The general perception is that the less hours a course is worth the less is the value of the certificate. It’s got to be said though that employers rarely specify how many hrs a TESL/TEFL Certificate should be worth. What matters to them is that you are certified.
Generally 100hrs is the maximum amount of hours a totally online course can offer and it is also a well regarded standard. You’ll find that 100+hrs usually apply to in-house courses, or hybrid online/onsite courses.
Personally I would recommend that more than the number of hrs attached to a certificate anyone thinking of registering in a TEFL course should look at the course content; how the course syllabus compares to others; if the course allow for personal tutor’s guidance; what credentials the tutors have, etc.
You should make sure the course requires some actual work on your part and it is not based on “Yes or No” answers or “Read This Unit and Summarize It” type of coursework.
It is also a good idea to find out what other students who have taken the course say about it. Independent sites like
TEFL Course Review for example can be very useful as they allow for TESL/TEFL courses and course providers to be independently reviewed and rated by those who have acyully taken each course.