Power
The Load Behind a UPS Runtime Estimate
Compare a UPS runtime offer at the required load, with its stated UPS, battery configuration and estimate conditions. Power capability describes a rate of supply; stored energy describes a quantity; runtime describes how long the stated load is estimated to be supplied. A duration headline cannot travel unchanged to a different load. The Easy UPS 3L example below shows why converting one published estimate into an energy quantity also does not establish a fixed reserve for another load.
Separate power capability, stored energy and duration
The U.S. Energy Information Administration distinguishes storage power capacity, expressed in units such as kW, from energy capacity, expressed in units such as kWh. Power concerns the rate of supply. Energy concerns an amount stored or discharged. A UPS capability figure and a battery energy figure therefore answer different questions.
Duration connects energy to a particular demand. For a constant load, multiplying kW by hours gives the energy supplied to that load over the interval. Dividing an energy quantity by a load gives a duration only if that quantity is assumed to be available to that load. The arithmetic does not establish the assumption.
The load also needs a consistent boundary. A figure for selected IT equipment and a figure including additional supported equipment describe different demands. Comparing their backup minutes as though they represented the same load would leave the buyer's requirement unresolved.
Keep the exact configuration attached to the estimate
Schneider Electric's Easy UPS 3L 250–600 kVA Technical Specifications, edition 990-6289H-001, presents runtimes as estimates based on battery-manufacturer data at 25 °C. In its 250 kVA, power-factor-1 table, the E3MCBC10D row lists 36.5 minutes at 25% load and 15 minutes at 50% load.
On that stated power-factor-1 basis, the two load points are 62.5 kW and 125 kW. The percentages are fractions of the named UPS rating, rather than independent descriptions of a battery. Keep the UPS rating, row identifier, load and conditions together when carrying either estimate into a quotation comparison.
References: [UR1]
See why one fixed energy allowance misses the second estimate
Use those two points as constant-load arithmetic. The first product is 62.5 kW × (36.5/60) hours = approximately 38.02 kWh. The second is 125 kW × (15/60) hours = 31.25 kWh. These are calculated load-side energy amounts over the estimated intervals. Neither is a nominal battery-capacity specification or a measured discharge result.
Now add an assumption: treat the first product as a fixed energy allowance available at the higher load. That predicts 36.5 × 62.5/125 = 18.25 minutes. The matching published estimate is 15 minutes. The fixed allowance therefore does not reproduce both manufacturer estimates.
The distinction matters when a quotation turns one duration into a supposed usable-kWh reserve and then scales that reserve across loads. Correct units cannot rescue an unsupported fixed-energy assumption. Here, the two documented load-duration pairs already provide a better basis for comparing the two stated demands.
The mismatch establishes that limit on the calculation. It does not identify a loss mechanism or supply a general battery model. There is no basis here for allocating the difference to a particular cause.
Resolve a 15-minute requirement at 125 kW
Consider a fictional buyer comparing two offers against a stipulated requirement: 15 minutes at a constant 125 kW, using the exact configuration and estimate conditions above. This is a comparison of quotation evidence; the requirement is an example, rather than a recommended duration or equipment choice.
The buyer's comparison sheet initially places an offer headed 36.5 minutes of backup ahead of an offer stating 15 minutes at 125 kW. The longer headline looks more generous, but its load is missing. At this stage, it has not answered the buyer's duration question.
The second offer identifies the matching manufacturer cell. Its 15-minute estimate equals the stipulated 15-minute requirement. That resolves the numerical comparison at the required load. It shows no additional estimated minutes beyond that requirement.
Suppose the first supplier then clarifies that its headline refers to the lower load and confirms the same configuration and the same 125 kW estimate as the second offer. The buyer can now compare them on the same basis: their cited duration evidence is equal. The longer headline did not establish a longer duration at the required load, and the shorter headline did not establish inferior battery capability.
The fixed-energy shortcut would have entered 18.25 minutes for the first offer. Using the matching cell instead removes 3.25 minutes of unsupported apparent surplus. It also avoids comparing the lower-load headline directly with the higher-load requirement.
References: [UR1]
Keep a numerical match within what the evidence answers
The matching cell answers how the stated estimate compares with the stipulated duration. It leaves the actual installation's battery condition, delivered-load history and continuity during a facility event unobserved. Schneider's applicability text also distinguishes its general product information from application-specific suitability. Actual electrical design, suitability and acceptance remain with the customer's appointed qualified facility, electrical and OEM parties.
For a real offer, ask the supplier to connect its duration claim to the exact supplied configuration, the required load and the applicable estimate conditions. If those differ from this example, the useful answer is evidence addressing those conditions. A value carried from another load does not fill that gap.
Runtime is one part of the purchasing decision. The related UPS/BESS guide owns the separate continuity and reserve-allocation questions. The bypass guide addresses the supply path and battery support in the stated operating mode. Keeping those questions with their evidence prevents a correct duration comparison from becoming an unsupported claim about the whole power arrangement.
References: [UR1]
Bring the selected equipment into the physical IT scope
After the customer has selected supported equipment and the appointed facility parties have established the relevant interfaces, the physical IT package can identify the rack positions, requested installation tasks and site restrictions. The site-readiness guide provides context for that handoff.
Use the related rack-and-stack service and project inquiry to discuss separately agreed IT equipment mounting, IT cabling, labeling and installation records, subject to scope, site requirements and availability. Share the selected IT equipment and requested physical work so the inquiry concerns an identifiable installation package.
Primary sources
- [UR1] Schneider Electric — Easy UPS 3L 250–600 kVA Technical Specifications: Battery Runtimes, 990-6289H-001Checked 2026-10-20. The E3MCBC10D example uses the named UPS rating and the table's stated estimate conditions. Useful for comparing documented duration claims at specified loads; it does not determine application suitability.
- [EIA1] U.S. Energy Information Administration — Energy storage for electricity generationChecked 2026-10-20. The capacity definitions distinguish power in watts from energy in watt-hours. Used for terminology, without transferring grid-storage statistics or performance assumptions to a UPS.
- [EIA2] U.S. Energy Information Administration — Measuring electricityChecked 2026-10-20. The power and energy-over-time explanation supports the units in the constant-load arithmetic. It provides no battery-capacity or UPS-runtime specification.