Battery Storage Sizing Planner
Convert required usable energy into nominal kWh and Ah after depth-of-discharge and efficiency assumptions.
Use the Battery Bank Calculator
Convert required usable energy into nominal kWh and Ah after depth-of-discharge and efficiency assumptions.
Calculations happen locally in your browser. ToolLott does not send these inputs to a server for this tool.
Preliminary engineering calculation only. It does not replace applicable codes, manufacturer data, licensed electrical or mechanical design, protection studies, derating, fault checks, site conditions or professional verification.
How to use it
Replace the worked-example values with the actual project inputs. Review the intermediate quantities and assumptions before using the result elsewhere.
How the Battery Bank Calculator works
Convert required usable energy into nominal kWh and Ah after depth-of-discharge and efficiency assumptions. The methodology below exposes the production equation, a QA-verified worked example and the boundary between this screen and detailed design.
Calculation breakdown
ToolLott will explain the current inputs and displayed result here.
Battery-bank nominal energy from usable-energy target
The production engine evaluates nominal kWh = usable kWh / DoD / efficiency; Ah = nominal kWh x 1000 / voltage. It begins by convert depth of discharge and efficiency to decimal fractions., then divide the usable-energy requirement by both fractions to obtain nominal energy., and finally convert nominal kWh to amp-hours at the entered bank voltage. This keeps the calculation auditable instead of hiding design assumptions behind a single number.
nominal kWh = usable kWh / DoD / efficiency; Ah = nominal kWh x 1000 / voltageToolLott evaluates the relationship using the entered units and full numeric precision before display rounding.
| Symbol / input | Meaning | Unit |
|---|---|---|
usable | Required usable energy (kWh) | user input |
voltage | Battery system voltage (V) | user input |
dod | Maximum depth of discharge (%) | user input |
efficiency | System efficiency (%) | user input |
Step-by-step method
- Convert depth of discharge and efficiency to decimal fractions.
- Divide the usable-energy requirement by both fractions to obtain nominal energy.
- Convert nominal kWh to amp-hours at the entered bank voltage.
Worked example
Noah, a project engineer, needs 12 kWh of usable overnight energy from a 48 V battery system and intends to limit depth of discharge to 80%.
Example inputs
- Required usable energy (kWh): 12
- Battery system voltage (V): 48
- Maximum depth of discharge (%): 80
- System efficiency (%): 100
Calculation / processing
Nominal energy = 12 / 0.80 / 1.00 = 15 kWh.Energy in watt-hours = 15,000 Wh.Capacity = 15,000 / 48 = 312.5 Ah.
Use the result as a screening or quantity-planning value and compare it with the project criteria, manufacturer data and applicable engineering requirements before making a design or procurement decision.
Assumptions
- The entered values are representative of the condition being screened and use the units shown on the page.
- The equation models only the stated relationship; omitted system effects are not silently estimated.
Limitations
- This page is not engineering certification and does not replace applicable standards, design loads, manufacturer data, site investigation or competent professional review.
- Results can change materially when real geometry, losses, transients, material properties, duty cycles, safety factors or regulatory criteria differ from the simplified inputs.
Common questions
Is this a final engineering design?
No. It is a transparent screening calculation using the entered assumptions and the stated equation.
Why does the page show assumptions and limitations?
Engineering formulas are only valid within their modelling assumptions; exposing them helps users decide what additional design checks are required.
Should I use the rounded displayed value in later design work?
Use suitable calculation precision and the governing project/standard requirements rather than relying on display rounding alone.
Methodology sources
Related ToolLott tools
A realistic way Noah could use this tool
Noah is a project engineer.
Noah needs 12 kWh of usable overnight energy from a 48 V battery system and intends to limit depth of discharge to 80%.
Noah fills the tool with the case values—usable = 12; voltage = 48; dod = 80; efficiency = 100. Running those values produces Nominal battery capacity: 15 kWh, giving the scenario a concrete output that can be recalculated or regenerated when the inputs change.
The resulting figure/text/output is Nominal battery capacity: 15 kWh. Noah now has a reproducible checkpoint for the task: 12 kWh of usable overnight energy from a 48 V battery system and intends to limit depth of discharge to 80%. The page also keeps this limitation explicit: Preliminary screening or quantity calculation only.
Fictional scenario using realistic example data. For Ready tools, the worked result is tied to the tested example shown in the tool. Replace the figures with your own inputs and independently verify important professional, financial, legal, health or safety decisions.
What this calculator is for
Use it to convert required usable energy into nominal kWh and Ah after depth-of-discharge and efficiency assumptions.
It sits within ToolLott’s Electrical collection, where you can also estimate battery banks, cable sizes, generator sizes, motor current, Ohm’s law values, solar systems, transformers and voltage drop.
Battery Storage Sizing Planner
Start from the energy you actually need, then account for usable depth, system efficiency and nominal battery voltage.
Real battery selection also depends on peak power, temperature, cycle life, BMS limits, inverter compatibility and manufacturer specifications.