This info is not mine.
It was copied from Crutchfield's a recognized US retailer of Car Audio.
Tip 1: The general rule for upgrading the audio in a hybrid
Whether your hybrid is a Prius, a Fusion, or a Civic, hybrid vehicles have sophisticated electrical systems. And there’s a limit to how much you can tax the system with additional electronics.
As a general rule for hybrids, we recommend not exceeding a 30-ampere current draw on your battery, or a total output of 350 watts RMS from your audio system. Luckily, that still leaves you with lots of room for a great sound system upgrade in your ride. Since you're going to pass all those gas stations, you might as well enjoy your drive more.
An explanation of current draw
If you’re new to car audio, don’t let the technical terms intimidate you. To understand current draw, it helps to think about a water tank, which represents your car’s battery. Voltage is the amount of available power, represented by the amount of water in the tank. Electrical current is like water flowing through a pipe — the speed at which it flows is the current draw.
Wattage is the amount of work the current can produce — represented by how forcefully the water comes out of the pipe. When you pull too much current from the battery to produce more wattage, there isn’t enough voltage left to power other vital electronics in your hybrid.
Replacing the factory radio usually gives you an immediate bump in audio power and cleaner sound due to improved digital-to-analog converters. And the typical new car stereo isn't going to strain your electrical system. New speakers are an easy upgrade that doesn't negatively affect electrical current draw at all.
For our new stereo, we chose a Kenwood DVD receiver with a touchscreen display (find our touchscreen receivers here) to run the show. It offers Apple CarPlay™ and Android Auto™, which the factory radio did not include. Drivers would now have a lot more music options and stereo functionality on their company trips.
I had listened to some demo music on the factory system before the installation. It was a painful listening session. I can't believe we waited this long to upgrade this sound system. Once the Kenwood car stereo was installed, we did another sound check with the factory speakers still intact. The difference was immediate and impactful. The soundstage, which had been suppressed and lowered by the factory system, was now much more open and natural. We couldn't wait to continue.
For speakers, we decided on the Polk DB572 5"x7" speakers for the front and rear doors. These are hugely popular with our customers, as the reviews can attest. They also work well with a variety of music, and their efficiency complements the Kenwood stereo's power. In addition to the speakers, we also decided to go with a combination of Dynamat and a set of Stinger Roadkill FAST Rings to seal the speakers in the factory openings. These items also deadened unwanted noise and rattles, so we could get the best sound possible without interruptions. Anthony had experience with both, and he was very complimentary of the FAST Rings he'd used in previous vehicles. They're easy to install and can be cut to needed shapes.
Tip 3: Add the biggest amplifier you can
People always ask us, "Can I install an amplifier in my hybrid vehicle?" The answer is, Yes, you can! Since we're all music lovers here at Crutchfield, we understand the need for impact in your music.
When selecting an amplifier to install in your hybrid vehicle, check the total fuse rating of the ones you’re interested in. If the rating doesn’t exceed 30 amperes, you’re good to go. Your best option is usually a compact amplifier, because it’ll draw little current, is cost-effective, and stays out of the way.
Yes, you can even install a subwoofer in your hybrid
If you're using stereo power for your speakers, then you can add a subwoofer to the mix and further enhance the sound. When matching an amplifier to a subwoofer, subs that are efficient (with a sensitivity rating of 90 dB or higher) and have a power handling of approximately 200 watts RMS or less work nicely in keeping current draw down. Again, make sure your amplifier's fuse rating doesn't exceed 30 amperes.
Powered subwoofers are also a great all-in-one option to add more bass without creating problems for your system. For the car, we chose the a 10" powered subwoofer. It draws only 10 amperes of current, but still delivers some solid thump. It also features a detachable plug, so the enclosure can be removed if more cargo space is needed. Super handy!
Tip 4: Dial in your sound with in-depth tone controls
Many factory systems are equalized for the original gear installed in a particular vehicle. It’s often not optimal for everyone’s ear, nor is it very adjustable. But don’t worry! We offer several digital signal processors (DSPs) to get around the factory equalization and clean up that sound, even if you’re sticking with the factory radio. While we relied on the Kenwood stereo's robust sound-shaping controls for the vehicle, these outboard DSPs can also offer up additional features to factory radios, like built-in amplifiers or preamp outputs for additional amps.