London's climate tech scene is easiest to find in three places: the Sustainable Ventures hub in County Hall on the South Bank, the companies headquartered across the capital such as Octopus Energy, Kraken, Greyparrot and Sylvera, and a calendar that peaks every June with London Climate Action Week. Outside that week, the most dependable gatherings are the hub events at County Hall, the pitch days run by the Climate Tech SuperCluster, the Innovation Zero congress at Olympia each spring and the London chapter of Climate Tech Cities. All of the organisations below had live, current pages when we checked them in October 2026.

The sector at a glance

Climate tech covers any business whose product cuts emissions, removes carbon or helps people adapt to a warmer climate. In London the work splits roughly into software for energy companies, data and ratings for carbon markets, waste and materials, and hardware spun out of university labs. No single district holds it all. Some companies sit in West End offices, others in converted warehouses in south-east London, and a large share of the early-stage firms rent desks in one building on the Thames.

A few reference points, all checked October 2026:

  • Biggest annual gathering: London Climate Action Week, held 20 to 28 June in 2026.
  • Largest dedicated workspace: Sustainable Ventures at County Hall, Belvedere Road, SE1.
  • Best known homegrown company: Octopus Energy, whose software arm Kraken is being spun out as a separate business.
  • Main spring trade event: Innovation Zero at Olympia, booked for 27 and 28 April 2027.

County Hall and Sustainable Ventures

If you visit one building, make it County Hall. Sustainable Ventures occupies a refurbished floor of the former seat of London government, next to the London Eye, and runs it as workspace for climate startups. The organisation says its wider ecosystem now counts more than 1,000 startups, with hubs in London, Manchester, Glasgow and Cambridge (checked October 2026). Its homepage quotes Howard Dawber, Deputy Mayor of London for Business and Growth: "Sustainable Ventures is the epicentre of the green and climate economy."

According to a Big Issue profile of the hub, Sustainable Ventures was founded in 2011 by Andrew Wordsworth, and the County Hall space houses around 160 climate-focused companies in 40,000 square feet. Wordsworth put the appeal of clustering plainly: "We can bring investment opportunities by literally walking around the building."

The building is also an events venue. During London Climate Action Week the hub runs its own programme, and the Sustainable Ventures LCAW page records that its 2025 edition drew more than 2,600 visitors to 26 events with 89 speakers. For 2026 it planned a week of panels and showcases from 22 to 26 June, including a Climate Tech Mixer on the Thursday evening. Outside June, watch the same site for hub events and for programmes aimed at early-stage founders.

Companies worth knowing

The firms below were chosen because each is still operating, still has a London base on its own official site, and illustrates a different corner of the sector. This is a sample, not a ranking.

Octopus Energy and Kraken

Octopus Energy is a supplier with a registered address on Oxford Street in the West End. Its bigger story for the tech community is Kraken, the software platform it built to run customer accounts and energy assets. On 29 December 2025 the group announced it would spin out Kraken at a valuation of $8.65 billion after a $1 billion investment round, with Octopus keeping a 13.7% stake. The release names London and New York as Kraken's headquarters and says the platform is contracted to serve more than 70 million accounts. Octopus founder Greg Jackson said: "As an independent company with world-class backers and outstanding leadership, it will be free to grow even faster." The Kraken site itself lists utilities including EDF, E.ON, Origin and Tokyo Gas among its clients.

Greyparrot

Greyparrot builds AI that watches conveyor belts in recycling plants and identifies what passes underneath. Its site gives a registered address on Drummond Road, SE16, and reports more than 300 Analyzer units deployed in over 65 materials recovery facilities across more than 20 countries, with 52 billion waste objects analysed in 2025 (checked October 2026). Customers it names include Biffa and Veolia, and brands such as Unilever use its packaging data.

Sylvera

Carbon credits are only worth buying if the underlying project does what it claims. Sylvera sells ratings and market data on that question to buyers, governments and project developers. Its careers page lists London as one of five hubs, alongside New York, São Paulo, Singapore and Tokyo, and puts the team at about 130 people (checked October 2026).

Startups from university labs

Imperial College London is a steady source of new companies. Its Enterprise Lab runs the Venture Catalyst Challenge, a three-month programme for Imperial students, recent alumni and early-career researchers with an Energy and Environment track; the 2026 grand final is on 4 November (checked October 2026). For more advanced firms, Imperial leads EarthScale with Undaunted: a 12-month, UK-wide programme for climate tech ventures that have seed funding and early commercial traction, offering up to £14,000 in vouchers and taking no equity. Its second cohort runs from June 2026 to June 2027, and applications for a third cohort were due to open in late 2026.

