Data center backup power: generators, UPS and batteries explained

Backup power has three layers: batteries or flywheels carry the load for seconds to minutes, a UPS cleans and switches power, and diesel generators take over for hours. Large generators are reported to take 40 to 80 weeks or more, and public data on UPS and battery lead times is thin.

Key numbers at a glance

Read these with their source and date. Several come from a trade article that does not name its sources, and those are labeled that way.

• Generac data center backlog: 1.6 billion dollars, of which about 1.35 billion dollars is scheduled for 2027 delivery (Generac Q2 2026 earnings call, 29 July 2026, company statement).
• Caterpillar Power Generation sales: 3.098 billion dollars in Q2 2026, up 29 percent, with growth "primarily in data center applications" (Caterpillar results, 4 August 2026).
• Generac data center lead times: 40 to 45 weeks, which the company says compares with 70 to 80 weeks at some competitors (same call, company statement, not independently checked).
• Generac expected 2026 data center revenue: nearly 450 million dollars (same call).
• Large diesel generator lead times above 2.5 MW: 18 to 24 months, attributed by Datacentres.com to OEM order books at Caterpillar, Cummins and Kohler (Datacentres.com, 3 September 2026, no underlying document cited).
• Installed cost of large diesel generators: 450 to 600 dollars per kW, up from roughly 380 to 420 dollars in 2023 (same article, unsourced).
• Backup power for 1 MW of IT load with full duplication: 2.1 to 2.8 million dollars installed (same article, unsourced).
• Lead-acid (VRLA) batteries: 120 to 150 dollars per kWh installed. Lithium iron phosphate (LFP): 300 to 400 dollars per kWh installed (same article, unsourced).
• Battery service life: 3 to 5 years for VRLA and 10 to 15 years for lithium-ion in data center duty (same article, unsourced).
• Vertiv inventories: 2,522.7 million dollars at 30 June 2026, up from 1,456.5 million at 31 December 2025 (Vertiv Q2 2026 earnings release, 29 July 2026).
• Vertiv full-year 2026 net sales guidance: 13.8 to 14.2 billion dollars (same release).
• Load swings from synchronized GPU training: 30 to 40 MW within tens of milliseconds (Datacentres.com, unsourced).
• Nvidia's 800 volt direct current design: for racks above 1 MW, starting in 2027 (Nvidia developer blog, company statement).

The three layers of backup, in plain words

When the grid fails, a data center cannot wait for a person to flip a switch. The servers would crash in the first fraction of a second. So backup is built in layers.

Layer one is stored energy. An uninterruptible power supply, or UPS, holds energy in batteries (or, in some designs, a spinning flywheel) and feeds the servers instantly. Most UPS units are also double conversion: they turn incoming AC power into DC and back to AC, which smooths out dips and spikes. The stored energy only lasts a few minutes. The UPS exists to bridge the gap while something else starts.

Layer two is the generator. A diesel generator set, or genset, is an engine driving an alternator. It takes seconds to start and reach speed, and then it can run for as long as it has fuel. A big site has many of them, often in rows, with large fuel tanks.

Layer three is how much duplication you pay for. Engineers use letters to describe this. N is the capacity you need. N+1 means one extra unit. 2N means a full second copy of the whole path. The Datacentres.com article says the effective ratio of generator capacity to load is about 1.4 times with N+1 and about 2.2 times with 2N in hyperscale provisioning. That is its characterization, and it is a reminder that a campus with 100 MW of computing may carry well over 100 MW of generators.

A simple sizing example the same article gives: a 1 MW critical load at a 0.8 power factor needs 1.25 MVA of generator capacity before any redundancy. Power factor is a measure of how efficiently current is used, and it is why the generator rating in MVA is larger than the load in MW.

Generators: how long they take and why

The most detailed primary evidence on generator lead times comes from Generac, a maker of generators that now sells to data centers. On its second quarter 2026 earnings call, held on 29 July 2026, the company said it recognized more than 100 million dollars of data center revenue in the quarter and expected nearly 450 million dollars for the full year. Its data center backlog stood at 1.6 billion dollars, including about 1 billion dollars of new orders in the previous 90 days. About 1.35 billion dollars is scheduled for 2027 delivery and the rest for the second half of 2026. It said it had signed two multi-year hyperscale supply agreements, the first covering nearly 700 million dollars of products for 2027 delivery.

On lead times, management said its own were 40 to 45 weeks and that competitors' were longer, with some systems at 70 to 80 weeks and some packaging constraints. This is a company talking about its own business and its rivals, so treat it as a claim. Still, it fits the broader picture. Generac said it saw a path to tripling large megawatt production capacity over 12 months, with a Sussex, Wisconsin plant starting production by the end of the third quarter of 2026 and a Belvidere, Illinois packaging facility expected to be operating in the first quarter of 2027. Packaging, meaning the enclosure, cooling, controls and fuel systems built around an engine, was named as a constraint.

