A battery’s kWh rating is its total energy capacity, and it can range from under 0.1 kWh in small devices to 100 kWh or more in electric cars.
There’s no single answer to how many kWh in a battery because the number scales from tiny device cells to full electric-car packs. A typical smartphone battery stores about 0.015 kWh, while a large EV pack can hold 100 kWh or more. kWh tells you how much total energy a battery can store, so it’s the clearest way to size anything from a phone to a home backup system.
What Does kWh Mean For A Battery?
A battery’s kWh rating is its energy storage capacity, not its power output. One kWh means the battery can deliver 1 kW continuously for one hour, so a 1 kWh battery can also run a 500 W device for two hours. kW is the rate of flow at any instant, while kWh is the total amount stored.
You can see the relationship with a simple example. A 60 kWh battery can supply 60 kW for one hour, or 30 kW for two hours, before it’s drained. That works because energy equals power multiplied by time.
Use the same math in reverse. Divide the battery’s kWh by the device’s kW draw to estimate runtime: a 10 kWh battery running a 500 W load gives about 20 hours in ideal math, before real-world usable-capacity limits lower it.
The same unit applies across everything. Phone, laptop, home storage, and EV batteries all state capacity in kWh or in watt-hours, which is simply one-thousandth of a kWh. Two mistakes cause most confusion:
- Treating kWh and kW as the same thing. kWh is the tank size; kW is the flow rate.
- Reading a kWh rating as “kW per hour.” A 60 kWh battery does not produce 60 kW every hour; it stores 60 kWh total.
How Many kWh Do Battery Packs Actually Hold?
Battery sizes vary widely, but the practical range runs from about 0.015 kWh in a phone to well over 100 kWh in a long-range EV. The table below groups the capacities you’ll actually see.
| Device Or Use Case | Typical Capacity | Notes And Examples |
|---|---|---|
| Smartphone | About 0.015 kWh | A 15 Wh phone battery equals 0.015 kWh |
| Laptop | 0.05–0.1 kWh | 50–100 Wh packs are common |
| Portable power station | 0.5–2 kWh | Small units run lights and phones |
| Home storage battery | 5–15 kWh | 12 kWh is a popular middle-ground size |
| 2011 Nissan Leaf | 24 kWh | Early mass-market EV pack |
| Hyundai IONIQ 5 | 58–77.4 kWh | Varies by trim |
| 2025 Kia EV9 | 76.1–99.8 kWh | Varies by trim |
| 2025 Volvo EX90 | 111 kWh gross / 107 kWh usable | Reserved capacity helps protect battery life |
| Tesla Model S | 100 kWh | Common long-range pack size |
EV Database’s usable-capacity cheat sheet lists real usable numbers for dozens of EVs, and those figures often sit below the advertised battery nameplate. For home backup, 12 kWh is a common floor; if that’s the size you’re weighing, our picks for the best 12 kWh battery round up the models worth comparing.
Gross vs. Usable: Why The Rating Isn’t The Whole Story
The number printed on a battery is often gross capacity, but the amount you can actually draw is usually lower. Manufacturers reserve part of the pack to protect battery life, so usable capacity is what matters for real-world range and runtime. The 2025 Volvo EX90 is a clear example: 111 kWh gross, about 107 kWh usable.
The same logic applies to most EVs and home storage systems. When someone quotes a battery size, check three things: gross or usable, the power draw in kW, and the exact model year or trim, because capacity can change between versions.
FAQs
What’s The Difference Between kWh And kW?
kWh measures stored energy, while kW measures the rate at which that energy is used. A 10 kWh battery can run a 1 kW appliance for roughly 10 hours, or a 2 kW appliance for about 5 hours. Think of kWh as the size of the tank and kW as the speed of the faucet.
Why Is Usable Capacity Lower Than Advertised Capacity?
Manufacturers reserve part of a battery pack so cells spend less time near full charge and empty, which slows degradation. The 2025 Volvo EX90 has 111 kWh gross capacity but about 107 kWh usable. The reserved buffer is why usable capacity can be lower than the headline number.
Do All EV Batteries Have The Same Capacity?
No. EV packs vary by model, trim, and model year. The 2011 Nissan Leaf had a 24 kWh pack, modern Hyundai IONIQ 5 trims range from 58 kWh to 77.4 kWh, and the 2025 Kia EV9 ranges from 76.1 kWh to 99.8 kWh. Check the exact year and trim before comparing.
References & Sources
- EV Database. “Usable Battery Capacity of Electric Cars.” Shows usable capacity figures for dozens of EV models, which often fall below gross ratings.