I have a super low-wattage one, its 600w. That means it boils water quite slowly BUT.... even on a cloudy day, my solar panels create enough free electricity to run it. So free cups of tea! I also fill a mug with water, pour that into the kettle and boil it - not one unnecessary drop of water is heated. I'm very pleased with my setup. (If I had a 3000w standard kettle I'd get my drink 5 times faster but would need to pay to import the power unless it was a really sunny day).