Company lists · Data refreshed September 2026

Top 25 Clean energy consultants based in the United States

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

Compiled by the RevenueBase Data Team Data refreshed Sep 16, 2026 3,383 companies tracked

RevenueBase identified 3,383 clean energy consultants headquartered in the United States as of September 2026 and tracks 53,246 professional contacts across them, including 24,392 with verified work emails. Houston is the largest hub.

This list covers clean energy consultants 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 September 16, 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 HQ checked on every row RevenueBase Smart Search rating on every row Refreshed Sep 16, 2026 86% judged on-target in blind review

3,383Companies

53,246Contacts tracked

24,392Verified emails

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The 25 largest clean energy consultants based in the United States

Ranked by team size

Top 25 of 3,383 clean energy consultants based in the United States, ranked by team size, largest first. Data refreshed Sep 16, 2026. RevenueBase Smart Search rates how each company's information relates to clean energy consultants: 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	FTI	Partial evidence	Menasha, WI, United StatesHQ checked Sep 16, 2026	1,001-5,000	2,741 contacts →
	Partial evidence “Faith Technologies Incorporated (FTI) is a dynamic organization comprised of construction, engineering, manufacturing and renewable energy experts.” Source: RevenueBase Database · checked Sep 16, 2026
2	Langan Engineering & Environmental Services	Indirect evidence	Parsippany, NJ, United StatesHQ checked Sep 16, 2026	1,001-5,000	2,177 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 Sep 16, 2026
3	Clearesult	Partial evidence	Austin, TX, United StatesHQ checked Sep 16, 2026	1,001-5,000	2,121 contacts →
	Partial evidence “CLEAResult is the largest provider of energy efficiency, energy transition and energy sustainability services in North America.” Source: RevenueBase Database · checked Sep 16, 2026
4	Westwood Professional Services	Indirect evidence	Plano, TX, United StatesHQ checked Sep 16, 2026	1,001-5,000	1,661 contacts →
	Indirect evidence “At Westwood, our purpose is to create a better world for people through our work.” Source: RevenueBase Database · checked Sep 16, 2026
5	Ameresco	Partial evidence	Framingham, MA, United StatesHQ checked Sep 16, 2026	1,001-5,000	1,383 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 Sep 16, 2026
6	OLA	Indirect evidence	Austin, TX, United StatesHQ checked Sep 16, 2026	n/a	1,145 contacts →
	Indirect evidence “OLA Sustainability, LLC OLA Sustainability is a consulting firm that focuses on integrating sustainable practices into commercial and multifamily design projects.” Source: RevenueBase Database · checked Sep 16, 2026
7	Barr Engineering CO	Indirect evidence	Minneapolis, MN, United StatesHQ checked Sep 16, 2026	1,001-5,000	1,088 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 Sep 16, 2026
8	Wanzek Construction, Inc., A Mastec Company	Strong evidence	Fargo, ND, United StatesHQ checked Sep 16, 2026	1,001-5,000	933 contacts →
	Strong evidence “Wanzek Construction, Inc, a MasTec Renewables company, is a leading general construction contractor and clean energy services company headquartered in Fargo, North Dakota.” Source: RevenueBase Database · checked Sep 16, 2026
9	Willdan	Indirect evidence	Anaheim, CA, United StatesHQ checked Sep 16, 2026	1,001-5,000	851 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 Sep 16, 2026
10	Energy Solutions	Partial evidence	Oakland, CA, United StatesHQ checked Sep 16, 2026	201-500	772 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 Sep 16, 2026
11	Resource Innovations	Partial evidence	Half Moon Bay, CA, United StatesHQ checked Sep 16, 2026	501-1,000	733 contacts →
	Partial evidence “Resource Innovations (RI) is an energy transformation firm.” Source: RevenueBase Database · checked Sep 16, 2026
12	Depcom Power, INC	Partial evidence	Scottsdale, AZ, United StatesHQ checked Sep 16, 2026	1,001-5,000	624 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 Sep 16, 2026
13	Dupont Water Solutions	Indirect evidence	Wilmington, DE, United StatesHQ checked Sep 16, 2026	10001+	470 contacts →
	Indirect evidence “We’re helping companies in every industry, in every corner of the globe make real progress.” Source: RevenueBase Database · checked Sep 16, 2026
14	Synergy Consulting, INC	Indirect evidence	Washington, DC, United StatesHQ checked Sep 16, 2026	51-200	434 contacts →
	Indirect evidence “Synergy Consulting is Global Leader in Financial and Corporate Advisory.” Source: RevenueBase Database · checked Sep 16, 2026
15	Veregy	Partial evidence	Phoenix, MO, United StatesHQ checked Sep 16, 2026	501-1,000	383 contacts →
