The one-time owner of a London coffee shop now has a paper fortune worth an estimated $155m (£115m) after a deal with a Japanese utility firm valued Octopus Energy, the sustainable energy business he founded little more than five years ago, at $2 billion. Greg Jackson, a serial entrepreneur, owns a 7.4% stake in Octopus, the UK’s fastest growing energy supplier. Octopus only attained ‘unicorn status’ – a term used to describe young start-up companies worth $1bn – earlier this year. A new investment agreed on Wednesday has doubled that value in the last eight months as it begins its global expansion. Octopus Energy will now supply electricity to homes in Japan under deal struck with Tokyo Gas, the largest gas utility company in Japan. Under the terms of the deal, Tokyo Gas will help establish the Octopus Energy brand in Japan as part of a new 30:70 joint venture, and will also buy a 9.7% stake in Octopus Energy for $200m, which values the company at $2.1bn. Jackson, who is also the chief executive of Octopus Energy, said the investment would “turbocharge our mission to revolutionise energy globally”. The rapid growth of Octopus means it is fast catching up with Centrica – the owner of the UK’s biggest energy supplier, British Gas. Centrica is valued at £2.5bn and also includes a string of power plants, North Sea oil and gas fields, and a stake in the UK’s nuclear reactors. British Gas has some 12 million customers, while Octopus supplies 1.8m homes in the UK and is growing quickly across global energy markets. In addition to boosting Jackson’s personal fortune, the deal will also provide a Christmas windfall for Octopus Energy’s staff. The company’s permanent employees – which number around 1,000 across its global offices – own 5% of the business , a stake which is now worth $100m, equal to an average $100,000 for every staff member. Jackson, who was also a founding investor in property management platform Rentify, founded Octopus Energy in 2015 with the backing of Octopus Investments, the UK’s biggest investor in solar power. On its website the company says it set out to disrupt the energy industry because it is “ruled by a handful of complacent dinosaurs peddling fossil fuels, pricing trickery and poor customer service”. It says it offers homes 100% renewable electricity which is “good for the planet, good for your wallet”. Octopus Energy only became a $1bn UK “tech unicorn” eight months ago after the sale of a 20% stake to Australian utility company Origin Energy for $200m. The Sydney-headquartered company invested a further $50m in Octopus alongside the Tokyo Gas deal to maintain its stake in the company. Jackson said: “When Origin invested less than eight months ago, we said it was fuel for stage 2 of our mission. Since then, Octopus Energy has accelerated that mission to make the global green revolution faster and cheaper by launching Octopus Energy Germany and New Zealand, acquiring Octopus Energy USA and acquiring Upside Energy to deepen our smart grid capabilities with their powerful technology.” Octopus Energy’s growth has been driven in large part by its software, Kraken. The technology platform makes it easier for energy suppliers to offer their customers “smart” renewable energy tariffs that integrate home batteries and electric vehicles to make using renewable power cheaper. Earlier this year Octopus was able to pay customers on its Agile tariff to use more electricity at home as renewable energy generation soared, by reflecting the “real-time” market price of green electricity. Octopus has licensed the Kraken tech platform to UK suppliers including E.ON UK and Good Energy. Globally, there are more than 17m homes connected to the Kraken platform, and Octopus hopes to reach 100m within the next few years. Gerry Grimstone, the minister for investment, said: “Japan is one of our largest trading partners and it’s fantastic to see how, following our historic trade deal, UK companies like Octopus Energy Group are securing Japanese investment in our world-leading renewable energy industry.”