Wireless charging has a long way to go before it replaces wired charging, but the technology has advanced dramatically in the past few years. Everyone with the newest smartphones, wearables, and other gadgets can get behind the idea—simply place your device on a charging pad or stand and let it sit. Within a few minutes, you’ll have more battery power than you did before, and you didn’t have to fuss with wires or cables to get it.

But quite a bit of technology goes into make an accessory that makes your life that much easier. Most wireless chargers come in the form of circular or rectangular pads, some of which are propped up on legs to make stands that take up minimal space and work well as nightstand or desk accessories. But don’t be fooled by their minimalist exteriors—there are a number of things you should know before investing in a wireless charging pad. To navigate this murky world, Ars tested out some of the most popular devices available now to see which are worth buying.