A Tesla Model S police cruiser sounds like a good idea on paper.

Swift acceleration and almost no engine noise means it would be easy to sneak up on suspects or speeders, and the Model S’s range is good enough to quell almost any anxiety about running out of juice.

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Well, the Los Angeles Police Department tested a couple Model S P85Ds loaned by Tesla for almost a year, and the LAPD isn’t quite sold. There are two hesitations: The cost of the vehicles, and what would happen to the electric grid in the face of a large-scale power outage.

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On the other hand, one of the reasons the LAPD tested the Model S in the first place was to gauge the Tesla’s ability to handle itself in high-speed pursuits.

“Is it practical now? No,” LAPD Police Administrator Vartan Yegiyan told CNBC. He also said that over “the next three to five years … not only will the industry push toward electrification, but prices will drop on vehicles. More models will be coming out, and the electricity and electrical grid will become more robust, and more charging stations will be available. While that’s occurring we’ll be in the space learning and contributing to the process.”

The cost of a Model S P85D is about $100,000, while a typical police vehicle used by the LAPD would start around $30,000, with prices climbing to $45,000 or $50,000 when outfitted with the equipment police need.

The LAPD, which has 23 electric scooters and around six electric motorcycles as part of a broader city commitment to lease 160 pure EVs among various city departments, also has tested the BMW i3, which is less expensive than the Tesla.

As it is now, the LAPD buys 600 to 750 vehicles per year, paying up to $30 million, so the Models S may just cost too much at present.