It wasnt a tech school question. It was a design question.
You could have said: "I don't know"
I also could have said, "Your question, as you phrased it, makes no sense, and
that should be obvious to anyone who has a few weeks of trade school under
their belt. So, I'm going to assume you don't. Here's how to calculate what
you need."
If you would really like an answer to your question and aren't just trolling,
here are some observations...
Derating power resistors for loading to 50% of rated wattage is a standard
practice, although I'd personally think that's on the conservative side. A lot
of it depends on how conservative you want to be, what type of voltage waveform
you're applying to the load, and duty cycle considerations. You haven't seen
fit to give us any of that information, though, so I would suppose 50% power is
a good place to start.
As of when I'm reading this, no respondent to your original question can make
sense of what you're asking or figure out what you need. Possibly you might
want to take a deep breath, then drop the assumption that the respondents to
sci.electronics.design can read minds (I already get that from The War
Department, thank you), and work on the hypothesis that you could phrase your
question a little better.