I have a customer who purchased an LCD tv and wants to mount it over his fireplace mantle. He'll keep his existing cable box and DVD player in the original location. I need to run power and an HDMI line to the new location. What kind of separation do I nedd between the two so I don't have an interference issue?
Study Guides for VDV / Structured Cabling Installers
I let this lay here for a couple of days because I know I will be flamed but I don't think you will ever see any interference between 60hz power and a shielded HDMI cable, even if you tywrapped them together. If you are really worried a few inches of separation will be plenty. Bear in mind a "twisted pair" for 60hz would only need a couple twists a mile to be overkill. The wavelength is over 3000 miles long. (look at a power line) The normal twist in romex as it comes out of the box is way more than enough. Just don't be a neat freak and untwist it when you staple it.
You won't have an interference problem so don't even worry about it. HDMI is a digital interface and that makes it even more immune.
What I would worry about is changing the HDMI cable or adding something else later (there are several inputs you know). I would run smurf tube from the back of the monitor to where it comes out by the cable box. Make it large enough to get component cables with their RCA plugs through as well a a couple of HDMIs.