I have long maintained that if the gas/electric hybrid technology was going to be successful, automakers were going to have to package it under the hood of cars with proven mass-market appeal. It seems that Honda came to the same conclusion, adding it to its venerable Civic line in early 2002 and introducing it as an ’03 model.

The move seems to have paid off. Honda led all other automakers in consumer registrations of hybrid vehicles in calendar year 2003, according to registration data just released by R.L. Polk & Company. The Civic Hybrid alone accounted for half of all hybrid vehicles registrations in 2003.

According to the R.L. Polk data, national hybrid vehicle registrations rose 25.8 percent in 2003 versus 2002, while Honda Civic registrations doubled.

The main differences between the 2003 and 2004 Civic — hybrid and standard — are mainly cosmetic. But while the original Honda hybrid, the Insight, screams “Geekmobile” to most people, the Civic, a proven sales leader, uses the very same hybrid drive train, while adding the practicality of four doors and room for five.

Toyota has done the same basic thing by upsizing and restyling its third generation Prius into the mainstream,and adding its own hybrid system as an option to the Lexus RX series, while Ford is offering a hybrid system in some of its Escape SUVs as well.

Like the Insight, the hybrid Civic boasts two sources of power — a small gasoline engine and an even smaller electric one. The gas powerplant is a 1.3-liter SOHC eight-valve four-banger with variable valve timing. It’s rated at 85 horses and 87 pound-feet of torque — usually adequate power for getting around. But there’s also a wafer-thin 10-kilowatt electric motor that adds its 13 horsepower output to the total. Called Integrated Motor Assist (IMA), the system has the electric motor positioned between the gas engine and the transmission. During coasting and braking, the motor does double duty, acting as a generator to recharge the nickel-metal hydride batteries, which are stowed between the rear seat and the trunk.

It goes without saying that the whole objective of the hybrid drive arrangement is to boost fuel economy while reducing carbon monoxide emissions into the atmosphere. The hybrid Civic delivers on both counts. However, with a curb weight some 600-plus pounds heavier than the Insight, the fuel economy figures aren’t quite as dramatic. The hybrid Civic still delivers a more than respectable 47 city and 51 highway miles per gallon with the standard five-speed manual. With the optional continuously variable automatic transmission (CVT), it’s and 48 for both. Either way, it’s enough to propel the Civic near the top of the EPA’s miles-per-gallon chart.

As mentioned earlier, besides looking exactly like the mainstream Honda Civic sedan, the hybrid boasts a highly practical dimension missing from the geeky-looking two-seat Insight — it’s essentially the very same front-wheel drive, four-door compact sedan as its non-hybrid sibling. The Civic is roomy as well as fairly comfortable for its size, with easily understandable instrumentation — including monitoring the charging system — and ergonomically pleasing climate, audio, window and mirror controls.

It also offers reasonable handling thanks to independent front struts, coil springs and anti-roll bars front and rear, as well as a multi-link rear suspension.

Standard safety features include front disc and rear drum, vented ABS brakes, and driver and passenger air bags. Side curtain airbags are optional.

Whines: As high as I personally am on the hybrid technology — not just from Honda, but other manufacturers as well — there are still some caveats. Acceleration is leisurely at best when compared with that of the conventional gas-powered Civic, and it degrades in direct proportion to the state of battery charge and on how many passengers and/or how much weight is on board. With a full charge, a hybrid Civic with a manual transmission will do the 0-to-60 drill in just over 10 seconds. But with only a partial charge, it takes longer — more than two seconds longer.

My other concerns are battery life and battery replacement cost. These are two questions I’ve been unable to get a straight answer about from any manufacturer. However, they have said the individual cells in the batteries are replaceable, so the replacement cost can possibly either be minimized or spread out over time.

Bottom Line: Just like the regular Honda Civic, the hybrid Civic comes pretty well equipped at all trim levels — even for a compact, economy car. You basically just need to choose the colors, sound system options and which transmission you want.

I really like the hybrid technology and would like to see it evolve to the point it can easily power larger vehicles — like SUVs — and the choice of drive trains, gas or hybrid, become dollar-neutral. But right now, the premium manufacturers are charging for their hybrid technology concerns me. In Honda’s case, at just over $21,000 for a Civic hybrid with the CVT, it’s $2500 more than a top-of-the-line Civic EX. How many miles — even at today’s high gas prices — will it take to recoup that difference?

On the other hand, if you want a politically correct car, it doesn’t get any more correct than this — and to committed environmentalists, the difference is a small price to pay for the good they believe they’re doing and feeling they get from doing it.