Plug-in hybrid electric vehicles (PHEVs) are the darlings of auto shows, forward-thinking consumers, bloggers, and the gang at Google. Unfortunately, you can't stroll into Crazy Larry's PHEV Hut and drive one off the lot today. The quickest way to plug in is to order a Prius conversion kit from an after-market supplier.Here are three companies that sell kits to convert 2004 and newer model Prius hybrids into PHEVs. Note that each company uses a different battery technology:

1. Hymotion (A123 Systems)
Prius owners can order a hybrid-to-plug-in conversion kit from A123 Systems' Hymotion division. The company says its Nanophosphate™ lithium ion batteries supplement the factory-supplied battery pack and extend the capacity of the Prius to in excess of 100 MPG.

A123's Hymotion kit must be ordered online. The cost is $9995 and includes installation. Be prepared to wait. Delivery is "subject to customer demand and product availability." And once it's delivered, the kit will have to be installed by a certified Hymotion partner. It may be a long drive, however, because installers are only in 6 cities.

2. Plug-In Conversions
Like A123 Systems, Plug-In Conversions promises 100+ MPG, but it uses a NiMH (nickel metal hydride) battery pack from Nilar instead of lithium ion.

The cost is $9,750, $14,900, or $19,750 depending on the low-speed EV-only range of 8, 16, or 24 miles per charge. The company will install the batteries at its California facility. Here's a mileage chart. Orders may be placed online, but timeframe for delivery isn't available.

3. Plug-In Supply
At $4995, Plug-In Supply Inc.'s PbA (lead-acid) PHEV conversion kit is the lowest-priced of this bunch. The strategy is to allow customers to enter the PHEV at a lower price point, while giving them flexibility to upgrade to longer-range lithium iron phosphate batteries in the future, when the cost declines.

The company says a Prius using its conversion system has "an all-electric range of 10 to 15 miles and improved average mileage of up to 100 miles per gallon."

To order, see Plug-In Supply's 9-state network of dealers.

Is it worth the cost to convert a hybrid to an PHEV? That's part math problem and part personal values conundrum. The answer depends largely on how much you drive and a how badly you want to to be at the front of the fleet.