Quick Presets

Use Case

Power & Energy

Peak Discharge Power (kW)

Discharge Duration (hours)

Chemistry & Operation

Cell Chemistry

Depth of Discharge (%)

Ambient Temperature (°C)

Project Parameters

Project Life (years)

Capacity Guarantee (%) Minimum SOH at end-of-project (typically 80%)

Email Report

IEC 62933-2-1 IEEE 2030.2.1 IEC 62660-1 NFPA 855 UL 9540A

Enter parameters and click Size BESS System to size your BESS system.

Sizing Results

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kWh
Nameplate Energy

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kWh
Nameplate with Headroom

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PCS Rating

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C-Rate

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Round-Trip Efficiency

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kWh

Year-1 Usable Energy

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kWh

Year-10 Usable Energy

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× 40ft

Footprint (40ft containers)

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cycles

Cycle Life

Efficiency Breakdown

State of Health Trajectory

Augmentation Schedule

Recommendations

Methodology

Quantity	Formula	Standard
Usable energy	E_usable = P_max × t_h	IEC 62933-2-1
Nameplate	E_np = E_usable / (DoD × η_disch)	IEC 62933-2-1 §6
RTE net	η_rte = η_chg × η_dis × T_rte × (1 − η_aux)	IEEE 2030.2.1
Cycle life (DoD)	N(DoD) = N_ref × (80%/DoD)^α	IEC 62660-1
Arrhenius factor	k = exp(E_a/R × (1/T_ref − 1/T))	IEC 62933-2-1
SOH decay	SOH = exp(−λ_cyc×N) × exp(−r_cal×k×yr)	IEC 62660-1
Headroom	E_np,hw = E_usable / (DoD × η_dis × SOH_guarantee)	IEEE 2030.2.1

Frequently Asked Questions

What is round-trip efficiency (RTE)? +

RTE is energy-out / energy-in over a full charge–discharge cycle, including HVAC parasitic losses. LFP at 25°C typically achieves 88–92% net RTE per IEC 62933-2-1.
Why do I need to oversize the nameplate? +

Batteries degrade over time (cycle wear + calendar aging). The "nameplate with headroom" factors the capacity guarantee threshold into sizing, so usable energy at end-of-life still meets your requirement.
What is augmentation vs. overbuild? +

Overbuild installs extra capacity upfront. Augmentation adds capacity later at points where SOH drops below the guarantee. Augmentation has lower capex today but higher O&M risk; overbuild is simpler but ties up more capital.
How does the cycle life model work? +

This tool uses an Arrhenius calendar aging model combined with a power-law DoD cycle-wear model (N ∝ (80%/DoD)^α). Parameters are calibrated to IEC 62933-2-1 typical values for LFP, NMC, and LTO chemistries.
What is a C-rate? +

C-rate = peak power (kW) / nameplate energy (kWh). A 1C rate fully charges/discharges in 1 hour. LFP supports up to 2C continuously; LTO supports up to 10C. Exceeding the max C-rate risks accelerated degradation or cell damage.
Which chemistry should I choose? +

LFP offers the best cycle life and thermal safety for stationary storage. NMC has higher energy density (smaller footprint). LTO suits applications requiring many daily cycles or fast charge (FCR, PV smoothing).

BESS Capacity & Round-Trip Sizing