How Many Watts Does a Home Office Use?

Laptop, monitor, router and modem wattage, plus simple runtime math to keep your home office working through a power outage.

A home office is one of the easiest things to back up. The loads are small, the gear is low power, and a modest battery can keep you working for hours. This guide shows what each piece uses and how to work out your own runtime.

What each device draws

Look at the power adapter or label on every device. You will usually see volts and amps, or watts, printed in small type.

• Laptop: Many laptops draw a modest amount while working and more while charging or doing heavy tasks. The adapter rating is the maximum, not the typical use.
• External monitor: Typically a small to moderate load, and bigger screens draw more.
• Router and modem: Both are small, steady loads, but they run all day.
• Desk lamp: LED lamps are tiny loads.
• Phone charger: Very small.
• Desktop computer: Considerably higher than a laptop, especially with a graphics card.
• Printer: Draws little when idle but spikes while printing.

Do the runtime math

Add up the watts of everything that will be running at the same time. Multiply by the number of hours you want to work. That gives you watt-hours. Then compare with the battery capacity. Because of conversion losses, you will get less than the printed capacity, so leave a margin. The full method is in how to calculate watt hours.

1. List each device and its watts.
2. Add them up to get total watts.
3. Multiply by work hours to get watt-hours.
4. Add a safety margin and compare with usable battery capacity.

A worked example with made-up round numbers: if your laptop, monitor and router together draw 100 watts, then a four hour work session needs about 400 watt-hours before losses. A battery with comfortably more than that would cover it.

Don't forget the internet

Your computer is useless without a connection. Your modem and router need power too, and if your internet service goes down with the grid, you may not be able to work anyway. Cable and fibre connections often depend on powered equipment in the neighbourhood, and cell towers have limited backup. See how to keep Wi-Fi and internet on in a power outage and how long a power station runs a TV and Wi-Fi router.

A phone hotspot is a good backup. Keep your phone charged, and check your plan for hotspot limits.

Battery backup options

A small UPS gives you a few minutes to save work and shut down. A power station can carry you for hours. Which one fits depends on how you work. Our guide UPS vs power station for a home office compares the two, and working from home during a power outage covers the practical side. A power bank can also keep a laptop going if it supports the right output.

Save power while working

• Lower screen brightness.
• Turn off the external monitor and use the laptop screen only.
• Close heavy apps and video calls when you can use audio only.
• Turn on battery saver mode.
• Unplug the printer and other extras.
• Charge the laptop fully before the weather turns bad.

Think about comfort and ergonomics

Outages often come with dim rooms and cold or hot weather. Set up your workspace near a window for daylight, and use a small LED desk lamp rather than overhead lighting. In winter, wear layers and a hat so you are not tempted to run a heater from your battery, which would drain it quickly. See space heaters and electric blankets for why that does not work well.

Make a short outage plan

Decide in advance what you will do if the power goes off in the middle of the day. Save work often, let your employer know your options, and keep a charged battery within reach. If you work from home often, add a small station to your kit. See the power station hub for sizing guidance.

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