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The monthly generator load test: the 30% / 30-minute rule
General overview — verify against the governing code and your AHJ. The intervals and requirements described here reflect a good-faith reading of NFPA 110 / CMS Life-Safety requirements and can vary by code edition, jurisdiction, accreditor, and equipment. This is not legal or engineering advice and may not be the exact requirement for your facility — always confirm the tests and intervals that apply to you with your Authority Having Jurisdiction (AHJ) and accreditor. StandbyProof readies your records; it does not determine your requirements.
The monthly load test is the requirement facilities miss most — usually not by skipping it, but by testing outside the window or running under-loaded. Here's exactly what it asks for.
Educational overview only. Not compliance advice and not your Authority Having Jurisdiction. Your AHJ, accreditor, state amendments and equipment manufacturer may set different requirements. Confirm your facility's specifics with your compliance officer.
What the monthly test generally calls for
- Interval: every 20–40 days (not just "monthly" — the window is what matters).
- Duration: at least 30 minutes of running.
- Load: at least 30% of the generator's nameplate kW rating, or the manufacturer's specified exhaust-gas temperature.
- Cold start: the test should include a cold start.
- Record it: capture duration, load, and result — that record is your proof at survey time.
The under-load trap
Many installed generators are oversized for their real emergency load, so a monthly test naturally runs below 30% of nameplate. When that happens, NFPA 110 generally requires a supplemental annual load-bank test to a step schedule to make up the difference. If you're not tracking the load percentage each month, you may be accruing a load-bank obligation without realizing it.
Frequently asked questions
- How long does the monthly load test run?
- At least 30 minutes at ≥30% nameplate load, including a cold start.
- What if I can't hit 30% load?
- A supplemental annual load-bank test is generally required to make up for under-loaded monthly runs.
- Is it once a month or every 20–40 days?
- Every 20–40 days. Calendar-month timing can drift out of the window, so track the actual interval.
Stop tracking load-test windows in a spreadsheet
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