Inverter Sizing Calculator: Don’t Starve Your Appliances
Inverter Sizing Calculator: Don’t Starve Your Appliances
Choosing an inverter is not just about matching the numbers on the box. A “2000W” inverter might fail to start a 1000W fridge. Why? Because of Surge Current.
Use this tool by ShockTrail to calculate both the Continuous Watts and the Surge Watts you actually need.
The Power Calculator
Select your appliances to see the recommended inverter size and type.
Inverter Sizing Tool
Power Logic by ShockTrail0 Watts
Pure Sine Wave
⚠️ Pro Tip: Buy a W unit to allow for future upgrades.
The “Silent Killer” of Electronics: Modified Sine Wave
There are two types of inverters. One is cheap, and one is safe. Knowing the difference will save your laptop and fridge from burning out.
| Inverter Type | Waveform Shape | Safe For… |
|---|---|---|
| Modified Sine Wave | Blocky / Steps | Old drills, simple heaters, incandescent lights. |
| Pure Sine Wave (PSW) | Smooth (Grid Quality) | Everything. Required for CPAP, Laptops, Fridges, Microwaves. |
According to Xantrex (a leading manufacturer), using a modified sine wave inverter on sensitive medical equipment like CPAP machines can cause motors to overheat or fail.
Understanding Surge (Peak) Power
Inductive loads (anything with a motor, like a blender, AC, or fridge) need a massive burst of energy to start spinning. A fridge might run at 100W, but it needs 800W for 2 seconds to start. This is called “Locked Rotor Amps.”
Read more about induction motor starting characteristics on Wikipedia’s Engineering Section.
Idle Consumption: The Hidden Drain
Big inverters use power even when doing nothing. A 3000W inverter might burn 50W just sitting there “on”. That is 1.2kWh per day—enough to drain a small battery! Always verify the “No Load Current Draw” in the spec sheet, as recommended by the Solar Reviews Expert Guide.
Frequently Asked Questions (FAQ)
Can I connect a 12V inverter to a 24V battery?
No! This will instantly destroy the inverter and possibly cause a fire. The input voltage must match exactly.
How thick should the cables be?
Inverters pull massive current. A 2000W inverter at 12V pulls nearly 170 Amps. You need very thick 2/0 AWG or 4/0 AWG welding cable. Check our Wire Size Calculator.
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