As the frost chills the ground, Britain’s data centre operators are preparing for a long, testing winter to keep millions connected through the dark and cold.
In warehouses up and down the country, racks upon racks of computer servers hum and whir in unison, processing billions of pieces of data to keep everything from emergency services to WhatsApp messages online.
There are some 450 data centres across Britain, with many concentrated within the M25, hosting the backbone of online services for the Ministry of Defence, NHS 111 and keeping companies connected to Microsoft Teams or Gmail.
The information they store and produce for users can be critical. Overheating at data centres in London over the summer caused an IT meltdown at Guy's and St Thomas's hospital and made digital patient records inaccessible.
Big Tech giants such as Amazon and Microsoft have invested billions of pounds in UK data centres, while others are operated by specialist companies such as Equinix. These server farms now consume as much as 2.5pc of the UK’s electricity.
This winter, unlike no other, they are having to prepare for the unthinkable. As Vladimir Putin's war on Ukraine continues, National Grid has warned of the possibility of planned blackouts if the weather turns particularly cold and gas supplies from Europe are cut.
“What National Grid are most worried about is Christmas to the middle of January,” says one source close to the data centre industry. “There is peak danger when the margins narrow.
“What might happen this time is it is not an unplanned event like a storm, it is potentially prolonged and regular disruptions to power supply.”
While energy bosses have insisted such a scenario is unlikely, data centre operators have made their own preparations.
Rusty King, European chief technology officer at data centre manager Thrive, says: “We have the ability with our site to run for probably three to four days on diesel generators, although we don’t expect an issue of that long, and we have contracts with agreements to refill in 12 hours.”
Most data centres are equipped to operate in the event of a planned or sudden power outage, coming with large back-up diesel generators that can be powered up in 15 minutes.
While many data companies have touted investments in clean energy and renewables, nearly all are set up to switch on fossil fuel powered generators in a crisis.
Normally, they would keep up to three days of fuel handy, but since the summer most have been stockpiling diesel so they can run for up to three weeks, according to some in the industry.
Equinix, one of the world’s largest data centre operators, has already boosted its supplies ahead of the winter, according to Gary Aitkenhead, a senior vice president at the US-listed company.
The company has been “taking additional measures to ensure a good diesel stockholding,” he says. “It is highly unlikely there will be a need to run for more than a few hours, or at worst case a day, on diesel, but Equinix is prepared to run for up to a week following further contingency planning.”
Others have been trying to ensure they get priority for extra deliveries of diesel over the winter period in the event that blackouts do become a reality.
The winter worries come after data centres were forced into drastic action by a scorching summer, when the mercury hit over 40 degrees celsius in parts of Britain. Some turned to interventions such as running hoses on to the roof to keep their systems cool.
Google suffered outages, blaming the hot weather for a decision to shut down some machines to prevent damage, as did rival Oracle.
Ahead of winter, tech companies held meetings with regulators, environmental authorities and the Government to try and ensure they were near the top of the list when it came to blackout warnings and fuel supplies.
Some have also been lobbying to have more data centres classified as Critical National Infrastructure, to put them front of the queue for supplies of fuel in a crisis.
National Grid tries to keep the “core frequency” of the energy network to around 50Hz, but spikes in demand can cause that to wobble and lead to power outages.
In 2019, such a drop in frequency was caused by a lightning strike that took out an electricity pylon in north London, triggering a blackout for millions. The grid operator is now offering to pay some companies and industries to cut the amount of power they are using during peak periods of demand.
One data centre industry source said the long-term hope was that some centres would be placed on a “protected site” list. This list includes facilities such as hospitals, oil refineries, airports, major rail infrastructure, water, food production and the armed forces.
However, such sites normally have a separate energy system in place via a “discrete feeder”, meaning they can be isolated from a wider planned blackout. This is not the case with most data centres, as they are connected to the main power grid and also have back-up generators.
As well as being frustrating for customers, for data centre providers, going offline is costly. According to the Uptime Institute, 25pc of outages cost service providers more than $1m.
John Booth, of the National Data Centre Academy, says: “We understand that the DCMS are engaged in talks with the main operators to secure additional diesel supplies should there be prolonged power outages if they are considered to be Critical National Infrastructure.
“We also understand that power outages will be communicated to operators one day before the event so IT loads can be transferred to locations that will not experience an outage.”
There have also been calls to loosen rules at the Environment Agency over the use of polluting diesel generators. The tight rules around these mean they need to be powered up at the last minute. It is understood there are no changes planned by regulators.
The most recent cold snap has brought concerns around blackouts into sharp focus. Data centre operators will be hoping they have done enough to weather the bleak months ahead.