A “300 W” portable power station rating mainly describes how much power it can deliver at one time, not how long it runs. The runtime mostly depends on its battery capacity (measured in watt-hours, or Wh), the wattage of what you plug in, and normal conversion losses.
Use this simple estimate: Runtime (hours) ≈ Battery Wh × 0.85 ÷ Device watts. The 0.85 factor accounts for typical inverter and conversion losses (often 10–20%). For example, if a 300 W unit has a 280 Wh battery, usable energy might be around 238 Wh (280 × 0.85).
Many 300 W portable power stations fall roughly in the 250–320 Wh capacity range (always check the spec sheet). With that in mind, here are common scenarios:
Phone charging (10–15 Wh per full charge): Often around 12–20 full charges, depending on phone size and charging losses.
Laptop (50–70 W while running/charging): About 3–5 hours of continuous draw, or several partial recharges depending on the laptop battery.
Wi-Fi router (10 W): Roughly 20–27 hours.
LED light (5–10 W): Roughly 20–50 hours, depending on brightness and exact wattage.
Small fan (20–40 W): Around 5–13 hours.
A 300 W station can usually run devices up to 300 W (sometimes more for surge), but a high-watt device drains the battery quickly. For instance, a 250 W load can empty a 280 Wh battery in close to an hour once losses are included.
Keep loads low, prefer DC/USB outputs when possible, and avoid running heated appliances (space heaters, kettles, hair tools), which can exceed the watt rating and/or drain the battery fast. If the goal is efficient charging, this guide on compact charging gear is a helpful companion: https://ultimatechoicespoint.shop/guide-30w-power-bank-for-apple-fast-iphone-ipad-charging/.
It can typically run low-to-mid watt electronics like phones, tablets, laptops, routers, lights, and small fans. High-heat appliances and many cooking devices usually draw too many watts to be practical (or may exceed the limit).
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