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# Energy consumption of my laptop

Discussion in 'Hardware' started by fxpip, Jan 16, 2008.

1. ### fxpip

Does windows has a feature that allows me to see how much Watt my computer is consuming ?

2. ### rcanfiel

there is usually a power/battery consumption installed on most laptops

3. ### fxpip

Yes, there is but it doesn't tell me how much Watt is being consumed at each moment , just how much time there is left at the present power consumption rate..

Any idea how much Watt is being consumed at the lowest CPU power settings and the lowest LCD brightness settings on a 17 inch Acer with intel core duo processor ?

4. ### fxpip

Doesn't windows has a built-in Watt teller ?

5. ### late apex

Here's how to estimate your laptop's power consumption at any given moment.

Step 1. Look up the power ratings of your laptop battery, in Volts (V) and Milliamperes (mAh). You'll usually find them printed on the battery itself, as well as published as part of the specs -- for the laptop (if using OEM battery) or aftermarket batteries.

Example: 14.8 V and 6,450 mAh

Step 2. Convert the above to watt-hours power rating:

Volts x Amperes = watt-hours

Example: 14.8 V x 6.45 Ah = 95.46 Wh

So, this particular Li-Ion battery can supply 95.46 W for 1 hour... or 47.73 W for 2 hours... etc.

Step 3. Have your laptop unplugged, running only on battery power, in a specific hardware / software / energy state you want to test.

Step 4a. IF the power gauge shows remaining time, divide that time, expressed in hours, by the power rating in watt-hours.

Example: 2h30m remaining

95.46 Wh / 2.5h &asymp 38 W

This is your instantaneous power consumption.

Step 4b. IF the power gauge shows remaining % of full capacity, then:

- note the exact time it takes the gauge to decrease by 1%

- divide the power rating in watt-hours by 100 times that time, converted to hours.

Example: 90 seconds to go from 67% to 66%

100 x 90 / 3,600 = 2.5 hours

95.46 Wh / 2.5h &asymp 38 W

This is your instantaneous power consumption.

6. ### late apex

It should be added that, before Step 4a (but not 4b), the battery needs to be fully charged.

For both 4a and 4b, the closer the battery is to its original spec, the more accurate your power consumption estimate will be. If the battery's output capacity has been degraded, say, after hundreds of discharge / recharge cycles, you'll obviously get an overestimate.

Another, far more general and flexible, option would be to use a dedicated device like this.

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