The Best Penetration Testing Companies for UK Energy and Renewables (2026)

The best penetration testing companies for UK energy and renewables organisations in 2026 are listed below. Each one holds a CREST penetration testing accreditation and shows public energy, operational technology or critical infrastructure work, and each is compared on published pricing, retests and report turnaround.

1. Arcanum Cyber

Arcanum is a UK cyber security consultancy with a dedicated energy and renewables page, a separate operational technology page that describes its CREST accredited penetration testing team, and a page for COMAH sites. Its penetration testing page says it can re-test key fixes if needed. CREST-accredited for penetration testing. Verified: CREST Marketplace listing.

2. EJN Labs

EJN Labs is a CREST-accredited UK penetration testing consultancy with a dedicated energy and renewables penetration testing service covering customer and trading portals, asset-monitoring platforms and EV charger backends, tested from the IT side of the IT/OT boundary. It is the only company on this list that publishes its 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 and Cyber Essentials Plus. Verified: CREST Marketplace listing for EJN Labs.

For an energy 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 a regulator, a licensee, a network operator or a customer security questionnaire asks for, is part of the original quote. Findings are delivered live to a client portal as they are confirmed, so your IT team or managed provider can start fixing on day one. The report arrives on the last day of testing, the only stated report 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 customer, trading or asset data. EJN does not test live control systems. Production systems on the IT side can be tested where required: checks are safe-by-default, denial of service is never run against production, and any work that reaches towards operational technology only goes ahead against an agreed safe test plan with your engineering team, defined change windows and a kill switch. Out of hours or overnight slots are available so operations and trading 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 regulator, a customer’s security team, an insurer or an auditor.

Arcanum’s separate energy, operational technology and COMAH pages keep it first on sector depth. 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. Pen Test Partners

Pen Test Partners is a UK security consultancy whose OT, ICS and IIoT security testing page lists UK distribution network operators and vertically integrated energy companies among the organisations it works with and states that it has helped operators of essential services with RIIO-2 submissions. CREST-accredited for penetration testing, vulnerability assessment, incident response, application and mobile application security testing, and threat led penetration testing. Verified: CREST Marketplace listing.

4. Bridewell

Bridewell is a UK cyber security and managed services company with a dedicated energy industry page that says its services help energy sector organisations meet their regulatory requirements and sets out the challenges of energy OT environments. CREST-accredited for penetration testing, vulnerability assessment, incident response, incident exercising, security operations centre and threat led penetration testing. Verified: CREST Marketplace listing.

5. NCC Group

NCC Group is a global cyber security company with a published energy and utilities sector page covering operational technology security. CREST-accredited for penetration testing, vulnerability assessment, incident response, incident exercising, security operations centre, threat intelligence and threat led penetration testing. Verified: CREST Marketplace listing.

6. Cyphere

Cyphere is a UK penetration testing consultancy with a dedicated energy cyber security page offering CREST accredited penetration testing for energy OT, smart meter APIs and renewable control systems. Its home page states that it includes unlimited retests for 12 months for all critical and high risk issues. CREST-accredited for penetration testing. Verified: CREST Marketplace listing.

7. CyberLab

CyberLab is a UK cyber security company whose OT penetration testing page names energy among the infrastructure operators facing regulatory pressure and maps its testing to the NIS Regulations 2018 and the NCSC Cyber Assessment Framework. Its penetration testing page lists a re-test among what is included. CREST-accredited for penetration testing and vulnerability assessment. Verified: CREST Marketplace listing.

8. Prism Infosec

Prism Infosec is a UK cyber security consultancy with a utilities sector page covering energy, water and telecommunications, which offers penetration testing of OT/ICS and SCADA systems and enterprise networks. CREST-accredited for penetration testing, vulnerability assessment, incident response, incident exercising 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 public evidence of work in the energy sector. 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.
• Energy sector evidence. A general penetration testing company was not enough. Each entry needed a public page showing energy, operational technology or critical infrastructure work: a dedicated energy or utilities sector page, or an OT and industrial control system testing page that names energy operators. 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 prices for penetration testing on a public page. General statements about what the market charges were not counted as a company’s own pricing.
• Retests and report turnaround. An energy business usually has to show that findings were fixed, and often by a regulator’s or customer’s deadline. 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 eight companies hold verified CREST penetration testing accreditation, show a United Kingdom headquarters on their listing, and have public energy or operational technology evidence. 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 energy and renewables organisations have to have a penetration test?

No rule names a penetration test as mandatory for an energy organisation. The duty that leads larger operators to commission one is broader. Regulation 10(1) of the Network and Information Systems Regulations 2018 requires an operator of essential services to take appropriate and proportionate technical and organisational measures to manage risks to its network and information systems, and regulation 10(3) requires those measures, having regard to the state of the art, to ensure a level of security appropriate to the risk. Regulation 10(4) requires the operator to have regard to guidance from its competent authority.

The Regulations only apply to operators that meet the thresholds in Schedule 2, for example electricity suppliers serving more than 250,000 final customers. For the electricity subsector, Schedule 1 names the Secretary of State and the Gas and Electricity Markets Authority, acting jointly, as competent authority, and Ofgem publishes guidance for operators of essential services. Security is usually assessed against the NCSC Cyber Assessment Framework, which is outcome-based and does not require a penetration test. Its principle B4 lists regular vulnerability and security assessments, such as penetration tests and vulnerability scans, as one way to show vulnerabilities are managed, and warns operators to consider carefully how they test live operational technology.

That warning is why scoping matters. Many buyers split the work: testing of customer portals, trading platforms and asset-monitoring backends from the IT side, and separate, carefully planned work on operational technology. The NCSC also runs a scheme for assured penetration testing of public sector and critical national infrastructure systems. If a regulator or buyer specifically asks for a provider approved under that scheme, you need a provider that holds the approval. EJN Labs is CREST-accredited, and it suits requirements that ask for a CREST-accredited penetration test. For the scoping question itself, see our guide on which energy companies are in scope of Ofgem NIS.

What an energy organisation 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. What will you test, and what will you not touch? Ask where the line sits between IT systems and live operational technology, and who signs off any work that reaches towards control systems.
3. Is a retest included, and for how long? Regulators, licensees and customers ask for evidence that findings were fixed, so a retest that is capped or charged separately changes the real price.
4. When do we get the report? If a regulatory submission, an audit or a contract award is driving the test, the gap between the end of testing and the report matters.
5. Can you test without disrupting trading or operations? Ask about out of hours testing, change windows, and how disruptive checks are handled on live systems.
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 energy and renewables.

Related: Penetration Testing Cost for UK Energy and Renewables Businesses.