Does installing two amps and subs decrease mpg?

in short, yes.

1 horsepower = 745ish Watts. so you can see that adding an 800 watt draw to the power system will cause the engine to run a little more and eat up a little more gas.

The speakers and sub i wouldn't worry about, as they are provided power from the amps (either the ones you are installing or the factory amp or factory speaker, depending on model number) and thus are already factored into the equation.

The real question is, will it be noticable? IMHO, not really. variances in MPG from your driving habits and conditions will most likely overshadow any effect this has. although if you have tracked several years of MPG prior to and after the install, you might notice a slight decline (at most like 1 MPG i'd say) in the overall average MPG.

 

400 Watts will not be a problem for the Prius in terms of MPG and power consumption. I think it is more likely that the weight of the stereo equipment would affect the MPG more. There's about 50 pounds of equipment in the back of my Prius. I compensate for that mass by being a lightweight

 

The "absolute" answer is "yes" - but the "real" answer is "no, not really".

Driving into a 10 mph headwind will eat more gas and decrease your mileage more than running your amp.

 

If you mean 400 watts of audio power, remember that amplifiers are not terribly efficient. Many will require much more than 400 watts of input power to produce that output.

Check the power draw and see. But still you're only sucking up one or two horsepower, which isn't much.

If you aim the subs out the rear of the car, perhaps you can get some propulsion from them

 

You might want to also be warry of something. Im not sure how true it is as well.

I've thought about upgrade the 12v "aux" batt to handle a higher load which would be a little better on the car.

more Amp Hour batt and good current discharge from it means better sound...

but i have learned that if you draw i think 120 amps or more you could blow a fuse for the DC\DC charger. this charges the aux batt, and if that happends, your car will stop, and won't be drivable until you replace the fuse.

i asked some question, and from what i can see, a 600 or 700 watt system is probably the best and safest bet.

...im still toying around with the idea a little.

also 120 amps @ 12v DC would mean 1440 watts of power.

now, with no headlights or AC, there is a 200w load on the car.

if your AC is 200 and your lights are 200...

...you should stay around 800 or less...

there are other ways to get more current avaible, HID lights, LEDs for cabin... still looking to shorten some electric demands.

 

Make sure you take into consideration the crest factor of the sound. Except for a few test signals, no recorded sounds are constantly at max level. A 1000W amplifier will only put out that 1000W for the loudest passages, and most of the time it will be putting out 100W or less. So the mileage impact is quite low unless you're listening at full volume all the time.

 

Someone mentioned a reasonable compromise here in another thread...

Upgrade all 4 speakers, and install a 4-channel amp.
Run the rear speakers off the stock HU (it's fill after all)
Run front components off 2 of the 4 channels, and bridge the other 2 to power a sub.

 

You know, every little thing you do to a car, adds weight to it, and thus, decreases the mileage. SO, unless you drive naked, on a empty stomach, expect less mileage.

At some point, you have to enjoy the car, for that is part of the joy of owning a car. And so what if you drop a mile or two? You are still getting much better mileage then most cars on the road, and you are, in fact, helping the planet.

 

I currently running about 900 watts of audio, is that bad for my electrical system,?

 

Using standard industry practices (SIP)..Nope.

frodoz Stereo Upgrade | PriusChat

 

The real answer is also 'yes'. Any power draw uses energy. That is what those two words mean. (It should be noted that 400 watt amplifiers don't draw 400 watts continuously.) The world is made up of things which individually have a very small effect, the total is always the sum of all those small things. Ignoring them just because they are small would mean that you ignore the entire world.

 

Nope. All carbon dioxide (for example) is exactly equal. None of it helps the planet (as things stand at the moment). It ALL hurts the planet. There is no baseline level that you are allowed, and being below that is helping. The atmosphere can't tell the difference between Carbon from a Hummer and Carbon from a Prius.

 

Dup.