	Partial evidence “Veregy is an award-winning NAESCO-Accredited decarbonization company focusing on accelerating and simplifying the Energy Transition.” Source: RevenueBase Database · checked Sep 16, 2026
16	TRIO	Partial evidence	Irvine, CA, United StatesHQ checked Sep 16, 2026	201-500	383 contacts →
	Partial evidence “We are Trio – built from Edison Energy, Alfa Energy, and Altenex Energy.” Source: RevenueBase Database · checked Sep 16, 2026
17	Energyscape Renewables	Indirect evidence	Denver, United StatesHQ checked Sep 16, 2026	501-1,000	379 contacts →
	Indirect evidence “Established in 2019.” Source: RevenueBase Database · checked Sep 16, 2026
18	P2s	Indirect evidence	Long Beach, CA, United StatesHQ checked Sep 16, 2026	201-500	375 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 Sep 16, 2026
19	Manhard Consulting	Indirect evidence	Lincolnshire, IL, United StatesHQ checked Sep 16, 2026	201-500	365 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 Sep 16, 2026
20	Takkion	Partial evidence	Evansville, WY, United StatesHQ checked Sep 16, 2026	1,001-5,000	358 contacts →
	Partial evidence “TAKKION is Moving Energy Forward.” Source: RevenueBase Database · checked Sep 16, 2026
21	Wendel Companies	Partial evidence	Williamsville, NY, United StatesHQ checked Sep 16, 2026	201-500	355 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 Sep 16, 2026
22	NUS Consulting Group	Indirect evidence	Park Ridge, NJ, United StatesHQ checked Sep 16, 2026	201-500	336 contacts →
	Indirect evidence “National Utility Service, Inc.” Source: RevenueBase Database · checked Sep 16, 2026
23	Environmental Consulting & Technology, Inc. ECT	Indirect evidence	Gainesville, FL, United StatesHQ checked Sep 16, 2026	201-500	305 contacts →
	Indirect evidence “Environmental Consulting & Technology, Inc.(ECT) is a multi-disciplinary environmental and sustainability consulting firm delivering strategy, permitting, design, and management…” Source: RevenueBase Database · checked Sep 16, 2026
24	Csrs, A Westwood Company	Indirect evidence	Baton Rouge, LA, United StatesHQ checked Sep 16, 2026	51-200	305 contacts →
	Indirect evidence “CSRS was acquired by Westwood Professional Services on June 30, 2025.” Source: RevenueBase Database · checked Sep 16, 2026
25	Cascade Energy	Partial evidence	Portland, OR, United StatesHQ checked Sep 16, 2026	201-500	288 contacts →
	Partial evidence “At Cascade Energy, we believe in better.” Source: RevenueBase Database · checked Sep 16, 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 consultants. 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 consultants.
Partial evidence: Its own public description names part of clean energy consultants, so it works in or next to the category without describing itself that way.
Indirect evidence: The description shown does not name clean energy consultants. 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 3,383 clean energy consultants based in the United States

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Clean energy consultants based in the United States at a glance

As of Sep 16, 2026

45.8%Verified-email coverage

15.7Average contacts per company

1-10Median size (employees)

3.7%Largest-city concentration · Houston

Sep 16, 2026Page data refreshed

Companies by employee count

1-10

2,025

11-50

978

51-200

275

201-500

501-1,000

1,001-5,000

5,001-10,000

10001+

Email recency for this list is measured worldwide rather than for United States, so it is reported there. Company counts and contact totals on this page are exact for United States, over 3,383 companies.

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 consultants, 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 consultants”. 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 consultants), 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 consultants, 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, 24,392 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 September 16, 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 consultants 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 consultants, 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 consultants are there based in the United States?

RevenueBase identified 3,383 clean energy consultants headquartered in the United States as of September 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?

FTI, headquartered in Menasha, tops this list with the largest team on record.

Which city has the most clean energy consultants?

Houston leads with 125 headquartered companies, followed by New York (115) and Washington (73).

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 24,392 verified decision-maker contacts tracked across these 3,383 companies.

How current is this list?

The list refreshes periodically as the company graph is re-checked. This page's figures were pulled on September 16, 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.