AC/DC Inverter size vs. Efficiency

[JCDriller]

I'm currently building my camping trailer and I've purchased a Xantrex 2000w pure SW inverter to power the 110v electrical system. I've always used smaller inverters for other projects and that got me to wondering.

Do larger inverters utilize more 12v electricity to operate? Does an inverters efficiency go down as it operates closer to its maximum wattage?

Am I wasting my 12v battery's stored energy if I'm using a 2000w inverter to only charge my laptop computer vs. a smaller 300w inverter.

I assume watts in is watts out and there isn't any difference. Hopefully the larger inverter is built better and therefore will therefore be more efficient and lose less energy to heat.

Thoughts?

 

[Joe917]

Use the smallest inverter possible for the load. Larger inverters are less efficient on small loads and will use more on standby.
The most efficient way to charger the laptop is a dc-dc power cord, no inverter.

 

[DaveInDenver]

An inverter has an efficiency curve. Why they do is technical (happy to explain why), but suffice to say they can vary wildly.

This is a theoretical example of what two might look like. The red one is very good and the blue would be poor at light loads.



Some are designed to run well over a broad range of loading, for example grid tied inverters will handle light loads well because they may well run all over the place. Others want to be heavily loaded. That is more typical of cheaper ones. Some will be most efficient in the middle but fall off on each end, etc. A good manufacturer will provide this data if you ask.

Joe917's recommendation is a good rule of thumb. Very few are going to be highly efficient at 10% load as in your example. But without knowing yours specifically it's hard to say for sure. True sine wave inverters and high frequency inverters are usually better about this.

 

[Nd4SpdSe]

This is awesome info, thank you!