for those that don't know
PSW is a realitive NEW technology
and really isn't PURE sine wave, its just functionally close enough for most things , as to be indistinguishable
but ..put it on an Oscilloscope and you can see the "pulse steps" in the wave form
before shrinking miniaturized digital technology allowed for this type wave form control
the top quality inverters were MSW, handled by stable electronic input through heavy transformers and output resonate filter chokes
this is OLD school tech
Tripp-lite was a pioneer in this many years ago
and today they build both types PSW and MSW with top quality
its the transformers and chokes inside the tripp-lite that make it heavy, durable, and clean output
the 1250w model weighs 23 Pounds
compare that to the avg 1000w PSW of about 8 pounds or less