Generator sizing — running watts plus the single largest surge

Add every running watt but only the single largest starting surge, then add ~25% headroom — adding every surge overshoots badly.

A stacked bar shows a generator size: 5,000 watts of running load, plus a single 3,500-watt starting surge (only the largest motor surges at once), for an 8,500-watt peak, plus 25 percent headroom, giving about an 11 kW recommended generator. A faint red ghost bar shows how adding every appliance surge together would badly overshoot. — Source: Manufacturer load charts; 20–25% headroom guidance

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A stacked bar shows a generator size: 5,000 watts of running load, plus a single 3,500-watt starting surge (only the largest motor surges at once), for an 8,500-watt peak, plus 25 percent headroom, giving about an 11 kW recommended generator. A faint red ghost bar shows how adding every appliance surge together would badly overshoot.

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    <img src="https://remodelcalculators.com/api/figure-embed/generator-running-plus-surge" alt="A stacked bar shows a generator size: 5,000 watts of running load, plus a single 3,500-watt starting surge (only the largest motor surges at once), for an 8,500-watt peak, plus 25 percent headroom, giving about an 11 kW recommended generator. A faint red ghost bar shows how adding every appliance surge together would badly overshoot." width="800" height="460" style="width:100%;height:auto;border:0" loading="lazy">
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    Diagram: <a href="https://remodelcalculators.com/construction-diagrams/generator-running-plus-surge" target="_blank" rel="noopener">Generator sizing — running watts plus the single largest surge</a> — courtesy of <a href="https://remodelcalculators.com" target="_blank" rel="noopener">RemodelCalculators.com</a>
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