What size power bank do I actually need?

For most people, a 20,000 mAh power bank is the practical sweet spot. It charges a typical smartphone three to four times, still fits in a bag, and stays under the FAA's 100 watt-hour carry-on limit. A 5,000 to 10,000 mAh bank works as a pocket top-up for a single day. Above about 27,000 mAh you cross the 100 Wh line that airlines care about, so if you fly regularly, check the watt-hour rating printed on the bank rather than the milliamp-hour number.

What is the difference between mAh and watt-hours on a power bank?

Milliamp-hours (mAh) measure the raw cell capacity at the cell's native voltage, typically 3.6 to 3.7 volts. Watt-hours (Wh) factor in voltage, giving a true measure of stored energy. The conversion is: mAh times voltage divided by 1,000 equals Wh. A 20,000 mAh bank at 3.6V holds about 72 Wh. Watt-hours are the number that matters for comparing banks, sizing for devices, and checking airline limits.

Can I bring a power bank on a plane?

Yes, in your carry-on only. The FAA requires all spare lithium batteries and power banks to travel in the cabin, never in checked baggage. Banks under 100 Wh need no airline approval. Banks between 101 and 160 Wh require airline approval and are limited to two per person. Anything over 160 Wh is prohibited. As of May 2026, several major US carriers added their own stricter rules, including limits on the number of banks per passenger and prohibitions on charging them or storing them in overhead bins during flight. Check your specific carrier before traveling.

How long does a power bank last before it wears out?

Most lithium-ion power banks are rated for 500 to 1,000 charge-discharge cycles before capacity drops noticeably, typically to about 80 percent of original capacity. At one full cycle per day that is roughly two to three years of heavy use. In practice, most households cycle a bank once a week or less, which means five or more years of useful life. Heat, deep discharges, and long periods stored fully charged or fully empty shorten lifespan. Keeping a standby bank between 40 and 80 percent charge in a cool place is the simplest way to preserve it.

Should I get a solar power bank or a regular one?

For most households, a regular power bank paired with a separate folding solar panel is a better investment than a solar-integrated bank. The small panels built into solar power banks generate very little current, often requiring multiple full days of direct sunlight to fully recharge the bank. A dedicated 20 to 30 watt folding panel recharges the same bank in a few hours. Solar-integrated banks make sense as a backup when you have no other charging option and weight matters, but they should not be your primary recharging plan.

Buyer's Handbook

Battery banks, explained before you spend.

A power bank is the simplest piece of backup power a household can own. This handbook explains what the numbers on the box really mean, which type fits your situation, and the one spec that decides whether you can fly with it.

Reviewed September 2026. We re-check this guide quarterly.

Start here

The device you will reach for first

The power goes out. Your phone has 30 percent left. You need it for weather alerts, for calling family, for the flashlight app until you find the real flashlight. A power bank sitting in a drawer, already charged, buys you another day of phone use without thinking about it.

Outside of outages, a power bank is just as practical: a long day away from a charger, a road trip, a campsite, a waiting room. It is one of the few pieces of preparedness gear that earns its keep in everyday life, which is why it is usually charged when you actually need it.

The market is full of them, the specs are confusing, and the numbers on the packaging do not mean what most people think they mean. This guide sorts the field by what actually matters to a household buying one.

Before you buy

Four questions about your own household

Answer these before you look at a single product. They narrow the field more than any brand comparison does.

What devices are you charging?

A phone needs about 10 to 20 Wh per charge. A tablet needs 30 to 45 Wh. A laptop needs 50 to 100 Wh and requires USB-C Power Delivery. Knowing your devices sets the minimum capacity and output you need.

How long without grid power?

A single power bank covers a day or two of phone use. More than that and you either need a high-capacity bank, a way to recharge it (solar panel, car adapter), or you are looking at a portable power station instead.

Portability or capacity?

A pocket-size 5,000 mAh bank is always with you. A 20,000 mAh bank is a bag item. A 30,000 mAh bank is heavier than some laptops. There is no bank that is both pocket-size and high-capacity.

Do you fly with it?

The FAA caps spare lithium batteries at 100 Wh without approval. That is roughly 27,000 mAh. If air travel is part of your life, this number sets your ceiling. As of May 2026, several US carriers added their own stricter limits on top of the FAA rule.

How it works

A battery in a box, with rules

A power bank is a set of lithium-ion or lithium-polymer cells wired to a circuit board that manages charging and discharging. The cells store energy at their native voltage (typically 3.6 to 3.7V) and the circuit converts that up to 5V or higher when your phone or device draws from it. That conversion is where the advertised capacity and the delivered capacity diverge, and understanding the gap is worth more than knowing any brand name.

The circuit board does several things: it prevents overcharging, cuts off when the cells are depleted, manages heat, and negotiates with connected devices about how much power to deliver. In banks that support USB-C Power Delivery, this negotiation can push output to 20V or higher, which is what allows a power bank to charge a laptop. The quality of this circuit board matters more than the raw cell capacity, because a poor circuit wastes more energy as heat and delivers less to your device.

