted on the row.
What we exclude: Companies whose own description does not clearly place them among clean energy consultancy companies, and records with no verified work email. Companies headquartered outside United States are excluded even when they keep an office there.
Match quality: In blind human judging of this matching method, 86% of matched companies were on target. Expect roughly 1 in 7 rows to be adjacent to the category rather than a pure play. Every row shows the company's own description and its RevenueBase Smart Search rating so you can judge each match yourself. Read the full methodology: how the lists are built, how the judging worked, and what the figure means.
Ranking: Team size, largest first: companies are ordered by the number of professionals RevenueBase tracks at each one. Employee ranges shown are reported bands, for context.
Verification: Every listed company carries at least one verified work email, 30,790 across the full list. Contacts re-verify on a rolling cadence, and each contact's own verification date is shown inside RevenueBase.
Refresh: This page's figures were pulled from the company graph on August 31, 2026. Lists refresh periodically as the graph is re-checked.
Corrections: Wrong category, wrong headquarters, or a company that has closed? Use “Report an issue” on any row. Reports go to the RevenueBase Data Team and feed back into the company graph.

Clean energy consultancy companies by metro

Frequently asked

What is RevenueBase Smart Search?

RevenueBase Smart Search is how RevenueBase decides which companies belong on this list and how strongly each one fits. Its data engine and AI assess a company's LinkedIn profile, information supplied directly by the company, its website and other publicly available information, then relate it to the category the list is about. Each row is rated strong evidence when the company's own description names clean energy consultancy companies, partial evidence when it names part of the category, and indirect evidence when the description shown names none of it and the match rests on the rest of the company's profile.

How many clean energy consultancy companies are there based in the United States?

RevenueBase identified 4,153 clean energy consultancy companies headquartered in the United States as of August 2026, matched on each company's own description of what it does rather than its industry code.

What is the largest company on this list?

Sargent & Lundy, headquartered in Midland, tops this list with the largest team on record.

Which city has the most clean energy consultancy companies?

Houston leads with 178 headquartered companies, followed by New York (168) and Washington (97).

How do I get contact information for these companies?

A free RevenueBase account lets you run this exact search and work the top results, verified emails and direct dials included. Upgrading unlocks all 30,790 verified decision-maker contacts tracked across these 4,153 companies.

How current is this list?

The list refreshes periodically as the company graph is re-checked. This page's figures were pulled on August 31, 2026.

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About this data

RevenueBase is a B2B data infrastructure company. Its company graph covers 60 million companies and 398.9 million professional contacts, with emails verified on a rolling cadence rather than scraped once and left to decay. These company lists are generated directly from that graph with RevenueBase Smart Search, the same natural-language company search every RevenueBase user has: describe a market in plain words, get the companies that match, and add verified emails and direct dials for the people at them. It is the same data that powers RevenueBase's B2B data products, and a free account includes 500 credits to start. How these lists are built and judged.