The electricity consumption of a computer depends largely on the model and style. A large gaming PC will consume more energy than a small Chromebook or laptop. Determining the watts used by a computer is important for off-grid energy planning and for general knowledge of energy use as it pertains to your power bill and environmental impact.
The energy consumption of computer will vary, with common ranges in the 15-300 watt per hour range. Before assuming or making predictions, simply check the label for energy consumption. The manufacturers display this information on the back of the computer. They default to the maximum energy usage so you can safely assume the computer will consume less than listed on a normal day.
Modern laptop computers are efficient and use far less energy than older systems with large operating systems and heavy hardware. A typical laptop computer runs around 15-60 watts of consumption, and you can assume a similar usage for tablets as well. Using the computer while connected to WiFi increases the energy usage towards the maximum range. Offline use is the most efficient.
Desktop computers require more energy and they run anywhere between 70-250 watts. That energy use only applies to the tower and not the monitor, which will use an additional 20-60 watts. The energy range is wide on desktop computers because a large number of models exist. Assume a gaming desktop with a large monitor and heavy duty hardware system uses the maximum amount of energy while a smaller, bare bones desktop primarily using word processing software will use the lower end.
Planning Off-Grid Systems
The energy used is especially important for off-grid systems. For example, a house or camper running off battery systems will require a calculated approach to ensure the batteries have sufficient energy to power the computer. The watts used by computers, electronics and appliances will determine the battery sizes required and the number of batteries will in-turn determine the solar and generator requirements to charge the batteries.
Off-grid computer users must plan diligently and shut down their systems when not in use. A computer in sleep mode will continue consuming energy at a very low rate, but a shutdown computer will not consume anything. Ideally, you will charge the computer and run off battery with sleep mode or shutdown intervals between uses. This will reduce the energy consumption while preserving batteries.
Energy Savings Measures
The cost to run a computer depends largely on the hours used and current energy prices. The formula to determine cost is the watts multiplied by hours used, then divide by 1000 to get a result in kilowatt-hours. Next, determine the price per kilowatt-hour as indicated in your power bill and multiply by the kilowatt-hour number to determine the costs. You can break this out by day, month or by year.
After determining the costs, you can take measures to save energy while reducing the power payments. A gaming desktop can easily cost 500 dollars or more to run each year, and reducing the power consumption can cut that bill down significantly. Treat the computer much like you would an off-grid system to save a significant amount of money. The same applies to all electronics and even appliances.
Unplug and shutdown the system when it will not see use for several hours or longer. This is especially important when taking trips or leaving the system idle for several days as the sleep mode continues power consumption. Reduce unnecessary usage and limit time on the computer and other electronics to potentially save hundreds and even thousands in power bill payments.