Most portable chargers can top up a phone. Very few can charge a laptop. The ones that can are larger, more expensive, and worth it if you work away from outlets regularly. I have killed two laptops by letting them die to zero percent while working from coffee shops and airport gates. A laptop-compatible power bank would have prevented both deaths.

The spec that actually matters: wattage

Forget milliamp-hours for a moment. The number you need to look at is watts of power delivery. A standard phone charger outputs about twelve to twenty watts over USB-C. A laptop needs at least forty-five watts, and most need sixty or sixty-five watts to charge while you are using them. A power bank that outputs thirty watts will not charge your laptop — it will only slow down how fast the battery drains.

Look for a power bank labeled “65W PD” or higher. PD stands for Power Delivery, which is the USB-C fast-charging standard that both phones and laptops use. If it does not say PD or only lists Qualcomm Quick Charge, it is not for laptops.

Capacity: how many charges you actually get

A power bank rated at twenty thousand milliamp-hours (20,000mAh) sounds enormous. But that rating is at the battery’s internal voltage — usually 3.7 volts. When converted to the twenty volts that a laptop USB-C port uses, the actual capacity is closer to about forty watt-hours. A typical laptop battery is fifty to sixty watt-hours. So a “20,000mAh” power bank gives you roughly two-thirds of a full charge on a thirteen-inch laptop, or about one full charge on a tablet.

For a full laptop charge, get a power bank rated at 26,000mAh or higher. The Anker 737 (24,000mAh, 140W output) and the Baseus 65W 20,000mAh are the two I have used and both deliver what they promise. The Anker charges faster — it can refill itself in about an hour — but costs more. The Baseus is lighter and cheaper but charges slower.

What you cannot charge

Gaming laptops and large workstation laptops with dedicated GPUs draw a hundred watts or more. Most portable power banks cannot keep up with those. If your laptop charger brick is larger than a deck of cards, check its wattage rating. If it is over one hundred watts, a portable power bank is probably not going to work for you. You would need a portable power station — the kind with an AC outlet — and those are a different product category entirely.