How much electricity does the average computer use and how is this compared to a television?

that really depends on what type of TV you have and type of computer. like a Mac mini uses less energy that a regular PC tower. and flat screen LCD or LED use less energy than older TVs.

Average tower home-use-pcs have power supply units with 350 to 500 Watts. Depending on what parts you use. A gaming PC with good graphics will need more power than a box for your grandma where she reads cooking-recipes from the Internet. Older PCs used less power-input. Office PCs sometimes get as low as 200 Watts if build for power-saving.

Of course you also need an extra power-plug for the monitor. That should be added to power-usage when you sit in front of your computer.

The average Laptop will use about 75 to 80 Watts when charging.

For LCD-TVs I found devices with 80 to 200 Watts for 32” screen diameters and 174 to 380 Watts for 42” screen diameters. Depending on construction-series and manufacturer.)