London Climate Action Week

Most of the year's climate networking in London happens in one week. The think tank E3G co-founded London Climate Action Week with the Mayor of London in 2019, still hosts it and keeps a year-round secretariat. The format is open: organisations of every size put on their own events and list them on the official calendar, so a founder breakfast and a bank's investor summit can sit on the same morning.

The 2026 edition ran from 20 to 28 June and was its eighth, as the Grantham Research Institute at LSE noted. Organisers usually describe it as more than 1,000 events and 75,000 participants over nine days, and the Science Based Targets initiative reported afterwards that 2026 was its biggest yet, with more than 1,300 events and over 100,000 attendees.

Three fixtures tend to matter most to people in climate tech:

  • Climate Innovation Forum. Run by Climate Action, the Climate Innovation Forum opened the 2026 week at Guildhall on 22 June, its eighth year, with 2,500 leaders expected.
  • Cleantech Venture Day London. Founders pitch to investors at KPMG in Canary Wharf (details below).
  • County Hall programme. The Sustainable Ventures week, mixing panels with evening socials.

Expect the 2027 week in late June. Plan early: popular sessions sell out, and many smaller events open registration only a few weeks ahead.

Pitch days and conferences

Cleantech Venture Day

The Climate Tech SuperCluster runs Cleantech Venture Day as a series across European cities. The London edition was held at KPMG, 15 Canada Square, on 25 June 2025 and again on 22 June 2026. The 2026 event page lists Cambridge Cleantech and the SuperCluster as organisers in partnership with KPMG, with 16 startups pitching across pre-seed, seed and Series A and B stages. Speakers included Nigel Topping, Chair of the Climate Change Committee. It sold out.

When the 2025 edition was announced, Cambridge Cleantech chief executive Sam Goodall, a co-founder of the SuperCluster, said: "It has never been more important for good climate crisis solutions to be heard." If you are a founder, the pitch slots are competitive; if you are an investor or job seeker, the audience is the point.

Innovation Zero

Innovation Zero is a two-day congress and exhibition on deploying low-carbon technology, aimed at buyers, investors, engineers, policymakers and suppliers. The next edition is booked for Tuesday 27 and Wednesday 28 April 2027 at Olympia, W14 (checked October 2026). It suits people who want to meet companies already selling at scale rather than seed-stage founders.

Communities that meet between the big events

The June peak can make the rest of the year look quiet. It is not, but the regular events are spread across many hosts, so it helps to follow a few aggregators.

Climate Tech Cities calls itself the largest place-based climate tech community in the world, with more than 25,000 members, and has a London chapter alongside chapters in cities such as New York and Amsterdam. Its London arm publishes the London Climate Tech newsletter, whose guide to the 2026 Climate Action Week was co-written by co-founders Alec Turnbull and Sonam Velani with contributors from Streetlife Ventures. Streetlife hosts a Cities x Climate Breakfast for founders and funders.

We looked for the three standing groups that often appear in generic guides, a "London Climate Tech Meetup", a "Sustainable Finance Forum" and a "CleanTech Meetup". We could not find a current official page for any of them, so we have left them out. Several once-regular gatherings have also gone quiet: one popular monthly climate social we found had not posted a new date since 2024. Before you travel, check that the listing shows a date in the coming weeks.

How to choose events and get value from them

Match the event to what you need. Hiring and job hunting work best at evening socials and community meetups, where people talk freely. Fundraising conversations happen at pitch days and investor breakfasts, which often need an application. Corporate procurement and partnerships belong at trade events like Innovation Zero.

A few habits help:

  • Check the host. Look for a named organiser, a venue address and a date. Anonymous listings without either are best skipped.
  • Read the price carefully. Community events are often free; conferences charge, and some pitch days only admit selected founders and invited investors.
  • Prepare a two-line introduction. Say what you do and what you are looking for, whether a job, a pilot customer or a co-founder.
  • Follow up within a few days. Hub communities are small enough that people remember who sent the useful note.

If you are moving to London for climate work, rules on the right to live and work in the UK are set out on GOV.UK's visas and immigration pages. For other city guides, the London Society homepage collects our coverage of the capital, and our sister guide, the Cambridge Society, covers Cambridge.

Frequently asked questions

Which climate tech companies are based in London?

Examples with a London base on their own sites include Octopus Energy and its software spin-out Kraken, waste analytics firm Greyparrot and carbon ratings company Sylvera. Around 160 earlier-stage companies work from the Sustainable Ventures hub at County Hall, according to the Big Issue.

When is the best time to meet people in London climate tech?

Late June, during London Climate Action Week, when more than 1,000 events run across the city. Outside that week, follow the Sustainable Ventures events page and the London Climate Tech newsletter, and note Innovation Zero at Olympia on 27 and 28 April 2027.

Are London climate tech events free?

Many community and hub events are free to attend, but conferences charge and pitch days often admit founders by application only. Check each listing, since prices and formats change from year to year.