- Speed: Most models will boil a litre of water in around 3 minutes. But you may have a differential of up to 1 minute, depending on the model.
- Minimum capacity: You’ll save on power costs and get a faster result if you only boil as much water as you need. The ideal jug will boil as little as 1 cup (250mL), but the minimum capacity indicators on some models is 1 litre.
- Pouring: Water should pour smoothly to the end, but with all the jugs we tested it was hard to pour out the last cup. Models with a wide spout are a bit tricky to pour into a narrow opening.
Safety: Jugs are usually well balanced for pouring, but some people will have a problem with the weight. The sides and lids of stainless steel models get very hot and could burn children (or absent-minded adults).
Lightweight plastic jugs stay cooler to the touch and are easy to lift and use, especially if they are quite short and fit easily under the tap for filling. But they are more at risk of being knocked over than heavier, wide-bottomed jugs.
- Filling: Either the spout should be large enough for easy non-spill filling, or the lid should be easy to open. You also shouldn’t have to tilt the jug to fill it through the spout.
- Central connector: Also known as "all direction base." Many cordless jugs now have a circular base with the electric connector in the centre. This means they can be turned on the base and easily used by left and right handers. We think this is a great step forward. Whether you choose this or the older style with the connector at one side, make sure the jug fits securely and easily onto the base.
- Water-level gauges: Many jugs now have gauges on both sides, to suit left and right handers. With some, you can see right through the plastic. Both solutions are great. Some jugs don’t have an exterior gauge, which is a distinct disadvantage.
- Power on light: A valuable convenience and safety feature. Surprisingly, some models still don’t have this.
- Switches: They should be easy to use and to locate without having to look at them.
Cord storage: The unit should have some way of storing unwanted cord, so it doesn’t curl around loose, or worse, hang over the edge of the bench so a toddler can pull the boiling jug over. Storage is usually in the base.
Some models provide a choice of exit points, so you can stand the base in the direction that suits you best. This is valuable for any model that doesn’t have a central connection.
Safety lock lid: Some models have a locking device to keep the lid on if the jug is overturned, and stops that gush of boiling water.
Spout cover: This is a handy feature which helps limit spills. It’s also good if you have trouble with insects in your kitchen.
Scale filter: Valuable if your water supply is "hard" (or high in calcium carbonate), but that’s uncommon in New Zealand. Note that it won’t filter the water.
Cleaning: There should be a smooth surface with few crevices, to avoid accumulation of dirt. Plastic jugs are easier to wipe clean, but when grease and dirt gets ingrained it’s harder to shift than on stainless steel.
Comfort: When choosing a kettle, try the handles and pouring action of several models. Buy what feels most comfortable.
Auto-boil-off and boil-dry protection are common to all the models we tested.