TL;DR, Get 1500 watts minimum electric kettle in North America. Lower than that is useless, might as well use your microwave.
There is a reason that electric kettles are common as dirt in the UK and not in North America. Power. Well, actually voltage. Most of the kettles in the North American market are under powered because of the 120V standard. A higher wattage for the US (1500 watts or more) kettle comes close to eating up a 15 amp kitchen circuit all by itself. It’s worth it to commit that circuit1, especially if you have a newer (30 years) kitchen with multiple kitchen counter circuits required by code.
Lower power kettles (under 1500) take way too long to bring the water to boil. Other methods become faster, if not easier.
I have a 15 year old Krups model that is 1750 watts at 120v2. This is the highest power rating I’ve seen on a standard kettle available in the US. That’s on the hairy edge of acceptable for an American circuit, but I gladly commit that circuit to the kettle alone. I love the time and temperature it buys me. For any volume, it is 50% faster than my microwave and even more than that vs the stovetop.
The UK uses 240 volts as a standard. Therefore, they can have much higher power kettles. Due to their voltage, the UK has 3000 watt kettles for ~$40. That 3000 watt kettle uses twice the voltage and the same number of amperes as US voltage 1500 watt kettles. It is the number of amperes that matters to your circuit protection system, whether fuse or circuit breaker.
A 3000 watt kettle can boil water at an amazing rate. It’s almost as if it were on demand, especially for smaller amounts of water.
So that’s why every UK household has an electric kettle and loves it and Americans can’t figure out why you would ever want one. Voltage and Amperage. By the way, the same exact thing is going on with certain other countertop appliances, such as waffle irons.
For more information on how the UK is different than the US in regards to power, here is a very interesting video on the UK power plug. It is arguably the best in the world.
1 – “Commiting a circuit” here refers to while the kettle is in operation only. I use it enough during the course of a day that I can’t use anything else of any importance on that circuit if I want the kettle available at all times without thinking about electrical load. YMMV due to how you use your kettle and other devices that may be on that circuit at other times.
2 – I like this thing so much that after it went off the market years ago, I purchased a spare on ebay to use when the first one dies. That was 7 years ago. I still haven’t had to use the spare one. The current kettle has been used for over 10,000 cycles or thereabouts, estimating 2 cycles (or cups of tea) a day for 15 years.