Company lists · Data refreshed September 2026

Top 25 Cleantech consulting firms based in the United States

Name: Cleantech consulting firms based in the United States
Creator: RevenueBase
License: https://creativecommons.org/licenses/by/4.0/

Compiled by the RevenueBase Data Team Data refreshed Sep 21, 2026 1,593 companies tracked

RevenueBase identified 1,593 cleantech consulting firms headquartered in the United States as of September 2026 and tracks 16,296 professional contacts across them, including 7,628 with verified work emails. Houston is the largest hub.

This list covers cleantech consulting firms 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 21, 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 21, 2026 86% judged on-target in blind review

1,593Companies

16,296Contacts tracked

7,628Verified emails

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The 25 largest cleantech consulting firms based in the United States

Ranked by team size

Top 25 of 1,593 cleantech consulting firms based in the United States, ranked by team size, largest first. Data refreshed Sep 21, 2026. RevenueBase Smart Search rates how each company's information relates to cleantech consulting firms: 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	Montrose Environmental Group	Indirect evidence	Little Rock, AR, United StatesHQ checked Sep 21, 2026	1,001-5,000	1,529 contacts →
	Indirect evidence “Onterris (formerly Montrose Environmental Group) was one of the first to see environmental responsibility as not just an imperative but as a strategic asset.” Source: RevenueBase Database · checked Sep 21, 2026
2	Willdan	Partial evidence	Anaheim, CA, United StatesHQ checked Sep 21, 2026	1,001-5,000	851 contacts →
	Partial 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 21, 2026
3	TRIO	Indirect evidence	Irvine, CA, United StatesHQ checked Sep 21, 2026	201-500	383 contacts →
	Indirect evidence “We are Trio – built from Edison Energy, Alfa Energy, and Altenex Energy.” Source: RevenueBase Database · checked Sep 21, 2026
4	P2s	Indirect evidence	Long Beach, CA, United StatesHQ checked Sep 21, 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 21, 2026
5	Environmental Consulting & Technology, Inc. ECT	Partial evidence	Gainesville, FL, United StatesHQ checked Sep 21, 2026	201-500	305 contacts →
	Partial 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 21, 2026
6	Cascade Energy	Indirect evidence	Portland, OR, United StatesHQ checked Sep 21, 2026	201-500	288 contacts →
	Indirect evidence “At Cascade Energy, we believe in better.” Source: RevenueBase Database · checked Sep 21, 2026
7	Merjent	Partial evidence	Minneapolis, MN, United StatesHQ checked Sep 21, 2026	201-500	264 contacts →
	Partial evidence “Merjent is an environmental, restoration, and engineering consulting firm with a long history serving the energy industry.” Source: RevenueBase Database · checked Sep 21, 2026
8	PSC Consulting	Partial evidence	Kirkland, WA, United StatesHQ checked Sep 21, 2026	201-500	254 contacts →
	Partial evidence “We provide global renewable energy consulting services, focused on empowering clients to navigate the complexities of the energy transition.” Source: RevenueBase Database · checked Sep 21, 2026
9	PEG	Indirect evidence	Fairfax, VA, United StatesHQ checked Sep 21, 2026	201-500	214 contacts →
	Indirect evidence “PEG presents a comprehensive capacity for the evaluation and understanding of a broad base of energy and environmental sustainability related programs, policies and initiatives.” Source: RevenueBase Database · checked Sep 21, 2026
10	Frontier Energy, INC	Indirect evidence	Pleasanton, CA, United StatesHQ checked Sep 21, 2026	51-200	192 contacts →
	Indirect evidence “Frontier Energy is a professional services firm that excels in market transformation.” Source: RevenueBase Database · checked Sep 21, 2026
11	Nexant	Partial evidence	Half Moon Bay, CA, United StatesHQ checked Sep 21, 2026	201-500	183 contacts →
	Partial evidence “Resource Innovations now combined with Nexant is a substantially woman-owned, woman-led energy consulting firm dedicated to creating equal access to clean resources through…” Source: RevenueBase Database · checked Sep 21, 2026
12	Green World Renewable Energy LLC	Indirect evidence	Brooklyn, MD, United StatesHQ checked Sep 21, 2026	201-500	182 contacts →
	Indirect evidence “Green World Renewable Energy delivers smart, scalable solar engineering and back-office design solutions for residential, commercial, and utility-scale projects across the U.S.” Source: RevenueBase Database · checked Sep 21, 2026
13	Utilicast	Partial evidence	Seattle, WA, United StatesHQ checked Sep 21, 2026	201-500	181 contacts →
	Partial evidence “Utilicast is more than just a consulting company.” Source: RevenueBase Database · checked Sep 21, 2026
14	Terraphase Engineering INC	Indirect evidence	Oakland, CA, United StatesHQ checked Sep 21, 2026	201-500	166 contacts →
	Indirect evidence “Terraphase offers cost-effective solutions to complex environmental and engineering challenges.” Source: RevenueBase Database · checked Sep 21, 2026
15	Marathon Capital	Indirect evidence	Chicago, IL, United StatesHQ checked Sep 21, 2026	51-200	163 contacts →
	Indirect evidence “Marathon Capital is the largest independent investment bank dedicated to servicing the clean economy.” Source: RevenueBase Database · checked Sep 21, 2026
