The grid is full: what happens when a city's energy transition runs out of wire?

In 2015, Ireland’s data centres used 5% of all the electricity metered in the country. Ten years later they used 23%, according to the Central Statistics Office. That is not far behind every home in Ireland put together, urban and rural, at 28%.

From our library

Data Centres Metered Electricity Consumption 2025 — Key Findings (CSO, 7 Jul 2026)

Data centres consumed 7,663 GWh in 2025—23% of national metered electricity, up tenfold since 2015.

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The growth has not slowed. Between 2024 and 2025 data centres’ consumption rose by 10%, from 6,973 to 7,663 gigawatt hours. All other customers together, households and businesses, used 2% more. Total metered use in Ireland grew by 34% over the decade, and data centres account for much of that rise.

Homes and data centres also draw power differently. Household use spikes every winter, for heat and light. Data centres’ use climbs quarter after quarter, from 291 GWh in the first quarter of 2015 to 1,991 GWh in the last quarter of 2025. Watch the slope of their share in the chart below: it never turns down.

These are national numbers, and the CSO does not say where the servers sit. Dublin’s energy agency, Codema, does give a regional picture. In its Dublin Region Energy Master Plan, data centres account for 16% of the region’s energy-related emissions, close behind commercial buildings and ahead of the whole public sector.

From our library

Dublin Region Energy Master Plan (brochure), Codema

Baseline emits 5,969 ktCO₂, heat 46%; data centres cause 16%, aiming 87% district heating by 2050.

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Codema’s requests of big consumers are practical. It asks them to minimise their impact on the grid, to generate on site and buy renewable power matched, preferably hour by hour, to their demand, and to make their waste heat available to district heating. Ireland already has a working example: since 2023, a scheme in Tallaght has piped heat from an Amazon data centre to the offices of South Dublin County Council and TU Dublin’s Tallaght campus.

Most cities will never host Ireland’s share of data centres. But any city can ask the same things before the next campus arrives. How much power will it draw at the peak, and who pays for the wire to bring it? Where will its heat go? And is there a network nearby that could take it?

Under the river Dodder, between Sir John Rogerson’s Quay and York Road in Ringsend, Dublin City Council wants to dig a tunnel for hot water. In September 2026 it published the planning notice for the Dublin District Heating Project, which would take heat from burning household waste at the Poolbeg incinerator and pipe it to 50,000 homes and buildings in the Docklands. A further 8.5km of pipe would be laid in residential streets on the north and south quays.

From our library

Heat from Poolbeg incinerator to be piped under Dodder to homes in Dublin's Docklands (Irish Times, 11 Sep 2026)

Decade‑long delays end as waste‑heat finally reaches Docklands homes via novel underground pipeline.

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The case for it is simple, as the Irish Times explains: with a heat network, switching one source to renewable or waste heat decarbonises thousands of homes at once, instead of changing boilers house by house.

The idea is older than the plant. Read the timeline for the gap between the pipe and the heat.

Codema’s master plan says district heating could supply 87% of Dublin’s heat demand by 2050, and that 3,579 MW of renewable and waste heat in the region is going unused today. Building the networks across Dublin would cost an estimated €7.7 billion by 2050, with most of it paid to local workers. The plan also notes that district heating is currently unregulated in Ireland, so customers will need protection on price and service.

That is where ownership comes in. Amsterdam’s coalition calls heat a basic service and wants a strong public heat company, built with Firan, EBN, neighbouring Diemen and other municipalities, with affordability and democratic control at its centre. Until enough sustainable sources exist, it will use leftover heat from the waste-to-energy plant and from data centres. It also admits it depends on national choices, including the government taking over private heat companies.

Denmark, where district heating is ordinary, shows what happens when take-up falters. In 2024, 30 of 75 municipalities reported a lack of progress on district heating projects, according to a status report by the think tank Concito. Fewer connections make each project costlier, which slows the network further. A pipe is only as good as the homes that agree to use it, and whoever owns the pipes decides on what terms they are asked.

In 2008, Zurich’s voters were asked to commit their city to living on 2,000 watts of energy per person and to stop renewing its investments in nuclear power. 76% said yes. At the time the average Swiss resident used about 6,000 watts, so the target meant cutting primary energy use by roughly two thirds. In 2022 voters approved a net-zero target for 2040.

