Company lists · Data refreshed September 2026

Top 25 Sustainable energy consulting firms based in the United States

RevenueBase identified 4,055 sustainable energy consulting firms headquartered in the United States as of September 2026 and tracks 60,310 professional contacts across them, including 27,901 with verified work emails. New York is the largest hub.

This list covers sustainable energy 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
4,055Companies
60,310Contacts tracked
27,901Verified emails
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The 25 largest sustainable energy consulting firms based in the United States

Ranked by team size
Top 25 of 4,055 sustainable energy 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 sustainable energy 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.
#CompanyRevenueBase Smart SearchHeadquartersEmployeesContacts
1Partial evidenceMenasha, WI, United StatesHQ checked Sep 21, 20261,001-5,0002,741 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 21, 2026
2Indirect evidenceBaton Rouge, LA, United StatesHQ checked Sep 21, 20261,001-5,0002,639 contacts →

Indirect evidence

“APTIM enhances the quality of the environment, wellbeing of people, resilience of communities, and opportunity for employees to make a difference, not just a living.”

Source: RevenueBase Database · checked Sep 21, 2026
3Partial evidenceSeattle, WA, United StatesHQ checked Sep 21, 20261,001-5,0002,213 contacts →

Partial evidence

“We're a national construction and energy services company dedicated to innovating the waste and climate harm out of the built environment.”

Source: RevenueBase Database · checked Sep 21, 2026
4Strong evidenceAustin, TX, United StatesHQ checked Sep 21, 20261,001-5,0002,121 contacts →

Strong evidence

“CLEAResult is the largest provider of energy efficiency, energy transition and energy sustainability services in North America.”

Source: RevenueBase Database · checked Sep 21, 2026
5Indirect evidencePlano, TX, United StatesHQ checked Sep 21, 20261,001-5,0001,661 contacts →

Indirect evidence

“At Westwood, our purpose is to create a better world for people through our work.”

Source: RevenueBase Database · checked Sep 21, 2026
6Partial evidencePhoenix, AZ, United StatesHQ checked Sep 21, 20261,001-5,0001,629 contacts →

Partial 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 Sep 21, 2026
7Partial evidenceFramingham, MA, United StatesHQ checked Sep 21, 20261,001-5,0001,383 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 21, 2026
8Strong evidenceAustin, TX, United StatesHQ checked Sep 21, 2026n/a1,145 contacts →

Strong 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 21, 2026
9Partial evidenceAnaheim, CA, United StatesHQ checked Sep 21, 20261,001-5,000851 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
10Partial evidenceOakland, CA, United StatesHQ checked Sep 21, 2026201-500772 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 21, 2026
11Partial evidencePortland, OR, United StatesHQ checked Sep 21, 2026201-500744 contacts →

Partial evidence

“PAE provides mechanical and electrical engineering design, technology system design, energy modeling and analysis, and more.”

Source: RevenueBase Database · checked Sep 21, 2026
12Partial evidenceHalf Moon Bay, CA, United StatesHQ checked Sep 21, 2026501-1,000733 contacts →

Partial evidence

“Resource Innovations (RI) is an energy transformation firm.”

Source: RevenueBase Database · checked Sep 21, 2026
13Partial evidenceSt Paul, MN, United StatesHQ checked Sep 21, 20261,001-5,000658 contacts →

Partial evidence

“Antea Group is an international engineering and environmental consulting firm specializing in full-service solutions in the fields of environment, health and safety, and…”

Source: RevenueBase Database · checked Sep 21, 2026
14Indirect evidenceWilmington, DE, United StatesHQ checked Sep 21, 202610001+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 21, 2026
15Partial evidenceWashington, DC, United StatesHQ checked Sep 21, 202651-200434 contacts →

Partial evidence

“Synergy Consulting is Global Leader in Financial and Corporate Advisory.”

Source: RevenueBase Database · checked Sep 21, 2026
16Indirect evidenceSan Francisco, CA, United StatesHQ checked Sep 21, 2026201-500386 contacts →

Indirect evidence

“Glumac, a Tetra Tech Company, is a global leader in building engineering, committed to delivering a low carbon future for all.”

Source: RevenueBase Database · checked Sep 21, 2026
17Partial evidenceIrvine, CA, United StatesHQ checked Sep 21, 2026201-500383 contacts →

Partial evidence

“We are Trio – built from Edison Energy, Alfa Energy, and Altenex Energy.”

Source: RevenueBase Database · checked Sep 21, 2026
18Indirect evidenceDenver, United StatesHQ checked Sep 21, 2026501-1,000379 contacts →

Indirect evidence

“Established in 2019.”

Source: RevenueBase Database · checked Sep 21, 2026
19Partial evidenceLong Beach, CA, United StatesHQ checked Sep 21, 2026201-500375 contacts →

Partial 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
20Partial evidenceEvansville, WY, United StatesHQ checked Sep 21, 20261,001-5,000358 contacts →

Partial evidence

“TAKKION is Moving Energy Forward.”

Source: RevenueBase Database · checked Sep 21, 2026
21Partial evidenceWilliamsville, NY, United StatesHQ checked Sep 21, 2026201-500355 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 21, 2026
22Indirect evidencePark Ridge, NJ, United StatesHQ checked Sep 21, 2026201-500336 contacts →

Indirect evidence

“National Utility Service, Inc.”

Source: RevenueBase Database · checked Sep 21, 2026
23Strong evidenceGainesville, FL, United StatesHQ checked Sep 21, 2026201-500305 contacts →

Strong 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
24Partial evidenceJackson, MI, United StatesHQ checked Sep 21, 2026201-500305 contacts →

Partial evidence

“We provide expert engineering and consulting services that enable a more reliable and resilient power system.”

Source: RevenueBase Database · checked Sep 21, 2026
25Indirect evidenceBaton Rouge, LA, United StatesHQ checked Sep 21, 202651-200305 contacts →

Indirect evidence

“CSRS was acquired by Westwood Professional Services on June 30, 2025.”

Source: RevenueBase Database · checked Sep 21, 2026

Showing 25 of 4,055 sustainable energy consulting firms based in the United States

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Sustainable energy consulting firms based in the United States at a glance

As of Sep 21, 2026
46.3%Verified-email coverage
14.9Average contacts per company
1-10Median size (employees)
4.1%Largest-city concentration · New York
Sep 21, 2026Page data refreshed

Companies by employee count

1-10
2,635
11-50
1,030
51-200
277
201-500
59
501-1,000
10
1,001-5,000
28
5,001-10,000
2
10001+
2

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 4,055 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 sustainable energy 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 “sustainable energy 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 sustainable energy 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 sustainable energy 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, 27,901 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.

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 sustainable energy 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 sustainable energy consulting firms are there based in the United States?

RevenueBase identified 4,055 sustainable energy 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?

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

Which city has the most sustainable energy consulting firms?

New York leads with 168 headquartered companies, followed by Houston (165) and Chicago (91).

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 27,901 verified decision-maker contacts tracked across these 4,055 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.