Cool cities: the urban heat paradox

The world is getting hotter, and the pace of that change is faster than at any point in recorded history. In the UK, heatwaves are becoming more and more normal and, according to NASA climate scientists, the speed of warming since the mid-20th century is unprecedented.

If we’re going to create thriving, net-zero cities for tomorrow, we’ve got to start cooling down to power up.

When sunny turns scary

Summer in the UK used to mean washed out BBQs, flip-flops and maybe – if you were lucky – a single scorched day at the beach. But it’s becoming an increasingly serious health risk. In 2022 alone, more than 60,000 people across Europe died from extreme heat. And with temperatures rising so rapidly, this isn’t a future problem – it’s already knocking at our door.

Take June 2025: a high-pressure system over southern England quietly spread across the nation, bringing blue skies, rising temperatures… and a hidden danger to homes, health and infrastructure. Cities – already prone to becoming heat islands due to dense buildings, dark surfaces and heavy traffic – are especially at risk.

So, what’s the paradox?

As cities heat up, our demand for cooling skyrockets. But traditional cooling systems like air-con units literally guzzle energy and are responsible for significant emissions, contributing to the very climate crisis that caused the heat in the first place.

It’s a vicious cycle – and one we urgently need to break.

To do that, we need cooling solutions that aren’t just efficient – they’re green, smart and future-ready.

And that’s exactly what we’re working on at E.ON – transforming heat-trapped hotboxes into resilient, refreshing cities that can handle the heat and still achieve clean energy.

Here are just a few ways we’re helping cool the cities of tomorrow:

Silvertown: designing a cool district from day one

One largely untapped sustainable resource for cooling cities is district cooling – where chilled water, transported through insulated pipes from a central source, provides efficient cooling to multiple buildings at once.

It’s a smart, low-carbon approach, and it’s exactly what we’re rolling out in East London with the UK’s very first E.ON ectogrid™ installation at the Silvertown development.

Just a stone’s throw from London City Airport — where summer temperatures soar and concrete radiates heat – we’re helping transform the historic Royal Docks into a blueprint for modern urban cooling.

At of the heart of the development is ectogrid™ – our revolutionary low-carbon energy network that will serve more than 6,000 homes and businesses. By balancing energy needs across heating and cooling, the system can cut emissions by up to 88% compared to traditional gas boilers.

District cooling systems like this can draw from a variety of sources – from rivers and lakes to industrial waste heat or cold, brought to the right temperature using chillers or heat pumps. They’re especially effective in densely populated areas and can be paired with thermal storage so chilled water produced overnight, when energy demand is low, can be stored and used during the day.

And unlike standard air conditioning units, district cooling doesn’t eject waste heat into already overheated cities.

Citigen: hidden hero of the Square Mile

Tucked behind a historic Port of London façade, Citigen is one of the UK’s most quietly revolutionary energy sites. Using boreholes drilled 200 metres beneath the City of London, it taps into the earth’s natural warmth to provide carbon-free heating and 2.8MW of cooling capacity (via its own district energy network) to nearby homes and offices – 13,600 to be exact.

It also captures and recycles the waste heat from power generation, avoiding the need to vent it into an already overheated city.

Citigen is also home to our UK Energy Control Room, where energy at more than 70 sites across the country is monitored and managed in real-time – keeping cool heads (and buildings) as the mercury rises.

Solar that heats AND cools?

We’re also exploring next-gen technologies that blur the line between heating and cooling.

At the British Library, our partners at Naked Energy have delivered the UK’s largest solar heat installation to date – using their VirtuHOT collectors. Unlike traditional solar panels, these generate both electricity and high-grade heat, helping to power the building and pre-heat hot water.

This innovative system will supply sanitary hot water and space heating, benefiting both staff and visitors. And by reducing emissions and improving comfort in the Grade I listed building, it also helps to maintain the precise temperature and humidity conditions needed to preserve the national collection cared for by the British Library. 

Keeping patients at the perfect temperature at QMC

It’s not just historic libraries and landmark districts that benefit from smarter cooling. Hospitals, where temperature control is vital for patient care and medical equipment, are also feeling the heat.

At Queen’s Medical Centre (QMC) in Nottingham, we’re installing a 4MW heat pump system with 2.88MW of cooling capacity, delivering renewable heating and cooling by drawing warmth from the air – and the earth beneath it. To do that, we’ve drilled 64 boreholes, descending up to 250 metres underground, to tap into the earth’s stable temperatures year-round.

This is all part of a £15 million new energy centre (which is also operated by E.ON Control Solutions!), that will keep QMC running efficiently and comfortably for years to come. It’s a vital step in helping the NHS to reduce carbon emissions while maintaining the precision and reliability a major hospital demands.

From protecting public health to keeping businesses running during climate shocks, resilient cooling is what will separate successful future cities from sweltering ones.

It’s why we’re embedding cooling innovation in every corner of the urban map — from deep beneath London to the rooftops of libraries, and the blueprints of new city districts.