When I replaced a service a few months ago, I got enough Cu to make the run from the meter box to the panel, just in case.

When I opened everything up, the old entrance (60A) was Al, when they upgraded a few years ago, they re-used it, and ran Cu for the other leg. I stripped out the Al (It was too short for the new panel...darn ) and replaced it with new THHN/THWN Cu.

I don't completely trust Al...

Doug...
I expressly note & advise my customers that if they choose to keep their existing aluminum feeder conductors (if they're salvageable)when I do a subpanel changeout, their warranty goes from our company standard for this type of work (10 years) to miniumum allowed by CA contractors law (1 year)
50% of the subpanels I've had to changeout over the years have been from a loosened aluminum connection similar to the above if I hadn't found it for another few weeks or months.. The subpanel above was saveable with some time getting to know a wire brush & some Noalox... Usually I find them with a phase in full melt-down, insulators melted, lug frozen from the arcing & heat...
The other 50% are Zinsco.. need I say more?

-Randy

I know that al. conductors have poor qualities when it comes to copper. But, If Al. conductors keep loosening up and cause arcing over time, why doesn't the power companies have similiar problems? I have seen the lugs on the utility side and it looks like the day it was first landed, but take a look at the lugs after the meter and holy crap, blackened, loose and looking pretty bad.

Laguna...
They do! I've been on many service calls that ended up having a loose or corroded PoCo connection being the problem.. One of them was at night, Homeowner lost a phase from SoCal Edison... I looked up at the pole & the phase that'd dropped from his house was glowing from all the resistance at connectors for the neighboring houses... If you open up a typical PoCo residential pedestal, usually you'll find signs of something arcing at one time or another.. These are all Al. connections.. Another member on the board here that'd be alot better informed on the PoCo side of things would be Bjarney... I'm just speaking from my own experiance when dealing with the local PoCo's..

The only PoCo I've seen that Ive never had to call out for trouble service was SDG&E...(Not to say they "never" have problems...)But most of their system is copper!

-Randy