Lately, with a lot of plug-ins on the roads, the HOV lanes are seldom helpful now as they have the same car density as all the other lanes, rush hour or not. Only very few sections the HOV lanes have an advantage. Oftentimes, it is slower in the HOV lanes now than in the regular lanes.
So I haven't installed the green stickers on my Siren Red Volt as it would make it look ugly.
Interesting difference between NorCal and SoCal:
"High-Occupancy Vehicle (HOV) lane, also known as the carpool or diamond lane, is a traffic management strategy to promote and encourage ridesharing; thereby alleviating congestion and maximizing the people-carrying capacity of California highways.
•HOV lane is usually located on the inside (left) lane and is identified by signs along the freeway and white diamond symbols painted on the pavement.
•In Northern California, HOV lanes are only operational on Monday thru Friday during posted peak congestion hours, for example: between 6 a.m. - 10 a.m. and 3 p.m. - 7 p.m. All other vehicles may use the lanes during off-peak hours. This is referred to as "part-time" operation.
•In Southern California, HOV lanes are generally separated from other lanes by a buffer zone. The HOV lanes are in effect 24-hours a day, 7-days a week, referred to as "full-time" operation.
The operational practices vary differently between Northern California versus Southern California because of traffic volumes and commuter patterns in the two regions. Northern California highways usually experience two weekday congestion periods during peak morning and afternoon commute hours followed by a long period of non-congestion. Using a full-time operation would leave the HOV lane relatively unoccupied during off-peak hours and would not constitute an efficient utilization of the roadway. Southern California experiences very long hours of congestion, typically between six to eleven hours per day, with short off-peak traffic hours; part-time operation under these conditions would not be viable."
https://www.quora.com/What-are-the-California-carpool-lane-rules