If you have an APU, do you need an inverter

I don't think the APU can provide power for a microwave. as the APU only provides 12 volts and about 20A which is about 250W max.
You can not power a microwave from a 12V socket because it requires 120V and 1000W of power, not including the additional wattage for power up.

 

APU provides 12 volt DC, an inverter converts 12v to 120 volts AC (like your house). So if all of your appliances are 12v, you're good. But I bet the egg maker and laptop charger are 120v. If they use the household plug they're 120v. Hopefully that helps.

 

There are smaller inverters that plug into the 12V socket and provide enough power for a laptop, maybe even an egg maker.
No way for a microwave with those, sadly to say. They are limited to the power output of 12V and 20A. Getting close to that means some real heat and melting of the 12V sockets.

 

Unless their apu is a Carrier apu. Carrier apu's have a 5500 watt generator and an alternator. The generator side runs the HVAC compressor like a house heat pump and usually has 1 or 2 120v outlets wired in the truck for the driver to utilize household items. The alternator keeps the batteries charged so you can use the interior lights or 12v plugs (and if desired, can power an inverter). My last company had Carriers and had a 1500 watt inverter. I could use my air fryer off the generator plugs and my microwave on the inverter plugs. Made meal prep a lot faster.

 

If you are going to buy an inverter, I would make sure it has a feature called "pure sine wave". Pure Sine Wave PSW power is what comes out of your home electrical plugs. It's what most devices expect you to use. Some devices don't care if they get PSW or not. Devices that have wallwarts or transformers will overheat if they don't get PSW. The price difference between PSW and not are less than $50, if they even sell inverters that don't come with PSW. It may be so common now they stopped calling it a feature. I burned up 1 laptop power brick because of this. The charger on my electric razor was very hot.

 

For nearly a decade I powered my laptop with a 12V plug in inverter which was not a pure sine wave device.
No problems for me.
I have read about others with a different experience, but my laptops have always been gaming computers that require a bit more power. HP, Asus, MSI, and none of them failed to run properly with a modified sine wave inverter.

Pure sine wave has a signal that goes up and down like a rolling wave because it is analog, and the modified sine wave has a digital signal of one's and zero's so it is a square up and down pattern.

 

It comes with 2 foot cables to connect to the batteries. 2 feet? Really?
Connect to battery, drill straight up and push it through to the inverter exactly above.
And the other battery terminal is another foot away plus the curves in the line.