When you shop for a portable power station, a solar battery, a power bank, or even a replacement battery for your device, two specifications always appear: Watts (W) and Watt-hours (Wh).
These two units may look similar, but they explain very different things:
Watts (W) tell you whether a battery can power your device.
Watt-hours (Wh) tell you how long the battery will last.
Once you understand this distinction, choosing the right battery becomes much easier.
1. What Are Watts (W)?
Watts represent power—the amount of energy a device needs at any moment to operate.
For example:
An induction cooker: 1500W
A hair dryer: 1200W
A laptop: 45–100W
A small fan: 30W
These values describe the “instant demand” of the device.
For a battery, this means:
A higher watt output allows it to run more powerful devices.
If the watt rating is too low, the battery may fail to start the device even if it has plenty of energy stored.
Watts (W) = Can the battery run the device?
2. What Are Watt-hours (Wh)?
Watt-hours represent energy capacity—how much total energy the battery can store and deliver.
Wh directly determines how long the battery can run a device.
Examples:
A 200Wh battery can run a 20W device for about 10 hours.
If you use the same battery for a 100W device, it may last only 2 hours.
So, a larger Wh value means longer runtime.
Watt-hours (Wh) = How long can the battery run?
3. The Real Difference Between W and Wh
You can think of the difference like this:
| Unit | What It Means | Practical Question |
|---|---|---|
| W (Watts) | Power output | Can the battery power the device? |
| Wh (Watt-hours) | Total stored energy | How long will it last? |
Simple analogy:
W is the engine horsepower.
Wh is the fuel tank size.
Both are important in different ways.
4. Why You Shouldn’t Look at Only One Number
❌ Mistake: Only checking Wh
A battery may have a large capacity, such as 500Wh, but if its max power output is only 100W, it cannot run a 300W appliance.
❌ Mistake: Only checking W
A battery may support 500W power output, but if it has only 80Wh of capacity, it will run out in less than an hour.
So, always check both:
W → device compatibility
Wh → runtime
Both determine whether the battery actually suits your needs.
5. What W and Wh Mean in Real Life
Portable Power Stations
W: Can it run your laptop, projector, fridge, or cooker?
Wh: How many hours can it power them?
Solar Energy Systems
W: Maximum output of the inverter
Wh: How much energy storage you have for daily use
E-Bikes and Electric Vehicles
W: Motor strength
Wh: How far you can travel on one charge
Backup Power (UPS)
W: How many devices it can support at once
Wh: How long the backup lasts
6. The Easiest Way to Read Any Battery Specification
Step 1: Know your device’s power requirement (W)
Check the label on your device.
Examples:
Mini fridge: 60W
TV: 100W
Router: 10W
Step 2: Make sure the battery’s watt rating is high enough
If the device needs 120W, your battery must output at least 120W.
Step 3: Decide how long you need the device to run
If you want a 60W fridge to run for 10 hours, you’ll need around 600Wh of energy.
Step 4: Choose a slightly larger capacity
Real-world use includes power loss, temperature effects, and battery aging.
So, if you need 600Wh, choosing 700–800Wh is more practical.
This simple method works for almost all battery applications.
7. Summary
Watts (W) show whether the battery can power your device.
Watt-hours (Wh) show how long the battery can run it.
You must check both W and Wh to choose the right battery.
Wh is the best way to compare battery capacity across different voltages and sizes.
The correct decision-making order is:
Confirm device wattage
Estimate runtime
Choose a battery with enough W and Wh
Understanding these two units will help you avoid common buying mistakes and choose the right battery for any application.
FAQ: Common Everyday Questions About W and Wh
Does higher Wh mean longer use?
Yes—Wh directly represents energy capacity.
However, runtime still depends on the device’s watt consumption.
A high-Wh battery will only last long if your device doesn’t use too much power.
Why can’t my battery run some devices?
Yes—Wh directly represents energy capacity.
However, runtime still depends on the device’s watt consumption.
A high-Wh battery will only last long if your device doesn’t use too much power.
Why does the battery drain fast?
Several everyday factors can shorten runtime:
Devices draw more power when starting
Cold temperatures reduce battery efficiency
Conversion losses in inverters
Running multiple devices at the same time
So real-world usage is often 10–20% shorter than theoretical calculations.
What should I check first when choosing a battery?
Always check:
W (Watts) — can the battery power your device?
Wh (Watt-hours) — how long do you need it to run?
If both numbers match your needs, you’ve chosen the right battery.
