What size generator

Look at the hardware store for a device called a "kill-a-watt".
They are available at most big box stores ~20 bucks.
Unplug the trailer, and using a 15-30 amp adapter plug the power cord into the device, and it into the wall. There are several displays available, the watt one is that you want. As said above, the startup draw can be 2-3 times running power, so but more generator then you think you need.
I haven't looked at generators in ages, but Yamaha has a line of inverter generators that could pull power off the starting battery to help cover surges, this may allow you to get a smaller generator then one that does not.

The reason I say to use the kill-a-watt is the converter is also pulling power, as well as any other 120 volt electronics. A generator that surges to 1.5 kw may not be enough if the converter is pulling 2 or 3 hundred watts, and has a poor power factor.

As others have noted, figure out the wattage for all the equipment you will be powering and try to find a generator that can run that load "CONTINUOUSLY".

Be careful when selecting a generator. Some are rated at their "Peak" wattage for like a minute, them drop back to a nominal wattage. Also note that some items have have a "Surge" when they initially power-up. Like an air conditioner for example. Many have a surge of something like 2.2 kw, but once they get going, they will run continuous at something like 1,000 watts or so. Some generators actually take this into account, like Yamaha's actually have a "Surge" rating where they can go above their continuous rating for a short time. Just read the fine print on a generator, know its continuous output, and check to see if it also has "Surge" capabilities as well.

The 1.5 is what you would use and add 25% to.

So about 1900 watts for the generator.

The popular Honda is only 1600 watts. It might work at sea level--but might well not work at greater altitudes either.

The Yamaha 2400 watt would more probably be a good fit.

my microwave says 1.5 kw power consumption and
1000 watts max output.

Which number should I use?

Keep in mind that the advertised cooking wattage of a microwave is much lower than what it actually takes to run the appliance. So a 900 watt micro can easily draw 1500 watts.

Hi

Add up the actual MEASURED wattage of the item you wish to run.

Purchase a generator that is 125% of that number.

Example:

1591 watts X 1.25 =~ 2114 watts of capacity for the genny.

Locate wattage of each device connected. this would be minimum wattage of genset.

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I have one of these very small dorm type white faced 600WATT manual operated Microwave unit $35 from WALMART that runs great using my 2000W EU2000i Honda generator or my 1500WATT PSW AIMS Power Inverter.

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It will NOT run on my 600WATTS AIMS PSW Power Inverter unless I make the setting to almost nothing and then start raising the setting after it starts up.

My goal was to have a microwave unit to use when camping OFF-ROAD that would run off my alternate power situations to make my 5-minute whole potato into a baked potato being wrapped in SARAN WRAP.

My fifth wheel trailer will not operate my 13,500 BTU Air Conditioner or the high wattage Microwave unit using my 2kw EU2000i Generator setup.

My POPUP trailer also will not operate my 13,500BTU Air Conditioner using my 2KW EU2000i generator. My popup trailer has the air conditioner equipped with a 120VAC 20AMP style plug that I have to plug into this special receptacle when setup when camping. I have adapted this directly to my 2kW Honda Generator receptacle with nothing else hooked up and it still would not start up my 13,500BTU Air conditioner. I did get to run one time by starting the fan first then kicking in the compressor and it ran that one time until it cycled the first time them tripped the breaker...

My personal tests here involved... We enjoy steaks on the grill with baked potatoes from the microwave camping off the power grid with my OFF-ROAD POPUP trailer. Hmmmm Good stuff...

Roy Ken

A watt is a watt is a watt. In an ideal world a 1000w microwave would require a 1000w generator. But in real life there are losses involved so it requires more. The 2k generator would be fine since some are 2k max and 1600 run.