A promise like that is easier to keep when the city owns the company that sells the power. Zurich does: ewz, the city’s own electricity works, runs the city’s grid, and its smart-grid work sits in our library, though the page is still thin. The 2000-Watt Society idea, born at ETH Zurich in 1998, became building rules and planning policy; the first 2000-Watt Site certificate went to Greencity, a new district at Manegg. The city’s Strategies 2040 put climate-neutral energy under “stable livelihoods”, for a population projected to pass 500,000 by 2040.

From our library

2000-Watt Society

Swiss initiative targets 2,000 W per person, limiting CO₂ to one tonne, influencing Zurich’s 2050 sustainability goals.

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Vienna is the fuller case, because its framework strategy spells out what it means to use the assets the city owns, from municipal housing to public utilities and transport, “in the common interest”. Since 2009 all of Vienna’s residual waste has gone to the city’s waste-to-energy plants rather than to landfill. The chart shows what those plants, a large heat pump and the solar arrays of Wien Energie, the city’s utility, already supply.

Owning the system lets Vienna plan the dull parts together: expanding the electricity grid for heat pumps and electric cars, extending district heating where heat demand is dense, and coordinating the digging for cables and mains with the redesign of the street above, trees included. It has set dates to end oil heating by 2035 and gas heating by 2040.

Berlin’s grid company, Stromnetz Berlin, and the city’s district heating network are in our library too, but as project pages with little yet to read, so this read draws no lesson from them. Evgeny Morozov and Francesca Bria noted in 2018 that campaigns to take grids, gas pipes and water back into public hands have often worked, and warned that a city can win back the pipes and lose the data that runs them. Ownership is a lever few cities still hold. The ones that do have something to teach the rest.

France made local energy planning a duty ten years ago. Every group of municipalities above 20,000 inhabitants must draw up a six-year climate, air and energy plan, known as a PCAET, and 750 groups are obliged. By March 2025, 552 had adopted one, 73% of those obliged, and another 97 had done so voluntarily. Three in four people in France now live in an area with an adopted plan.

From our library

PCAET : état des lieux 2025 — 10 ans de planification écologique locale (Intercommunalités de France, février 2026)

A landmark report reveals 73% of local bodies meet climate mandates, exposing funding cuts.

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Writing the plan proved easier than paying for it. In 2025 the state created a €200 million climate fund for these plans, shared out mainly by population and spent without project-by-project vetting. Councils liked the method and spent the money, but on actions that were already ripe, because the deadlines were short. Terres d’Argentan in Normandy used part of its share on a study into recovering waste heat.

Switzerland pays for the planning itself. In its 2024/25 cycle the federal programme EnergieSchweiz supported 119 projects in 460 communes with CHF 3.55 million. Look at which bars are longest below.

From our library

Projektförderung – Förderprogramm von EnergieSchweiz für Gemeinden, Programmzyklus 2024/25: Zahlen und Fakten (BFE, January 2026)

Swiss smart‑city initiative allocates CHF 3.55 million to 119 projects across 460 municipalities, highlighting five front‑runners.

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Energy plans were the single biggest category in both strands. National outlooks explain the urgency. The Dutch planning agency PBL found in its 2026 outlook that the expected cut in emissions by 2030 has stalled for three years running, and that the Netherlands imported 77% of the energy it used in 2025.

Put the sources side by side and a good local plan contains a short list of things:

1. A map of what should go where, street by street: which areas suit a heat network and which suit heat pumps. Codema built one for Dublin.
2. A register of every installation and its grid connection, kept up to date, so progress can be tracked.
3. Land reserved early for substations and cables in spatial plans, as the Dutch regional grid programme now asks.
4. A simple energy statement with every planning application, giving the building’s peak demand for heat and power.
5. One timetable for digging, so cables, heat pipes and new street trees go in together, as Vienna plans.
6. Money that arrives on a known date, for more than a year at a time: the main lesson French councils drew from their climate fund.

Most of what decides whether a city’s energy plan works happens below the pavement and inside a grid operator’s spreadsheet. Oostzaan’s whole queue could be connected after a recalculation, Dublin’s pipe waited years for its heat, and Vienna plans its digging so a street is opened once. Little of this is published city by city: grid data are mostly national, and the utility pages in our library are thin.

That gap is one we can close together. Cities that run their own utilities, like Zurich and Vienna, have learned things that cities without them need: how to read a congestion map, how to price heat, how to ask a data centre for its waste heat before the permit is signed. If you work on a city’s energy system, start with Smart Grids & Renewable Energy, where the projects and plans in this read are gathered, and with the city profiles of Dublin and Amsterdam.

Then tell us what your city has learned. Join the community on the participate page and say where your grid runs short, and what freed it up. The next read on this subject should be able to name more places than these.