Four years into its second generation, it's midcycle refresh time for compact Q5 SUV. That means tweaked front and rear fascia designs with new head- and taillights, updated tech and, most interestingly, a larger focus on the newest member of the family: the 2021 Audi Q5 55 TFSI E Quattro -- which I'll just be calling the Q5 plug-in hybrid for brevity. The Q5 PHEV slots between the base Q5 45 TFSI and the high-performance , offering a flexible balance of power, economy and refinement.Like the base Q5, the PHEV is powered by a 248-horsepower, 2.0-liter, turbocharged four-cylinder engine. It rides on the same multilink independent suspension as the standard model, though its components are retuned slightly to compensate for the extra weight of the hybrid system. Aside from the presence of two filler doors -- one for gasoline on the passenger side and one for the electric charging port on the driver's -- the PHEV is virtually indistinguishable from its more conventional counterparts. The plug-in hybrid's gasoline engine is mated with a 141-hp electric motor that boosts total output to 362 hp, just edging out the SQ5's 349-hp V6 and making the PHEV the most powerful Q5 variant in the lineup. However, its 4,619-pound curb weight -- about 331 pounds more than the SQ5 -- means that it's less nimble than the S model, and therefore slower to 60 mph. The PHEV does the deed in 5.0 seconds, versus 4.7 ticks in the SQ5. The PHEV's 2,000-pound towing capacity is also lower than the 4,400 pounds the other Q5 models can pull.A seven-speed dual-clutch transmission sends the PHEV's 369 pound-feet of torque through the Q5's Quattro With Ultra all-wheel-drive system -- Audi-speak for front-biased AWD with on-demand rear axle engagement. This setup balances traction when you need it but returns improved fuel economy when you don't. And for snowy or dirt-road conditions, the Quattro system has selectable off-road programming that engages the rear axle more liberally. Connecting the Q5 PHEV to a Level 2 (240-volt) charger juices its 14.1-kilowatt-hour battery pack in about 2.5 hours. Plugging into a regular ol' 110-volt outlet stretches out to an overnight charge. With a full battery, the Q5 boasts 19 miles of electric range.Unlike many plug-in crossovers in this class, the Q5 PHEV's battery doesn't cut into the cargo area -- all 25.85 cubic feet behind the rear seats are intact. The gas tank had to shrink, however, in order to make room for the hybrid components, so it now holds 14.3 gallons versus 18.5 in the other Q5s.The Q5 PHEV makes up for its smaller tank with a significant improvement in fuel economy relative to its siblings. Taking into account the electric range on the front end, Audi estimates 43 miles per gallon equivalent in the city, 64 MPGe on the highway and 50 MPGe combined. That's more than double the 25 combined mpg for the base model and 20 combined mpg for the SQ5.Hitting the road in EV mode with a full battery, I'm able to hit exactly 20 miles of electric range thanks to a light foot and smooth driving style, even with a couple of steep hills on my route. In its EV mode, the PHEV is extremely quiet, with just a slight hum from the powertrain that becomes a touch more prominent during regenerative deceleration. There's plenty of power in EV mode for running errands, and the electric acceleration is strong and smooth off the line. Two thumbs up.Like any good hybrid, the combustion engine doesn't stay on once it wakes up; it shuts down during coasting and idling to conserve fuel, which is great. Rolling onto the throttle, the electric motor handles the first few feet of acceleration while the gas engine fires up, and then the two motors seamlessly work together while the Q5 is humming along. As long as your inputs are relatively smooth, you won't even notice. Stomping the gas pedal in Hybrid mode gives you the full surge of electric torque during acceleration, followed by a momentary dip in power while the gasoline engine catches up. Repeating this experiment in Sport mode, the gasoline engine stays on most of the time and there's no transition during electric motor handoff -- the SUV simply launches without the weird chug.So, just leave it in Sport all the time, right? Well, no. This transition hiccup is only noticeable during mat-the-pedal, full-throttle acceleration. The other 99% of the time, the hybrid SUV is perfectly smooth and confident in its acceleration. So drive like a normal person -- or activate Sport mode before your stoplight drag race -- and you'll likely avoid this problem. Plus, Sport mode somewhat cancels the Q5 PHEV's biggest advantage over its siblings: fuel economy.On paper, the 50-MPGe Audi looks less efficient than the 60-MPGe BMW X3 xDrive30e and the 68-MPGe Mercedes GLC350e. In reality, the 2020 model-year Q5 PHEV with the exact same powertrain boasted an EPA-estimated 65 MPGe -- pretty close to that of the GLC -- and Audi tells me that it simply adjusted how it estimates fuel economy for the refreshed 2021. Audi says the new numbers should be more realistic, which is good, since I've always found PHEV SUV numbers to be a little optimistic anyway.As is often the case with PHEVs, your mileage will vary depending on how often you charge and how far you drive. On shorter trips with a full battery, for example, I can see over 100 MPGe. On longer trips that deplete the battery, however, I only average around 30.1 MPGe. All told, I ended up with an average of about 41.3 MPGe after a few days of testing, which included lots of time in Sport mode on hilly roads. You could end up anywhere in that range, but I imagine that most Q5 PHEV buyers who charge daily and commute around 15-30 miles per day will end up more or less in line with Audi's 50-MPGe estimate. Cabin and safety tech revisions The MMI Touch dashboard infotainment gets a new, 10.1-inch center screen and now features specific menus for monitoring and adjusting the PHEV's recharge schedule. Overall, the updated cabin tech is faster and more responsive than before, with a new generation of silicon powering Audi's smartly designed interface. Drivers can use Audi's onboard navigation software or connect their phone via a USB for Android Auto or wirelessly for Apple CarPlay.The Q5 is also available with Audi's 12.3-inch Virtual Cockpit Plus full-digital instrument cluster, which puts onboard navigation, audio source information and advanced trip computer monitoring near the driver's line of sight and at their fingertips. A full-color head-up display is also available.On the safety side, Audi Pre Sense City collision mitigation is standard equipment for all Q5 models, as are rear cross traffic detection with auto-braking, lane departure warning, auto high beams and parking distance sensors. My example included optional adaptive cruise control with traffic jam assist, lane-keeping steering assist with hands-on wheel detection and top-view camera system that helps with safe and precise parking. Pricing and competitionThe 362-hp Q5 PHEV is more powerful than the 288-hp BMW X3 PHEV and the 315-hp Mercedes GLC PHEV, but it does come at a slight efficiency cost. Other plug-in alternatives hitting the road next year include Lincoln's Corsair Grand Touring and a whole bunch of premium fully electric crossovers for drivers ready to fully embrace EV driving, like Audi's own E-Tron. The 2021 Audi Q5 45 TFSI starts at $44,395 (including a $1,095 destination charge) for the base Premium model. The Q5 55 plug-in hybrid climbs to $52,995 at the same trim level, an $8,600 price hike. Audi estimates that the PHEV qualifies for up to $6,712 in federal tax incentives, which should soften the blow somewhat. Plus, depending on your charging and driving habits, there's tremendous potential for savings at the pump that could make the PHEV even cheaper over time than the base model.My top-trim Navarra Blue metallic Prestige tester packs all the upgraded cabin tech, driver-assistance goodies, a Bang & Olufsen premium audio system and more, and rings up at $63,190 before incentives. That's about $3,000 more than a comparably equipped X3 PHEV, but on par with the cost of the plug-in GLC350e.The core Q5 has always been a solid choice in the compact luxury space, and the 2021 model-year upgrades make it more compelling. Electrification and hybridization only make the Q5 PHEV feel more luxurious, quieting down the powertrain and adding an effortless smoothness to the experience.