I have a Splendide washer/dryer on board (Italian made). It DOES require a pure sine wave power source. With a psuedo-sine wave inverter the power-on light MIGHT SOMETIMES come on, but it does not run. The manufacturer has confirmed the need for pure power.
I have to say I was sceptical, but it has been a GREAT addition. Uses a total of 13 gallons of water
for a wash and rinse, and when away from dock
power we line dry everything, and power use is actually quite low.
We did not upgrade the inverter, but rather use the washer only when running the generator
to charge the batteries. A very workable solution--for us.