Microsoft waited seven years for a grid connection

Microsoft applied to connect its Park Royal data centre to the British transmission network on 21 January 2020. The date National Grid is now held to is 30 August 2027. Seven years and seven months.

The building went up in the middle of that wait. What took the time was the power.

Distribution route, 66kVTransmission route, 400kV

1. before 2020Microsoft approaches the local distribution networks. Their capacity and energisation programme make the delay unacceptable.
2. 21 Jan 2020The application reaches National Grid through the system operator. 120MVA.Four years from the application to the funding application
3. 15 May 2020National Grid makes the offer, with completion set at 28 November 2024.
4. Dec 2020Microsoft takes planning permission with its developer Goodman.
5. 25 Jan 2021Microsoft signs and the system operator countersigns.
6. Nov 2022 to June 2024The data centre envelope package, for Mace.
7. during FEEDThe design fails.Not enough space at Kensal Green 400kV for two connections. One moves to Willesden 400kV.
8. 31 Jan 2024National Grid applies to Ofgem for funding outside its price control. The new date, 30 August 2027, is already in the same document.
9. May 2024 to May 2025Towpath phase one. The 1960s oil-filled 275kV circuit comes out.
10. 9 Aug 2024The system operator applies to register the two UK Power Distribution circuits at Willesden 66kV as Powergate GSP.
11. 9 Dec 2024Ofgem allows £1.66m of the £1.75m requested, in 2018/19 prices, direct costs only.
12. May 2025The Willesden 66kV circuit is energised, feeding the London Powergate 2 Circuit.
13. July 2025Towpath phase two begins.
14. Oct 2025Phase two goes on hold. Towpath closures are barred October to March.Eleven months stopped, October 2025 to September 2026
15. Dec 2025National Grid confirms a new power feed from Willesden, commissioned for distribution supplies. The project is called ongoing.
16. 14 Sept 2026, plannedPhase two due to resume, with a towpath closure to 5 October. National Grid's page, read on 21 September 2026, still puts this in the future tense.
17. 30 Aug 2027Delivery date in National Grid's licence.

Application 21 January 2020 to licence delivery date 30 August 2027: seven years and seven months.

Source: UK electricity grid map, 23 September 2026

What Microsoft built

520,750 sq ft over five storeys, 96MW of data capacity, and the envelope subcontractor calls it the largest data centre Microsoft has built in the UK. It sits in north Acton, west London.

Microsoft took planning permission in December 2020 with its developer Goodman, and built it with Mace. Its own published programme was six months of site setup and 24 months of construction from the first half of 2023. Those two durations are the only numbers Microsoft publishes about the project: its page gives no capacity, no floor area, no cost and no opening date. Every other figure in this piece comes from the regulator, the network owner or the contractors. The facade package ran November 2022 to June 2024. In January 2024 National Grid told Ofgem that Microsoft had reported no delays and that its planned opening in the first half of 2025 could be assumed.

It needs 120MVA.

Why it went to the transmission network

Microsoft tried the local distribution networks first. National Grid records the outcome: "due to their limited capacity and energisation programme, the delay was not acceptable which led to an application to NGESO for a connection to the transmission network".

That is the hyperscaler's problem in one sentence. The distribution network could connect it, but not soon enough, so Microsoft went up a voltage level to the grid itself.

The clock

• 21 January 2020: the system operator puts Microsoft's application to National Grid. Microsoft's own application came first, so the real wait starts earlier than any date on the record.
• 15 May 2020: National Grid makes an offer, 115 days later, with completion set at 28 November 2024.
• 25 January 2021: Microsoft signs, and the system operator countersigns.

Microsoft never contracts with the company building its connection. It signs the industry code with the system operator, which contracts with National Grid separately. If it walks away before the works finish, it pays the costs incurred to date.

What Microsoft was owed, and what it bought

National Grid's obligation was three connections at Willesden 66kV. Two of those already sat under a distribution operator's agreement, so National Grid's own new obligation was exactly one more 66kV connection.

Microsoft asked for more. It wanted two geographically separate supply points, so that "no single event would disconnect Microsoft sensitive customer data". Everything above the minimum it pays for itself, through a One-off charge whose amount is redacted.

What that bought was four connections in two contracts:

• two at 66kV, built by UK Power Distribution Ltd, company number 06339585, an independent distribution network operator licensed by Ofgem
• two at 400kV, built by National Grid: one from an extended Willesden 400kV substation, one from an extended Kensal Green 400kV substation

That second pair is the point of the whole exercise. Not one connection carrying the load, but two paths from two separate sites, so that losing a substation does not lose the data centre. And the submission's diagrams label each connection 120MVA, the same figure it gives for the data centre as a whole. These are not two halves of the load. Each path is sized to carry it.

Connection	Built by	Contract held by	Status
66kV, Willesden to Powergate	UK Power Distribution	UK Power Distribution	Energised 2025
66kV, Willesden to Powergate	UK Power Distribution	UK Power Distribution	Energised 2025
400kV, Willesden to Powergate	National Grid	Microsoft	Due 30 Aug 2027
400kV, Kensal Green to Powergate	National Grid	Microsoft	Due 30 Aug 2027

Source: UK electricity grid map, 23 September 2026

All four land at Powergate, Microsoft's own 66kV substation, a three-storey building with a basement and rooftop plant that Microsoft builds and owns. The two 66kV circuits take bay positions inside National Grid's Willesden substation, and National Grid competitively awarded a main works contract to design and build those two bays; the contractor and the form of contract are redacted.

