(Answer-
NEVER!) -
It’s awful tempting to purchase a modified sine wave (MSW) inverter when you look at the price
comparison (3 to 1 typically) to a true (pure) sine wave inverter (TSW).
You might recall the sine wave looks
like from your physics class in high school, well that is not what
you get with the MSW inverter output that you purchased because of
that tempting low-price. What you will get with the MSW is this
course” square looking” wave that is nothing more than abusive to
anything is it hooked up to other than a light bulb.
MSW inverters are great for running
motors and resistive loads (like incandescent light bulbs). Beyond
that you are probably asking for problems. Don’t even consider
running things such as plasma TVs, fluorescent lights, power tool
battery chargers, dimmable lights or anything that is clock / time
related. More than likely the equipment will not work, or if it does
it may run hot and burn out. Sometimes equipment connected to a MSW
inverter will make an audible noise or in other cases it makes them
create electrical noise affecting other pieces of equipment (such as
your VHF or SSB radio).
TSW inverters are needed on most
electronic equipment for proper operation such as: microwave ovens;
TV’s; Computers; cell phone chargers; LED lights and the other
huge gamut of products that have some electronics in them (which is
mostly what we plug into that 120 V AC wall outlet).
More often than not people that
purchase a MSW wind up finding out that their bargain purchase turns
out to be an unusable piece of equipment because most of what they
want to power will not work.
MSW inverters will make you equipment
scream “Stop it… your killing me”.
Save yourself the grief and just commit
to a True (Pure) sine wave inverter. Your electronics will work and
your equipment will be happy.