Why is there a current in my house panel grounding strip
Looking at your question and reading your background I am betting you may have a lot of electronics in your house and you actually have two problems. First you are picking current in a ground and second you seem to have an unusual power consumption. When you put them together as single problem it generally boils down to Harmonic Distortion, K-factor. Electronics, as an example a UPS, have a habit of recreating the wave and causing a distortion due to the time lap in the return current in the neutral. Also Electronics have a habit of using the ground as a handshake between components causing a current flow in a ground.


  K-factor is a weighting of the harmonic load currents according to their effects on transformer heating, as derived from ANSI/IEEE C57.110. A K-factor of 1.0 indicates a linear load (no harmonics). The higher the K-factor, the greater the harmonic heating effects.


I am not sure but by reading your question I think the water pipe your are clamping to is not bonded back to the single point of reference at your ground. If that's correct you really need to do that. Also instead of trying to troubleshoot the panel try and turn off any electronics in you residence and see if that helps correct your problem. 

As far as knowing whether or not this is the real problem with your power consumption. You would really have to run a power analysis to know for sure. FYI this type of equipment runs in the neighborhood of about $5,000.00. So I would suggest you find someone who does this for a living and try and work out some sort of quote if you feel it is necessary. 

Hope this helps.