Prius 2006 Hazy Headlights

You need to seal the lens after cleaning with a UV protectant.
There are many
Here is one

 

2K spray clearcoat from autobody supply, maybe Eastwood also.

2K clear for auto paint seems to be more durable.

2K 2in1 Headlight Clear - SprayMax

Or

Solaray™ UV Clearcoat | clearcoat | SEM Products

 

Mine are not too bad and for the time being I am just waxing them. That holds up for a few months, then they get dirty and I wash them off with a bit of detergent to strip the wax and reapply. Advantage: cheap and not too time consuming. Disadvantage: not a permanent fix. On previous vehicles I have been down the road with sanding, coating, etc., etc. and none of those fixes hold up for more than a couple of years in SoCal - too much heat, dust, and UV. When my current ones get beyond the point where waxing is good enough I think I will just replace them with a pair of TYC's from RockAuto, which are only $140 (plus tax and shipping) for the pair.

 

Maybe with hazy headlights all bets are off, but anyway, IIRC with any car we've ever had, there's a caution to not use wax on headlights. This is from page 343 of 2nd gen Owner's Manual:



I'll resist getting into my rant about how things have not improved, since the demise of sealed-beam glass headlights. Ah woops...

 

Instead of wax, just apply the Blue Magic spray once every three months. Takes five minutes. One bottle lasts years.

 

2k clearcoat apply once. lasts years. For the same price. Every vehicle has 2k clearcoat protecting paint. Should be OK for poly carbonate.

 

yep, that will work too
Advance Auto Parts - Down for Maintenance
$6 or less

 

In my experience that stuff attracts dirt even worse than the wax does. It is very dusty and dry in SoCal, lots of little particles in the air. If a surface is even slightly tacky (which the Blue Magic is) that builds up a thin coat of, well, mud, very quickly. Perhaps that isn't a problem elsewhere.

I believe the warning against waxing the headlights is because they are afraid some grit will get mixed in and then when the wax is polished it will scratch the headlight plastic. Perhaps that might actually be a problem on new and pristine plastic, but on old hazy plastic it seems like a minor worry.

 

It appears we’ve given the OP at least three things to try. Hopefully he’ll report back on one or more of them.