How long can the Bluetti AC500 + B300S run a CPAP machine?
8.2 dayswell beyond what you asked for
Formula: (3.1kWh × 0.85 inverter efficiency) ÷ 0.32 kWh/day = 8.2 days. At continuous 40 W draw (no duty cycle), about 2.7 days.
What if you add a battery? The AC500 + 2× B300S config jumps to 6.1kWh — roughly 16.3 days on a CPAP machine.
Appliance
CPAP machine · 40 W / 60 W surge
Battery (base)
3.1kWh · 5kW / 10kW surge
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Runtime Quick-Check
Runtime Quick-Check
Pick a battery and an appliance — see days of runtime after the 0.85 inverter derate.
8.2 days
Formula: (3072 Wh × 0.85) ÷ 0.32 kWh/day = 8.2 days. Continuous draw ≈ 2.7 days at full load.
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