16	Energy And Environmental Economics, INC	Indirect evidence	San Francisco, CA, United StatesHQ checked Sep 21, 2026	51-200	156 contacts →
	Indirect evidence “Energy.” Source: RevenueBase Database · checked Sep 21, 2026
17	Energetics	Partial evidence	Columbia, MD, United StatesHQ checked Sep 21, 2026	51-200	150 contacts →
	Partial evidence “Energetics is a full-service technical and management consulting company specializing in energy (specifically energy modernization, efficiency, and clean energy) and…” Source: RevenueBase Database · checked Sep 21, 2026
18	Four Seasons Environmental, INC	Indirect evidence	Monroe, OH, United StatesHQ checked Sep 21, 2026	201-500	134 contacts →
	Indirect evidence Source: RevenueBase Database · checked Sep 21, 2026
19	Cleantech Open	Partial evidence	Los Angeles, CA, United StatesHQ checked Sep 21, 2026	11-50	132 contacts →
	Partial evidence “The Cleantech Open runs the world's largest cleantech accelerator.” Source: RevenueBase Database · checked Sep 21, 2026
20	Luzco Technologies LLC	Indirect evidence	St. Louis, MO, United StatesHQ checked Sep 21, 2026	51-200	126 contacts →
	Indirect evidence “LUZCO’s team of knowledgeable experts will strategically guide your team through each step of the process and help you develop innovative strategies, improve efficiency, enhance…” Source: RevenueBase Database · checked Sep 21, 2026
21	Halker	Partial evidence	Centennial, CO, United StatesHQ checked Sep 21, 2026	51-200	121 contacts →
	Partial evidence “Halker Consulting provides custom engineered and configured services in Project Assessment and Planning, Engineering and Design, & Consulting and Implementation Guidance.” Source: RevenueBase Database · checked Sep 21, 2026
22	Michaels Energy- An Inc. 5000 Company	Partial evidence	La Crosse, WI, United StatesHQ checked Sep 21, 2026	51-200	121 contacts →
	Partial evidence “Michaels Energy is a veteran-owned energy consulting firm that exists to help businesses minimize waste and maximize value.” Source: RevenueBase Database · checked Sep 21, 2026
23	Envocore	Indirect evidence	Gambrills, MD, United StatesHQ checked Sep 21, 2026	201-500	116 contacts →
	Indirect evidence “We make sustainable happen.” Source: RevenueBase Database · checked Sep 21, 2026
24	Cascadia Consulting Group	Partial evidence	Seattle, WA, United StatesHQ checked Sep 21, 2026	51-200	110 contacts →
	Partial evidence “Cascadia Consulting Group is a majority women-owned consulting firm specializing in environmental and sustainability solutions.” Source: RevenueBase Database · checked Sep 21, 2026
25	Cleantech Group	Indirect evidence	San Francisco, CA, United StatesHQ checked Sep 21, 2026	11-50	110 contacts →
	Indirect evidence “Winning in clean technologies is complex-new technologies emerge, policies shift, and it’s hard to know which opportunities will scale and which will fail.” Source: RevenueBase Database · checked Sep 21, 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: cleantech consulting firms. 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 cleantech consulting firms.
Partial evidence: Its own public description names part of cleantech consulting firms, so it works in or next to the category without describing itself that way.
Indirect evidence: The description shown does not name cleantech consulting firms. 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 1,593 cleantech consulting firms based in the United States

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Cleantech consulting firms based in the United States at a glance

As of Sep 21, 2026

46.8%Verified-email coverage

10.2Average contacts per company

1-10Median size (employees)

3.8%Largest-city concentration · Houston

Sep 21, 2026Page data refreshed

Companies by employee count

1-10

1,127

11-50

358

51-200

201-500

501-1,000

1,001-5,000

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 1,593 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 cleantech consulting firms, 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 “cleantech consulting firms”. 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 cleantech consulting firms), 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 cleantech consulting firms, 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, 7,628 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 21, 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.

Cleantech consulting firms 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 cleantech consulting firms, 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 cleantech consulting firms are there based in the United States?

RevenueBase identified 1,593 cleantech consulting firms 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?

Montrose Environmental Group, headquartered in Little Rock, tops this list with the largest team on record.

Which city has the most cleantech consulting firms?

Houston leads with 60 headquartered companies, followed by New York (59) and Washington (53).

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 7,628 verified decision-maker contacts tracked across these 1,593 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 21, 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.