How to use this calculator
- Enter the electrical demand the system must serve.
- Add the project-specific reserve margin.
- Enter the expected available-output percentage.
- Set a standard unit size and calculate the rounded installation.
#1220 · Energy & Environment Tool
Microgrid System Sizing Calculator
Estimate preliminary rated power for a microgrid from required electrical output, reserve margin, expected derating, and standard unit size. The result gives both continuous calculated capacity and a whole-unit installation size, useful for early feasibility comparisons before detailed engineering of redundancy, energy supply, protection, and transient performance.
Calculator
Project inputsFormula
Required rated MW = Demand × (1 + Reserve margin) ÷ Available-output fraction
Whole units = round up(Required rated MW ÷ Unit size)
Whole units = round up(Required rated MW ÷ Unit size)
What the result means
Calculated rated capacity is the minimum nameplate power under the entered assumptions. Rounded installed capacity reflects indivisible equipment modules.
This is a screening calculation, not an electrical design. Verify N+1 criteria, fault current, dynamic response, fuel or energy availability, and applicable codes.
Example calculation
For 4 MW demand, 20% reserve, and 90% available output, calculated capacity is 5.33 MW. With 0.5 MW units, round up to 11 units or 5.50 MW installed.
Tips for better results
- Size against coincident demand, not summed peaks.
- Document the basis for reserve margin.
- Use site-condition derating data.
- Check N+1 operation separately.
- Confirm energy supply and duration after power sizing.
Frequently asked questions
Why divide microgrid demand by the derating percentage?
Derating means each rated MW is expected to provide less than one available MW, so more nameplate capacity is needed.
How should I choose the reserve margin?
Use the project reliability criterion, forecast uncertainty, and contingency requirement rather than a generic benchmark.
Why are whole units rounded up?
Partial equipment modules generally cannot be installed, and rounding down would leave the design below the calculated requirement.
Does this size include energy storage duration?
No. It sizes power capacity only; energy or fuel inventory must be checked separately.
Can this replace detailed system engineering?
No. Protection, interconnection, redundancy, dynamic stability, and equipment constraints require qualified engineering.
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Formula variables and units
| Variable | Meaning | Unit |
|---|---|---|
| D | Required served electrical demand | MW |
| M | Additional design reserve | % |
| F | Expected available output per rated MW | % |
| U | Standard indivisible unit size | MW |