The full form of KTLO is keep the lights on
“KTLO” means “keep the lights on.”

Here, the “lights” in this internet slang term refer to the lights in a home or a business. Another way to say “KTLO” is “KLO,” or “keep lights on.”

In business, especially IT, “keeping the lights on” means doing enough to pay the electricity bill. That is to say that a certain part of the business that is dubbed as “KTLO” is something that generally performs well and is a quite stable source of income for the firm.

Example 1:
Co-worker 1: Another day, another dollar. How are things going for you? Having a good one?
Co-worker 2: Yeah, things are bad, but they aren’t that good either. I wish I could do more.
Co-worker 1: Not satisfied with your regular work? Are things getting dull?
Co-worker 2: Pretty much. I know Steve and Regina are out working on all the cutting edge stuff. They keep me on KTLO projects.
Co-worker 1: Hang in their man, the KTLO projects are what keep us from being homeless!