I have a one KVA step down transformer that is 277v to 120 volt. How many watts of Christmas lights can I run on it?

Where are you using a 277V transformer?

where he works no doubt.

transformer basic principle is power in=power out

1000/277=3.6A draw

1000/120=8.3A load side.

do not exceed this, transformer needs overload protection.

Simple answer to the question is the 1 KVA transformer, no matter the voltage, can handle 1000 watts, without getting into the difference between kW and kVA.

If someone is dealing with 277 volts at a commercial or industrial facility, they should not be asking questions here, they should be properly trained and qualified to deal with this voltage.

If someone is intending on using a 277 volt transformer at home, we need to know this piece of information, hence the reason Stan is asking "where", and this person should be advised to stop until we know all the details.

If someone is dealing with 277 volts at a commercial or industrial facility, they should not be asking questions here, they should be properly trained and qualified to deal with this voltage.

If someone is intending on using a 277 volt transformer at home, we need to know this piece of information, hence the reason Stan is asking "where", and this person should be advised to stop until we know all the details.Thank you for posting this.
I had a post just like this all ready to go and let it slide. I didn't feel like dealing with the repercussions.
Thank you for posting this.