Side	Party	What they build
Distribution	UK Power Distribution Ltd, 06339585	Two 120MVA connections at Willesden 66kV
Grid	National Grid Electricity Transmission, 02366977	Two 120MVA connections from Willesden 400kV and Kensal Green 400kV
Grid	J. Murphy & Sons Limited	Cable works along the Grand Union Canal towpath
Grid	Not published	Main works contract for the two connection bays at Willesden 66kV
Microsoft	H&MV Engineering	Electrical substation at Powergate, including energising the 66/20kV transformers
Microsoft	J Coffey Construction Ltd	Powergate substation civils, enabling works to internal finishes
Microsoft	Mace	The data centre building
Microsoft	Goodman	Developer of the data centre, with Microsoft

Source: UK electricity grid map, 23 September 2026

Microsoft is also paying for a connection it will not use. Setting out why its option was the right one, National Grid records that "Space provision for a future connection has been maintained", that it is "customer agnostic and can provide quicker connections in the future", and that its provision "has been agreed to be funded by the customer and thus is not burdened by the consumers". The hyperscaler buys the headroom for whoever connects next.

Then the design failed

The original offer put both National Grid connections at Kensal Green 400kV. During Front-End Engineering Design that became unbuildable: there was not enough space to install new assets on the site, and only one connection could come from there.

One connection moved to Willesden 400kV. Microsoft still has two supply points, but three of its four circuits now originate at Willesden.

The date moved 33 months

The completion date went from 28 November 2024 to 30 August 2027, a move of 33 months. Both dates are printed in the same January 2024 submission, so the whole movement was on the record by then.

The instrument was an Agreement to Vary, signed by Microsoft, which re-scoped the connection and set the new date. And the date is Microsoft's own: National Grid tells Ofgem the works "facilitate the customer's desired connection date of 30th August 2027 which aligns with the customer's data centre construction programme".

So the grid is held to a date the customer asked for, two years after the opening Microsoft had given the same regulator in the same document.

Who pays

Consumers pay £1.66m, against £1.75m requested, in 2018/19 prices. That covers direct costs only; indirect costs run through a separate mechanism. It is not the cost of the project, and no document publishes that total.

It is also priced on something nobody is building. National Grid states the costs it put to Ofgem "are for a third, theoretical connection to Willesden 66kV and this is the basis of the cost build up and the funding application": the minimum it was obliged to provide, not the four circuits it is actually delivering. Microsoft funds the difference.

Not to scale. Only the first part has a published figure, so the blocks carry no proportion.

• Direct costs, final determination allowanceElectricity consumers, against 1.75 requested1.66£m, 2018/19 prices
• Indirect costsElectricity consumersrecovered separately
• Everything above the minimum, including the two 400kV connectionsMicrosoftredacted
• Space held for a future connection at WillesdenMicrosoftnot published
• Total project costSplit of the aboveredacted, published by nobody

Source: UK electricity grid map, 23 September 2026

The application to Ofgem only happened because the timing fell wrong: Microsoft's request arrived the month after National Grid filed its RIIO-T2 business plan, so the works sat outside the price control and needed a separate re-opener, which came four years later in January 2024.

What is actually energised

The distribution half is live

In August 2024 the system operator applied to register the two UK Power Distribution circuits at Willesden 66kV as a new Grid Supply Point, Powergate GSP. In May 2025 a contractor on the works reported that National Grid "successfully energised the new circuit feeding the 66kV substation at Willesden, which in turn feeds the London Powergate 2 Circuit at 66kV", with H&MV Engineering energising the transformers behind it and load-testing "before final clearance from National Grid for commercial operation". In December 2025 National Grid confirmed "the commissioning of a new power feed from Willesden substation" for distribution supplies to a Park Royal data centre, and called the project ongoing.

The transmission half is not

The 400kV route runs along the Grand Union Canal towpath. Phase one removed the old cable, 8,400 metres of oil-filled 275kV circuit laid in the 1960s, between May 2024 and May 2025. Phase two began in July 2025, stopped in October 2025 for winter moorings, and was due to resume on 14 September 2026. Towpath closures are barred from October to March, which shuts the route for half of every year.

National Grid's 2025/26 annual report lists among its achievements that it "Energised the first Microsoft data centre connection". It names no site.

What this tells you

Microsoft's building was finished roughly on its own schedule. Its permanent transmission connection was not, and will not be until August 2027 at the earliest: seven years and seven months after it applied, of which 33 months is slip on top of an original offer that was already four years and ten months long.

The distribution route carried the load in the meantime. A hyperscaler that went to the transmission network because distribution was too slow ended up energised, first and so far only, through a distribution operator.

There are three things a hyperscaler should read off this.

The connection is not one thing

Four circuits, two contracts, two builders, a third contract for the bays, and a substation you build and own yourself.

The date is yours, not the grid's

The 2027 deadline is the date Microsoft asked for, and the regulator holds National Grid to the date, not to the money.

You pay for the next customer

The headroom held open at Willesden is funded by Microsoft and explicitly not by consumers.

National Grid expects a new substation at Uxbridge Moor to connect more than a dozen data centres from 2029. Each of them starts the same clock.