Every photo you upload to the cloud, every email you send, every video you stream, every purchase you make from Amazon, every byte of telematics data your equipment generates — all of them pass through servers housed in data centers. It’s no wonder that more and bigger data centers are sprouting up around the country. In December 2018 Apple announced plans to invest $10 billion in U.S. data center construction over the next five years. Some of the largest centers span hundreds of thousands of square feet.

Imagine the electricity all those servers consume, not to mention the electricity for the cooling equipment that keeps them from overheating. Think in terms of some 90 billion kilowatt-hours of electricity per year.

Now imagine what happens if the power from the utility goes down. Not surprisingly, the stakes are high. Unplanned data center outages cost companies nearly $9,000 a minute in 2016. That’s why these centers are backed up by diesel generators, typically paired with a UPS system that kicks in automatically and draws power from a bank of batteries during those minutes when the generators are warming up and coming on line.

All well and good — but what if the generator fails? It does happen. “Generators are not foolproof,” said Brian Anulies, region product development manager with United Rentals’ Power and HVAC group. That’s where generator testing and maintenance with load banks comes in.

“A load bank simulates electrical loads for testing, validating and maintaining power sources,” said Anulies.

When a new data center is built, load bank testing is critical to verifying the operational capacity and performance of the electrical systems, including the generators, the UPS system and the power distribution infrastructure. The mechanical systems must be tested as well. Oftentimes, even before the servers are brought in, “Load banks are placed across the data center floor to ensure that the HVAC systems are capable of removing the heat that rows of servers can generate and keeping the design temperature in the room,” Anulies explained. Load bank testing can also help optimize the design of the center.

In an established data center, stand-by power systems should still be tested and load banked regularly. Compared to the cost of downtime, “The cost of testing and maintaining generators is much, much smaller,” said Anulies.

Experienced load bank experts such as those at United Rentals can customize the right load bank solution for the project. “The recipe changes with every test,” said Anulies. “We’ve had data center projects with as few as three 100 kW load banks and those with hundreds of 600 kW units on the floor.”

The success and efficiency of these projects depends on countless small but critical details, and failure to consider them can wreak havoc. United Rentals takes an “all things considered” approach to load bank tests. Project managers review and discuss every aspect of the project, from cable lengths to facility access points (door and elevator widths) to hot air discharge directions (vertical or horizontal) when developing a bill of material for jobs.

Then there is the risk of equipment damage during transportation. In conjunction with its load bank manufacturing partners, United Rentals developed shipping cages and containers that take the brunt of any impacts during over-the-road transportation, thus ensuring that customers receive fully functional and safe load banks.

Proper preventative maintenance and repairs of the load banks is also imperative. United Rentals performs a complete inspection of all load banks and cables every time they come back to the branch to ensure that they’re in ready-to-rent condition for the next customer.

Today, data is integral to business enterprises and to modern life as we know it. It’s even been called “the new oil.” Keeping data centers reliably powered is critical to keeping that “oil” flowing, and load bank testing is critical to ensuring that reliability.

Marianne Wait is an editor and writer who creates content for Fortune 500 brands.