Here is an example of a compact conductor.
Is this actually an improved product or still the same turd with a different colored bow?
Were not in the 60's any longer, and neither is the aluminum alloy used for conductors. Many of the bad experiences were from internal house wiring, and installations where the equipment terminations were not designed to allow for aluminum conductors. There was a problem with thermal expansion and corrosion in the early products. It still has a greater coefficient of expansion, under load than copper, but not near as bad as it used to be.
Earlier products needed to be wire brushed to remove oxides immediately before termination, and then coated with anti oxidant compound to prevent future oxidation. This is no longer required, but is still a good practice, especially where terminated outdoors.
Most distribution equipment lugs today are made of the same material and are approved for either type metal. With termination lugs of the same material, the temperature expansion is less of an issue as they expand at a similar rate.
This conductor is used for services and large feeders almost exclusively today, especially on large and long runs, to reduce cost. However it needs to be up sized from an equivalent copper conductor, which means that the conduit needs to up sized as well.
It isn't even offered in individual conductors in small sizes generally, as would be used in branch circuits for equipment and general loads. The exception is in home cables such as for a range, A/C or dryer circuits.
The most cost savings can be had with underground use, with PVC conduit, as compared to rigid steel conduit and copper conductors. If the circuits are oversized, from the bare minimum requirements, that reduces most of the expansion from running under loaded conditions.
Even many distribution transformers are wound with aluminum wire today, and terminated in aluminum lugs.
The long term reliability of aluminum is really dependent on the selection of material, insulation type and installer skill. It can be used effectively to reduce cost, dependent on conditions. It is widely used, and stable when done properly.
Copper is still the premium material. Conducts away heat better. Less corrosion effects, and the corrosion is still conductive. Best used for heavy demanding loads and all internal building small feeders and branch circuits. But comes at a premium price.
Any competent electrical contractor should have no problem pricing a job with either material, where it is appropriate for use.
SAF Ω