Does using an external display via HDMI drain laptop battery faster?

[DNMehta]

Hello , 

I own an Envy 4 1104TX and normally, it gives me a battery back up of around 5 hours with W8 64-bit.

However, today I connected it to an external monitor (Dell) while watching a movie and it gave me a battery back up of just about 2 hours.

At first, I thought it may be my antivirus which might be causing it, but I checked the last acitivities in my BitDefender and it didn't do anything  during the time I was watching the movie. utorrent was continuously on and downloading a couple things via wifi but that is about it. The bluetooth was disabled and there were no other external devices conected at the time. Windows updates or scan(s) were not running either.

I just want to know if this is normal or if I should be worried.

Thank you   

[Huffer]

The electricity to send video signals to the big display has to come from somewhere. I am a bit surprised by the size of the difference but the battery will clearly last for a shorter time pushing signals to two instead of one display.

[DNMehta]

I'm sorry, I need to clarity this, the laptop lid was closed. It was just the external display that was running.

[Huffer]

Then something is odd because the backlight on the external is powered from wall power. Pushing to an external monitor only ought to make the battery last longer, not shorter. But if you are, say, watching a DVD on the external monitor you are going to run down the power quickly to turn the motor on the DVD drive. In other words, make sure your 5 vs. 2 hour comparison is fair. Are you doing exactly the same things?

[Udara]

As I understand downloading torrents at a considerable download rate can keep your hard drive busier and it won't let the drive to be powered off as it does when you are doing some continuos reading and also it makes the network card to run at higher power mode. The other thing huffer explained if you were watching a dvd the drive motor can drain some considerable amount of power. From my experience if I starts playing my audio cds windows remaining time drops out to somewhere 2.30hrs, if not it will show something like 5.30hrs. One more thing quality of the movie can draine some power when compared to a low quality one as it needs more cpu power process it.