The Datacentres.com article of 3 September 2026 reports lead times of 18 to 24 months for diesel generators above 2.5 MW, attributed to OEM order books at Caterpillar, Cummins and Kohler. It does not cite a document, and none of those companies has published a lead time in weeks in its own results, so no company specific lead time is given here for them. The 18 to 24 month range (roughly 78 to 104 weeks) sits above Generac's 40 to 80 week range. One possible reason is that Generac and the article describe different engine sizes and different order dates. The public record does not settle which, or whether the gap is real.

The larger engine makers do confirm the demand, even without lead times. Caterpillar's second quarter 2026 results, released on 4 August 2026, put Power and Energy segment sales at 8.238 billion dollars, up 17 percent, with Power Generation sales up 29 percent to 3.098 billion dollars. The company said sales rose in large reciprocating engines and in turbines and turbine related services, "primarily in data center applications." Cummins, reporting the same day, said Power Systems sales rose 19 percent to about 2.3 billion dollars, driven mainly by power generation demand, particularly for data center markets in the US, China and Asia Pacific. Its chief executive, Jennifer Rumsey, credited "robust customer orders for standby power for data centers" for a record quarter. In June 2026 Cummins also agreed to supply natural gas generator sets for a behind the meter microgrid at a Texas computing site run by Circe Energy, with deliveries from 2026 through 2030. That deal is a reminder that some engines bought for data centers are now meant to run as the main power source, not only as backup, which competes for the same factory output.

None of these releases gives a lead time. Rising sales and record orders are consistent with long waits, but they do not measure them.

The same article says standard unit sizes are moving to 3.0 to 3.75 MW, replacing 2.0 to 2.5 MW units, and that a 3.0 MW unit at full load burns 720 to 750 litres of diesel an hour. At that rate it says a 96 hour runtime needs 69,000 to 72,000 litres of storage per generator. It states 96 hours as a typical runtime for the highest reliability tiers, citing NFPA 110 as the baseline, and says hyperscalers are compressing on-site runtime to 48 to 72 hours with resupply within 24 hours. These are the article's statements. Check NFPA 110 and your own reliability tier before using them in a design.

Prices have moved too. The article says large-bore diesel genset installed cost is 450 to 600 dollars per kW, up from roughly 380 to 420 dollars in 2023, and estimates a 100 MW campus at full duplication would spend 99 to 132 million dollars on the generator fleet alone, before fuel systems, land and permitting. It says maintenance on a full-service contract runs 1.5 to 2.5 percent of asset value a year and that quarterly load-bank testing (running generators against a fake electrical load to prove they work) costs 8,000 to 15,000 dollars per unit, up about 20 percent since 2023. None of this is sourced to a document.

UPS and batteries: what is known and what is not

No manufacturer or market operator has published a dated lead time for UPS systems or large battery strings. The Giga article of 13 August 2026 notes that Bloomberg, on 1 April 2026, cited shortages of transformers, switchgear and batteries as a reason data center capacity was delayed, with no duration given. The Bloomberg report itself is not cited here.

The available cost figures come from the Datacentres.com article, again without named sources. It says static double-conversion UPS power electronics, excluding batteries, cost 150 to 250 dollars per kW, and that diesel rotary UPS systems, which store energy in a heavy spinning flywheel coupled to a diesel engine, cost 400 to 600 dollars per kW installed. It says rotary UPS accounts for 8 to 10 percent of new hyperscale AI capacity in 2026, up from under 3 percent in 2023.

On batteries, the article compares two chemistries. VRLA, or valve-regulated lead-acid, is the traditional choice. LFP, lithium iron phosphate, is a common type of lithium-ion battery. The article puts VRLA at 120 to 150 dollars per kWh installed with a 3 to 5 year life, and LFP at 300 to 400 dollars per kWh with a 10 to 15 year life, less floor space and higher round-trip efficiency. It estimates a break-even in year 9 or 10 and a 15 year total cost advantage of 18 to 22 percent for lithium-ion, citing analyses circulating among colocation engineering teams. These are plausible, widely discussed trade-offs. They are not verified numbers, and the break-even depends heavily on replacement cycles and local prices.

Why AI changes the backup problem

A traditional data center load is fairly steady. The Datacentres.com article says synchronized GPU training runs can swing load by 30 to 40 MW within tens of milliseconds. No primary measurement of that figure has been published. The direction is consistent with Nvidia's own writing: its developer blog on 800 volt direct current power says energy storage for load spikes and sub-second GPU power fluctuations is part of its design.

