Ted’s right. Moreover they use a class D output stage and cannot handle power factors of less than 1 without even more distortion. If you try and power anything with a PF of 0.7 (common for amps and preamps) you’ll get a nasty divot out of the peak of the sine wave under any heavy current use. These are fine as intended, as battery backups, but not to replace a real regenerator like a Power Plant.