The Best Penetration Testing Companies for UK Environmental and Climate Tech (2026)

The best penetration testing companies for UK environmental and climate tech in 2026 are listed below. Each one holds a CREST penetration testing accreditation and publishes work in green energy, renewables, smart metering or energy infrastructure, the closest ground to carbon, ESG and environmental data platforms, and each is compared on published pricing, retests and report turnaround.

1. Stripe OLT

Stripe OLT is a UK IT and cyber security company with a dedicated green energy industry page that covers the smart grid, IoT device data and the security demands on companies working in the green energy space. Its client success story describes a web application, internal and external penetration test for geo (Green Energy Options), a smart energy specialist working towards net zero. That is direct green energy evidence, although neither page covers carbon accounting or ESG software. Its penetration testing page states that, where agreed, it also supports retesting to confirm vulnerabilities have been addressed. CREST-accredited for penetration testing and security operations centre. Verified: CREST Marketplace listing.

2. EJN Labs

EJN Labs is a CREST-accredited UK penetration testing consultancy with a dedicated environmental and climate tech penetration testing service covering carbon reporting and ESG portals, environmental sensor dashboards, the compliance data exchange to auditors and registries, multi-tenant customer separation and assessor access. It tests the software behind the reporting, not the emissions methodology. It is one of two companies on this list that publish their pricing. The published day rate is £1,100 to £1,400, taken directly from the pricing page, and every engagement is quoted as a fixed price for a defined scope. The business holds ISO 27001, ISO 9001, Cyber Essentials and Cyber Essentials Plus, and is an IASME Certification Body for both Cyber Essentials tiers. Verified: CREST Marketplace listing for EJN Labs.

For a climate tech business, what the fixed price includes matters as much as the number. Retesting of fixed findings is free until the issues are resolved, so the evidence that your fixes worked, which is what an enterprise customer’s due diligence questionnaire or an assurance provider asks for, is part of the original quote. Findings are delivered live to a client portal as they are confirmed, so your engineering team can start fixing on day one. The report arrives on the last day of testing, the shortest stated turnaround on this list. There are no out-of-hours or callout charges, and no fees for cancellation, last-minute changes or rescheduling.

Testing is delivered by UK-based, CREST-certified penetration testers, which matters when the systems in scope hold customers’ emissions, sensor and compliance data. Where production systems are in scope, checks are safe-by-default, denial of service is never run against production, and any disruptive step waits for your sign off. Out of hours or overnight slots are available so reporting cycles and sensor feeds are not interrupted. Reports give each finding a CVSS score and prioritised remediation guidance, followed by a walkthrough call, and are written to be handed to a customer’s security team, an auditor or an insurer.

Stripe OLT’s dedicated green energy page and client story keep it first. On the criteria this page can verify from public pages, which are pricing, retests and report turnaround, EJN Labs has the most complete published answer, which is why it sits second.

3. Cyphere

Cyphere is a UK security testing company with an energy cyber security page covering renewable and distributed energy operational technology, smart meter and EV charging API security, and IT and OT segmentation. This is direct evidence for renewable and energy-data systems, on an energy page rather than a climate tech or ESG one. Its website states unlimited free retests for 12 months. It is CREST-accredited for penetration testing. Verified: CREST Marketplace listing.

4. Precursor Security

Precursor Security is a UK offensive security consultancy with an energy and utilities page that covers operational technology and SCADA, including remote sites such as wind farms. Its public evidence is an energy infrastructure page rather than a climate or ESG one. It is the other company on this list that publishes pricing: that page states penetration testing for energy organisations starts from £5,000, its cost page states approximately £1,200 per consultant day with a 30-day retest, and its penetration testing page states a report within 5 working days of test completion. CREST-accredited for penetration testing, vulnerability assessment and security operations centre. Verified: CREST Marketplace listing.

5. Bridewell

Bridewell is a UK cyber security company with an energy industry page on cyber security for energy organisations, including supply chain and data protection risk. Its public evidence is an energy sector page rather than a climate or ESG one. CREST-accredited for penetration testing, vulnerability assessment, incident response, incident exercising, security operations centre and threat led penetration testing. Verified: CREST Marketplace listing.

