APC Back-UPS Pro 900 BR900G-GR UPS 900 VA / 540 W, 230 V

A UPS rating is given in two ways. 900 VA is the apparent power, while 540 W is the real power that all connected devices may draw in total. When choosing what to plug in, go by the watts: if the computer, monitor and router together draw less than 540 W, the UPS can handle the load. Leaving some headroom also extends the battery runtime.

A short outage without a UPS means unsaved work and a computer that switches off abruptly. The Back-UPS Pro switches to battery power during an outage and gives you time to save files and shut the computer down normally. If the power comes back quickly, work carries on without interruption and the router keeps the internet connection up.

540 W is enough for a typical home or office workstation: a desktop PC, one or two monitors, a router and a network switch. A gaming PC with a powerful graphics card may draw more under load, so check the real consumption of your devices before connecting them. A laser printer is usually not connected to a UPS because of its high inrush current.

According to the manufacturer, the UPS weighs 10.85 kg. Most of that is the battery, so place the unit on the floor or a sturdy shelf where it stays out of the way and air can circulate around it. Plug the UPS straight into a wall socket rather than an extension lead, and leave enough room for the cables.

Home offices and small offices where a power cut must not mean lost work; users whose router and network gear need to ride out a short outage; small servers or NAS units that need time for a clean shutdown; and anyone whose area sees the power drop out now and then.