Don't know much about all the various methods
that these modern "space heaters" use, but I do know the newer ones have safety features and far more user controls than when I was growing up.
Also, Aaron accurately points out that the actual consumption of 1500 watts is going to result in the same amount of electrical load (and consumption), regardless of how clever the device uses that power to create and distribute heat.
I have one of these that I purchased last year.
Lifesmart 1500-Watt 6-Element Large Room Infrared Bulb Heater with Remote-ZCHT1001US - The Home Depot
Admittedly, I do not live in the most frigid environment.
But this little fella can heat up a few hundred square feet easily enough. And I can go to sleep without the fears I had as a child that the dog might catch the house on fire with the space heater.
This one rolls around very smoothly. And it projects the hot air upwardly at about a 45 degree angle. So sitting on the floor and set a few feet away from the bed, the warm air directly hits me where I'm laying.