So the reason you can’t just “add more amps” is US wiring standards. Most houses have 15 or 20A circuits. This puts an upper limit on the amount of wattage a single circuit can pull of either 120x15= 1800W or 120x20=2400W. This is going to be the biggest bottleneck, since going above this rating will either trip your breaker or light the cables on fire in your walls.
Beyond that, most plugs in homes are NEMA 5-15 outlets, which also limits the output of a single plug to 15A. If a manufacturer wanted to use a NEMA 5-20 plug to get that extra 5 amps, you’d need a different receptacle and thicker wiring to safely use it. Since most people don’t have 5-20 plugs, there isn’t really a reason for manufacturers to make them.
All of this is why pretty much every electric kettle made to work with the US electrical system is slower than ones made for 240V systems. Also, they all take about the same amount of time to heat a specific volume of water, so cheap ones are going to do just as good of a job as expensive ones.
All of these same limitations apply to space heaters as well, since they are essentially doing the same thing.
So the reason you can’t just “add more amps” is US wiring standards. Most houses have 15 or 20A circuits. This puts an upper limit on the amount of wattage a single circuit can pull of either 120x15= 1800W or 120x20=2400W. This is going to be the biggest bottleneck, since going above this rating will either trip your breaker or light the cables on fire in your walls.
Beyond that, most plugs in homes are NEMA 5-15 outlets, which also limits the output of a single plug to 15A. If a manufacturer wanted to use a NEMA 5-20 plug to get that extra 5 amps, you’d need a different receptacle and thicker wiring to safely use it. Since most people don’t have 5-20 plugs, there isn’t really a reason for manufacturers to make them.
All of this is why pretty much every electric kettle made to work with the US electrical system is slower than ones made for 240V systems. Also, they all take about the same amount of time to heat a specific volume of water, so cheap ones are going to do just as good of a job as expensive ones.
All of these same limitations apply to space heaters as well, since they are essentially doing the same thing.