One consequence: every power bank loses energy in the conversion. A bank rated at 20,000 mAh holds about 72 to 74 Wh at the cell level, but delivers roughly 50 to 55 Wh to your device. The rest leaves as heat. This is normal physics, not a defect, and it is why no 20,000 mAh bank charges a 5,000 mAh phone four times. Three full charges is the realistic number.

The numbers decoded

mAh vs. Wh: the one distinction that matters

Manufacturers put the milliamp-hour (mAh) number in large print because it is always the bigger number. But mAh describes charge capacity at one voltage, and different banks use different voltages. Watt-hours (Wh) factor in voltage, making it the only honest way to compare two banks or to check whether yours meets an airline limit.

The conversion: multiply mAh by voltage, divide by 1,000. Most consumer power banks use cells at 3.6V or 3.7V. A 20,000 mAh bank at 3.6V holds 72 Wh. A 26,800 mAh bank at 3.7V holds 99.16 Wh, which is why that number appears on so many "maximum airline-legal" models.

mAh rating	Approx. Wh (at 3.6V)	Usable phone charges	Airline status
5,000	18 Wh	~1	No restrictions
10,000	36 Wh	~2	No restrictions
20,000	72 Wh	~3	No restrictions
26,800	~99 Wh	~4	Under 100 Wh limit
30,000+	108+ Wh	~5+	Airline approval required

Usable phone charges assume a typical modern smartphone with a 4,500 to 5,000 mAh battery and 20 to 35 percent conversion loss. Your actual number will vary with cable quality, device charging protocol, and ambient temperature.

Charging standards

USB-C Power Delivery: what it is, when you need it

USB-C Power Delivery (PD) is a standard that lets a device and a charger negotiate higher voltage and current, safely, up to 100 watts or more. It is what allows a power bank to fast-charge a phone or top up a laptop. The negotiation happens through the USB-C cable: the bank offers a set of voltages, the device picks the one it can use, and power flows at that rate.

If you only charge phones at standard speed, you do not need PD. Any USB-A or USB-C port at 5V will do the job. If you want fast charging, you need PD and a bank that outputs at least 18 to 20 watts. If you want laptop support, you need PD at 45 watts or higher and a bank large enough to meaningfully extend a laptop session.

Quick reference

5V / 5-10W (USB-A or basic USB-C): Standard phone charging. Slow but universal. Every power bank does this.

9V / 18-20W (USB-C PD): Fast phone charging. Fills a phone roughly twice as fast. Most mid-range banks support this.

20V / 45-65W (USB-C PD): Laptop charging. Requires a larger bank (typically 20,000 mAh or more) and a PD-rated USB-C cable.

20V / 100W+ (USB-C PD 3.1 or EPR): High-draw laptop charging. Few power banks support this, and the bank drains very quickly at this rate.

One important detail: the cable matters. A USB-A to USB-C cable cannot carry PD power, even if the bank supports it. For PD charging, you need a USB-C to USB-C cable rated for the wattage you are trying to deliver. This is the single most common reason a "fast charging" bank seems to charge slowly.

Types compared

Three formats, three jobs

Power banks sort into three practical categories based on what they are sized to do. Each has a clear use case, and buying the wrong format is the most common mistake.

Standard USB power banks (5,000 to 20,000 mAh)

The workhorse. A 10,000 mAh bank fits a coat pocket and charges a phone about twice. A 20,000 mAh bank is bag-sized and covers a weekend away from an outlet. Most offer USB-A output at 5V; better models add USB-C PD for fast charging. This is what most households need first.

Cost range: $15 to $50 for reputable brands. The price difference between a good 20,000 mAh bank and a mediocre one is usually about $10, and the good one uses better cells, charges faster, and lasts longer.

High-capacity power banks (20,000 to 30,000+ mAh)

Built for multi-day use or laptop charging. These banks typically offer USB-C PD at 45 to 65 watts, enough to meaningfully extend a laptop session. They are heavier (often 400 to 600 grams), and the largest models cross the 100 Wh airline limit.

Cost range: $40 to $100. Worth it if you regularly charge a laptop away from power or if you need multi-day phone capacity for a household of two or more during an outage.

Solar-integrated power banks

A standard bank with a small solar panel built into one face. The panel generates a trickle of current in direct sunlight. The appeal is real but the math is sobering: a typical built-in panel produces 1 to 3 watts, which means 20 to 50 hours of full sun to recharge a 20,000 mAh bank. In practice, a sunny weekend might recover a quarter of the capacity.

Cost range: $25 to $60. The solar panel is a bonus, not a primary charging method. If solar recharging is important to you, a separate folding panel (20 to 30 watts) paired with a standard bank is dramatically more effective.

Where power banks stop and power stations start

A power bank charges phones, tablets, and maybe a laptop via USB. If you need to run a CPAP machine, a small refrigerator, a fan, or anything with an AC plug, you are in portable power station territory. The overlap is small: power stations start where power banks end, and they cost and weigh accordingly.