The same Nvidia post explains the bigger shift. Today's racks distribute 54 volts DC inside the rack, a design Nvidia says was made for kilowatt-scale racks. It says racks above 200 kW start to hit physical limits and that a 1 MW rack on 54 volts could need up to 200 kg of copper busbar, which is why it proposes converting 13.8 kV AC grid power to 800 volts DC at the edge of the data center. Nvidia says this starts in 2027 with its Kyber rack systems and lists Eaton, Schneider Electric and Vertiv among data center power system partners. Nvidia's claims of up to 5 percent better end-to-end efficiency and up to 30 percent lower total cost of ownership are its own and not independently tested.

For backup power this matters because an 800 volt design changes where batteries and fast storage sit, and may change which UPS products are needed. It does not remove the need for generators.

Who supplies what

The sources below name these companies.

• Generators: Generac (with its own earnings figures above); Caterpillar and Cummins, whose August 2026 results tie power generation growth to data centers; and Kohler, named with the other two by Datacentres.com as holding the order books that set large generator lead times.
• Power equipment and UPS-related products: Eaton, Schneider Electric and Vertiv are named by Nvidia as data center power system partners. Eaton's July 2026 filing says its Electrical Americas segment includes Fibrebond, a builder of modular power enclosures for data centers, and Resilient Power Systems, which makes solid-state transformer technology.
• Vertiv's financial picture: its second quarter 2026 release shows net sales of 3,274.3 million dollars, up 24.1 percent, and says revenue reflected minor timing shifts, primarily from temporary supply chain congestion and multi-phased project execution. Its inventories rose by about 1.07 billion dollars between December 2025 and June 2026. The release does not say what the inventory is.

This is a list of names that appear in the cited sources, not a ranking or a market share table.

What is firm and what is uncertain

Firm enough. Generator demand from data centers is strong enough that one maker has a 1.6 billion dollar data center backlog and is tripling plant capacity, and the two largest engine makers both attribute power generation growth to data centers in their own results. Delivery waits for large units are measured in many months to a couple of years. Backup systems are designed in layers with duplication.

Uncertain. Competitor generator lead times are a company claim. The 18 to 24 month range, the cost per kW, the battery costs and the duty cycle numbers come from an article that does not name sources. No primary source gives UPS and battery lead times. The rise in Vertiv inventory has no stated cause.

What to watch next

• Generac's third quarter call for backlog, lead times and the Sussex ramp.
• Caterpillar and Cummins third quarter results, and whether either starts to publish lead times or order backlog for large generators.
• Early 800 volt direct current deployments in 2027 and what they do to UPS and battery design.
• Whether on-site fuel runtime targets fall and resupply contracts take their place.
• Any published, sourced lead times for UPS and large battery systems.

Related reading: how the power gear upstream is supplied and what Anthropic's compute commitments include.

Safeguard does not sell power equipment, but it can scan the dependencies of software that monitors it and build an SBOM, and there is a free scan at https://gold.safeguard.sh/scan.

Quick check

Sources

• Generac Q2 2026 earnings call transcript, 29 July 2026 (Motley Fool): https://fool.com/earnings/call-transcripts/2026/08/07/generac-gnrc-q2-2026-earnings-call-transcript
• Datacentres.com Research, Diesel, duty cycles and dollars: inside the 2.8M per MW backup power stack, 3 September 2026: https://www.datacentres.com/news/diesel-duty-cycles-and-dollars-inside-the-2-8m-per-mw-backup-power-stack-powerin-slot3-2026-09-03
• Vertiv Q2 2026 results release, 29 July 2026: https://investors.vertiv.com/news/news-details/2026/Vertiv-Reports-Strong-Second-Quarter-2026-with-Diluted-EPS-Growth-of-53-Adjusted-Diluted-EPS-Growth-of-60-Raises-Full-Year-2026-Guidance-Across-All-Key-Metrics/default.aspx
• Eaton Form 8-K exhibit, second quarter 2026 results: https://www.sec.gov/Archives/edgar/data/0001551182/000155118226000027/etn06302026exhibit99.htm
• Nvidia developer blog, 800 V HVDC architecture for AI factories: https://developer.nvidia.com/blog/nvidia-800-v-hvdc-architecture-will-power-the-next-Generation-of-ai-factories
• Giga, Lead time delays for data centers, 13 August 2026: https://www.gigaenergy.com/blog/lead-time-delays-for-data-centers
• Caterpillar Form 8-K exhibit 99.1, second quarter 2026 results, 4 August 2026: https://www.sec.gov/Archives/edgar/data/0000018230/000001823026000040/ex991toformcat2q2026earnin.htm
• Cummins, Cummins Reports Strong Second Quarter 2026 Results; Raises Full-Year Outlook, 4 August 2026: https://investor.cummins.com/news/detail/701/cummins-reports-strong-second-quarter-2026-results-raises

Last reviewed: 19 October 2026.