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Car inverters

What Size Car Inverter Do I Need? A Simple Guide

By EchoRepel Team·13 September 2026·4 min read

Quick answer

Add up the running wattage of every device you'll use at once, then add headroom (around 20-30%) for safety and startup surge. For phones, laptops, cameras and small electronics, that lands around 200W — making a 200W pure sine wave inverter the right size. Appliances with motors or heat need far larger units.

Inverter sizing sounds like an engineering problem. It is really just a bit of addition. Get this one calculation right and you will never buy the wrong inverter. Here is the whole method.

Step 1: List what you'll run at once

Only count devices you will use at the same time. A laptop plus a phone charger is two items; a laptop you use, then unplug before charging a camera, is one at a time.

Step 2: Add up the wattage

Every device shows its wattage (or volts × amps) on a label or charger. Rough guide:

  • Phone charger — 5-20W
  • Laptop — 45-90W
  • Camera / drone charger — 25-60W
  • Wi-Fi router — 10-20W
  • Small fan or LED light — 5-25W

Step 3: Add headroom

Add roughly 20-30% on top of your total for safety and any brief startup surge. If your devices total 150W, aim for an inverter rated around 190-200W or more.

Where 200W lands

For the electronics most people actually carry — a laptop, phone, camera, maybe a small light — the maths almost always lands around 200W. That is why a 200W inverter is the sweet spot for car use. What it will not do is run appliances with heating elements or big motors (kettles, hairdryers, fridges) — those need far larger units and a heavier power source. (See can you run a fridge on a car inverter.)

And always choose pure sine wave for clean power that is safe for sensitive electronics. The EchoRepel 200W Pure Sine Wave Inverter is sized exactly for this job — enough for your gear, small enough to live in the glovebox.

Frequently asked questions

How do I calculate what size inverter I need?

Add up the wattage printed on each device you'll run at the same time, then add about 20-30% headroom. That total is the minimum continuous rating your inverter should have.

Is a 200W inverter enough?

For phones, laptops (45-90W), cameras, routers, small fans and LED lights, yes. It is not enough for fridges, kettles, hairdryers or anything with a heating element or big motor.

What is startup surge and why does it matter?

Some devices, especially those with motors or compressors, briefly draw far more power when switching on than when running. Leaving headroom stops that surge from overloading the inverter.

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