How to Calculate What Size Inverter You Actually Need
Choosing the right inverter doesn’t have to be complicated. Once you know how your gear uses power, it is easy to find the right inverter size for your setup.
What an Inverter Actually Does
An inverter’s job is to take battery power (DC) and turn it into the same type of power you get at home (AC).
The bigger the appliances you want to run, the more power the inverter needs to supply.
Running Watts vs Startup Watts
Every appliance has two power numbers:
Running Watts
This is the amount of power it uses once it’s operating normally.
Startup / Surge Watts
This is the short burst of power needed to switch on — common in fridges, compressors, Air conditioners and other devices with motors.
Most inverter issues come from underestimating this surge.
For example, a 90W fridge might spike to 400W just to start.
If your inverter can’t handle the spike, it will shut off even though the running load is small.
Add Up What You Use at the Same Time
Think about what you’ll actually run together — not every appliance you own.
A simple touring setup might only include:
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a fridge,
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phone/laptop chargers,
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some LED lights.
A more serious camping or off-grid build may include:
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coffee machines,
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microwaves,
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induction cooktops,
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power tools.
- Air Conditioner
The more gear you stack together, the bigger your inverter needs to be.
Give Yourself Headroom
Inverters perform best when they’re not running at their absolute limit.
If your appliances use 700W, a 1000W inverter is a better choice. It will run cooler, work more efficiently, and last longer than a 700W inverter that is pushed to its limit.
A little oversizing is always worth it.
Typical Inverter Sizes by Use Case
Light Power Needs (phones, laptops, small fridge)
500–1000W is usually enough.
Medium Setups (coffee machines, microwaves, tools)
Expect 1500–3000W depending on the highest-wattage appliance.
Large Off-Grid Systems
Anything from 3000W+ for running big loads or multiple appliances at once.
Why Pure Sine Wave Matters
Most modern electronics, compressors and motors run best — and safest — on a pure sine wave inverter.
It delivers clean, stable power and avoids damaging sensitive equipment.
Modified sine wave inverters may cost less, but they can create noise and heat. They might also lower performance or cause some appliances to fail.
The Simple Rule
Your inverter needs to cover:
Your total running watts + your highest surge wattage + some extra headroom.
Get this right, and your setup will be more reliable, efficient, and stress-free. This is true whether you are camping, touring, or building a full off-grid system.