What goes wrong

What fails and how to avoid it

Capacity that is not what it claims

Off-brand banks sold through marketplace listings sometimes carry inflated mAh numbers. A bank claiming 50,000 mAh at a price that reputable brands charge for 10,000 mAh is lying about its cells. Buy from established brands (Anker, Nitecore, Goal Zero, Baseus, Zendure, RAVPower) or check for independent capacity testing.

Degradation from storage habits

Lithium cells age fastest when stored fully charged or fully empty, especially in heat. A bank left at 100% in a hot car for months will have noticeably less capacity when you need it. The ideal standby state is 40 to 80 percent charge in a room-temperature drawer. Top it off when a storm is in the forecast.

Slow charging from the wrong cable or adapter

A bank that supports 18W fast charging will charge at 5W through a USB-A cable, or through a low-wattage wall adapter. The bank is only as fast as the weakest link in the chain. Match the cable and wall adapter to the bank's input spec.

Thermal runaway in damaged or defective banks

Lithium-ion batteries can overheat and catch fire if the cells are damaged, defective, or the protection circuit fails. The CPSC has issued multiple power bank recalls, including a 2026 reannouncement covering 429,200 units after reports of overheating, fires, and one fatality.¹ The risk is low with reputable brands, but a bank that has been dropped hard, is visibly swollen, feels unusually hot during charging, or smells of chemicals should be retired immediately. Never charge a power bank unattended on a flammable surface or under a pillow.

Air travel

Flying with a power bank: the rules that matter

The FAA regulates lithium batteries on aircraft because of the thermal runaway risk described above.² The core rules have been stable for years, but individual airlines tightened their own policies in 2026.³

FAA lithium battery rules for passengers

Under 100 Wh: Allowed in carry-on. No airline approval needed. No quantity limit under federal rules (but check your airline).

101 to 160 Wh: Allowed in carry-on with airline approval. Maximum two per person.

Over 160 Wh: Prohibited on passenger aircraft.

Checked baggage: Power banks are never allowed in checked luggage. If your carry-on is gate-checked, remove the bank and carry it with you into the cabin.

2026 airline-specific changes: As of May 2026, American Airlines and Delta limit passengers to two portable chargers at or under 100 Wh each. Southwest limits passengers to one. Several carriers now prohibit storing power banks in overhead bins and prohibit charging from them during the flight.³ Check your specific carrier before you travel.

The practical ceiling for an airline-legal power bank is about 26,800 mAh at 3.7V, which works out to 99.16 Wh. You will see this number on many banks marketed as "maximum travel capacity." If the watt-hour rating is not printed on the bank itself, calculate it from the mAh and voltage rating on the label: mAh times volts, divided by 1,000.

Making the choice

What to look for, and what to ignore

Look for

A watt-hour (Wh) rating printed on the bank. This is required for air travel and is the only honest capacity number.

USB-C input and output if you want fast charging. USB-C PD at 18 to 20 watts is the current sweet spot for phones.

A brand with a track record and a warranty. Anker, Nitecore, Baseus, Zendure, and Goal Zero are established names in this space.

Passthrough charging, which lets you charge the bank and your device at the same time. Useful when outlets are scarce and you want to top off everything overnight.

Ignore

Inflated mAh claims from brands you have never heard of, especially at prices that seem too good. Capacity fraud is common in marketplace listings.

Built-in cables. They break first, and when they do the bank is useless until you carry a separate cable anyway.

Wireless charging on a power bank. It is convenient for a desk, but it wastes 30 to 50 percent of the bank's stored energy as heat compared to a wired connection. In a preparedness context, efficiency matters.

The recommendations

What we recommend

New World Survival earns a small commission on qualifying Amazon purchases at no cost to you. This helps us cover operating costs and keep building new content. We only recommend gear we would put in our own kit. Commission never decides a recommendation.

Comparisons of specific products within each type are coming. When they publish, they will appear below and in the commerce strip above.

After you buy

Owning it well

A power bank is simple gear, but a few habits keep it ready when you need it.

Power Banks Guide

Everything about choosing, sizing, charging, traveling with, and maintaining a USB power bank.

Battery Systems Guide

How power banks fit into a layered household energy strategy alongside rechargeables and power stations.

Rechargeable Batteries

NiMH and lithium cells for devices that take standard sizes. The companion to your power bank.

Solar Basics

How to recharge a power bank off-grid with a folding solar panel.

Comparisons

All battery bank comparisons

Type-by-type comparisons publish as they are built. Each one earns its place through real research.

Sources

References

U.S. Consumer Product Safety Commission. "Casely Reannounces Recall of Wireless Portable Power Banks." cpsc.gov, April 2026.
Federal Aviation Administration. "PackSafe: Lithium Batteries." faa.gov, updated August 2026.
Federal Aviation Administration. "Airline Passengers and Batteries." faa.gov, updated August 2026.

The Weekly Readiness Brief covers gear, guides, and practical next steps every Tuesday.