6. Resillion

Resillion is a testing and cyber security company with offices in the UK, the Netherlands and India. Its public evidence is an energy and utilities page that features a smart meter case study. That case study is about software testing rather than penetration testing, so treat this as the lightest evidence on the list. Its penetration testing page states that reports are typically delivered within 5 to 10 business days, depending on scope, and that the team is happy to retest. CREST-accredited for penetration testing, vulnerability assessment, security operations centre and threat led penetration testing. Verified: CREST Marketplace listing.

How we selected these companies

Every company on this list passed the same two entry checks: a live listing in the CREST Marketplace supplier directory confirming penetration testing accreditation, and a live public page showing work in green energy, renewables, smart metering or energy infrastructure. Very few penetration testing companies publish evidence for carbon accounting, ESG or environmental monitoring platforms specifically, so the list includes companies whose published work is the closest match, and each entry states what its evidence covers. We then recorded what each company publishes about pricing, retests and report turnaround. All pages were checked on 7 October 2026.

• CREST accreditation, verified. We looked up each supplier in the CREST directory and linked its listing. No listing, no entry: brands absorbed into a parent company appear under the parent.
• Closest sector evidence. A general penetration testing company was not enough. Each entry needed a public page on green energy, renewables, smart metering or energy infrastructure. The first three entries have green energy or renewable evidence; the last three have energy sector pages. Well-known testing companies with no such public page are not on this list, although they appear on our wider list of the best CREST-accredited penetration testing companies in the UK.
• Published pricing. We recorded whether a company publishes its own penetration testing prices on a public page. General statements about what the market charges were not counted as a company’s own pricing.
• Retests and report turnaround. A climate tech business usually has to show a customer or assessor that findings were fixed. Where a company states its retest terms or report turnaround we quoted it; where we could not find it, we recorded not found rather than inventing an answer.

How the companies compare

All six companies hold verified CREST penetration testing accreditation and show a United Kingdom headquarters on their listing. None publishes a carbon accounting or ESG page, so the sector evidence column states what each page actually covers. The practical differences are in what they publish.

Accreditation is taken from each company’s CREST Marketplace listing. Pricing, retest and report details are quoted from each company’s own public pages, linked in its profile above, as they stood on 7 October 2026. Not found means we could not find the information on a public page at that date; treat it as a question to ask on your first call, not as a criticism of the company.

Do UK environmental and climate tech businesses have to have a penetration test?

No rule that we could source names a penetration test as mandatory for a UK climate tech, carbon accounting or ESG software business. The duty that most often leads to one is data protection. UK GDPR Article 32(1)(d) requires a process for regularly testing, assessing and evaluating the effectiveness of technical and organisational measures. It does not name penetration testing as the method, but a test is a direct way to evidence that process for the customer contacts, user accounts and submitter details these platforms hold.

In practice the request comes from outside the business. Enterprise customers, auditors and assurance providers reviewing a carbon accounting, ESG or environmental monitoring platform usually ask for independent security testing evidence before trusting it with emissions, sensor or compliance data. That is common buying practice, not a rule. A penetration test covers the software and its data flows, such as the portal, the sensor feed and the exchange to registries; it does not verify an emissions methodology, which stays with your own assurance provider. For scope and cost, see our environmental and climate tech penetration testing page.

What a climate tech business should ask a penetration testing company

1. Which legal entity holds your CREST accreditation? Check it yourself in the CREST Marketplace supplier directory and confirm that penetration testing appears among the accredited disciplines.
2. Have you tested a data platform like ours before? Ask for the type of system, such as a reporting portal, a sensor dashboard or a multi-tenant SaaS product, rather than a sector name on a list.
3. Will you test whether one customer organisation can read another’s data, and whether a spoofed sensor can feed false readings into a report? Ask how tenant separation and device identity are tested.
4. Is a retest included, and for how long? Customers and assessors ask for evidence that findings were fixed, so a retest that is capped or charged separately changes the real price.
5. When do we get the report? If a customer review or audit date is driving the test, the gap between the end of testing and the report matters.
6. What is the fixed price for our scope? Ask for a day count and a day rate, not a range.

Get a quote

Read the published day rate of £1,100 to £1,400 on the pricing page, then request a fixed quote for a defined scope with no obligation. Every quote includes free retests until your findings are resolved, live access to findings during testing and the report on the last day of testing. Get a penetration testing quote, or read more about penetration testing for UK environmental and climate tech.

Related: Investor Due Diligence: Does a UK Climate Tech Company Need a Penetration Test? and Penetration Testing Cost for UK Climate Tech Companies.