Battery and charging
What is a UPS and what does its VA rating mean?
A UPS (uninterruptible power supply) is a battery unit that sits between the outlet and your devices: if the power goes out, it keeps them running for a few minutes so you can save your work and shut down calmly, or keep your router online. Its capacity is listed in VA and in watts (W).
VA and watts are not the same
VA (volt-amperes) is apparent power; watts are the real power it can deliver. A 1,000 VA UPS usually supplies well under 1,000 W; the spec sheet should list both values.
To choose one, add up the watts of the devices you will connect and pick a UPS with headroom above that total.
Types of UPS
Standby (offline): switches to battery when the power cuts out. Line-interactive: also corrects voltage sags and surges without using the battery, which is very useful where the grid is unstable. Online (double conversion): always runs from the battery; it offers the most protection and costs the most.
A UPS is not a generator: its battery is meant for minutes, not hours. For long outages, use an inverter with batteries or a portable power station. There are also small DC mini UPS units to keep a router and internet running.
What to check before you buy
- Add up the watts of what you will connect and leave at least 20–30% headroom.
- If the voltage in your area dips and spikes often, choose a line-interactive UPS with AVR.
- To keep just the internet up, a mini UPS for the router is usually enough.
Guides to help you choose
Frequently asked questions
A typical computer UPS is not designed for a fridge compressor. For that, use a pure sine wave inverter with batteries or a power station with enough output.