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Use the free estimator for a preliminary layout, or share your preferred response method with the commercial team. Final feasibility still requires site, utility, and engineering review.
Start with the business function that cannot stop—not a battery model number. Define the coincident critical-load kW, required runtime, transfer sequence, restart behavior, and state-of-charge policy before selecting power and energy.
Add the loads that must run at the same time to establish critical kW, check motor and compressor starts against inverter surge and controls, then multiply the expected critical load by the outage hours you need. Adjust the energy result for usable state of charge, efficiency, temperature, aging, and reserve. The battery also needs an approved islanding and transfer design; a grid-tied battery without that equipment shuts down with the grid.
Two independent constraints
The inverter must serve the largest coincident running load and the permitted starting behavior of motors, compressors, pumps, and transformers. Sequenced starts and load shedding can reduce the required kW; an uncontrolled simultaneous restart can exceed it.
Usable energy—not nameplate energy—sets runtime. Reserve policy, battery age, temperature, auxiliary loads, and conversion losses reduce what reaches the backed-up bus. Cycling loads need a time-weighted duty cycle rather than full nameplate draw for every hour.
A runtime quotient is only a screen. Final design must simulate the actual load sequence, inverter operating envelope, battery warranty limits, low-temperature performance, state-of-charge floor, and restart controls.
An electrical one-line tells you what is connected. An operating interview tells you what actually matters. Record running kW, start behavior, duty cycle, maximum interruption, and consequence of failure for every candidate load.
Cold rooms, freezers, pumps, environmental control, alarms
Ask: What inventory or process loss begins when temperature or pressure drifts?
Network, servers, point of sale, access control, communications
Ask: Which systems must bridge until shutdown, generator start, or full restoration?
PLCs, controls, instrumentation, selected motors and conveyors
Ask: Which sequence must finish safely, and which loads can be shed first?
Egress lighting, fire and life-safety interfaces, medical or accessibility loads
Ask: Which loads are code-required, operationally critical, or both?
Power path
The approved design must isolate the facility from the utility, energize a defined island, coordinate protection, and control which source serves which bus. The exact one-line varies by service and equipment; the relationship below is the owner-side concept to verify.
Utility + on-site sources
Grid, solar, generator where present
Grid-forming battery + isolation
PCS, switchgear, protection, EMS
Backed-up bus
Defined loads and shedding sequence
| Owner objective | Design emphasis | Proof before acceptance |
|---|---|---|
| Bridge short interruptions | Fast transfer, high power, enough energy for controlled ride-through | Transfer test under the real critical load |
| Carry defined loads for hours | Critical-load panel or backed-up bus, load shedding, usable-energy reserve | Time-series outage simulation plus commissioning test |
| Peak shave and provide backup | State-of-charge floor and priority logic across bill, program, and outage objectives | EMS dispatch simulation across interval data and program events |
| Cover long or uncertain outages | Battery plus solar and/or generator, fuel strategy, black-start and recharge sequence | Multi-day resilience scenario and islanded controls test |
Ask bidders to identify the listed system, fire-test evidence, adopted code basis, separation and access assumptions, ventilation or gas-detection strategy where applicable, emergency operations plan, first-responder coordination, and the authority-having-jurisdiction review path.
A reference is not an approval. The adopted electrical, fire, building, and interconnection requirements—and the authority having jurisdiction—control the project.
Build a critical-load schedule first. Battery power in kW must cover the coincident running load and permitted motor-start behavior; usable battery energy in kWh must cover the desired runtime after reserve, temperature, aging, and conversion losses. Then verify the transfer architecture, service configuration, protection, and controls with the engineer and authority having jurisdiction.
Bring the one-line, interval data, critical-load schedule, outage objective, and any generator or solar constraints. We will review the operating sequence before equipment selection.