Buy an inverter that's too small and it shuts off; too big and you've overpaid and added bulk. The trick is simple: work out the watts you actually need. Here's how, with a quick reference for common devices and why 200W is the sweet spot for most people.
The one rule: add up the watts, add headroom
Every device lists its power draw in watts (W) on its charger or label. Add up everything you'll run at the same time, then add about 20–30% headroom so the inverter isn't running flat out. Pick an inverter rated at or above that total.
Quick reference: typical device draw
| Device | Typical draw |
|---|---|
| Laptop charger | 45–100W |
| Phone / tablet charger | 10–30W |
| Camera / drone battery charger | 10–40W |
| Portable monitor | 10–25W |
| Router / modem | 10–20W |
| Small car fridge | 40–70W |
| CPAP machine (no humidifier) | 30–60W |
A laptop (say 65W) plus a phone (20W) is 85W — well under 200W. Even a laptop, a phone and a small fridge together usually stay within 200W.
Why 200W suits most people
For a mobile office or a road-trip charging setup, 200W gives real working headroom without being bulky or overloading a car socket. It is the practical middle ground: enough for laptops and electronics, small enough to run from a 12V socket sensibly.
What 200W will NOT run
High-heat appliances draw far more than 200W and need a much bigger inverter and a hard-wired supply:
- Electric kettle (1000W+)
- Induction cooktop (1200W+)
- Hair dryer (1000W+)
- Most power tools
Don't try to run these from a compact car inverter — size and socket limits make it impractical and unsafe.
Two more things to check
- Pure sine wave — for laptops and electronics, insist on it; modified sine wave can cause buzzing and charging issues.
- Your socket's limit — the cigarette-lighter socket often maxes out around 120–180W continuous; for more, wire to the battery with a proper fuse and keep the engine running.
The simple takeaway
Add up your devices, add headroom, and for laptops and everyday gear a 200W pure sine wave inverter like EchoRepel's covers the vast majority of real-world needs — clean power, sensible size, safe for your electronics.