Assuming your using a USB port to power your device, the answer is 2.5 Watts. A maximum of 500mA at 5V can be drawn from a Usb port. Power = Current * Voltage, which is 2.5 Watts by 0.5 Amps giving you a power output of 2.5 Watts
http://en.wikipedia.org/wiki/USB#Power
http://en.wikipedia.org/wiki/Power_(physics)#Average_electrical_power_for_AC
The power rating of an electrical appliance represents the rate at which the appliance uses electrical energy. It is typically measured in watts and indicates how much electricity the appliance consumes when it is in use. Higher power ratings suggest that the appliance uses more energy.
as much as you can
1440 Watts
How much energy it uses
110 Volts (V)
70%
The average cost of laptop power adapters is about $80 to $100 USD. You can find more affordable power adapters, but the quality and life span will not be as good.
Most new appliances have a power rating label on them. The Energy Star label is an indication that the appliance is more energy efficient than others and will tell you how much the appliance will cost you to run. Appliances that do not have an Energy Star label are not a good investment.
With a laptop, much of the chip & motherboard design is bespoke (to fit it into the space and power constrains of a laptop) and does no lend it self to upgrades.
The amount of power required to run an electric appliance depends on how many kilowatts of power it uses. The cost to run the appliance depends on how much your company charges per kilowatt. <<>> The amount of power depends on how much power it was designed to take. Some appliances are designed to take as little as possible, like radios, TVs and computers. Others are designed to turn electric power into another form of power, like mechanical power (motors) or heat power (space heating). These tend to use more power. The amount of energy paid for via the bill depends on the sum of the energy used by all the appliances. For each appliance it's the power drawn multiplied by the time it was used.
Unlike the CRT monitor, LCD doesn't use as much power. So, the battery of the laptop is enough to power its LCD monitor. There is a power supply cables within the laptops. That cables carry the power from the battery to its LCD monitor and other power needed devices. It is the simplest answer of how is the LCD on the laptop powered?
It actually does a little bit, but not as much as being turned on.