Since I was also curious I did another test with the hot air gun on the second level and the waveform indead looks much better (I also calibrated my scope, doh):
I also checked the reported power in the Iotawatt and my power meter and I would say it was reporting inside an acceptable margin of error. I also hooked up the hot air gun on level 1 with the SCT006 and about 10 Ohm resistance but it did not really look different to the 30 ohm (speaking about the shape of the waveform).
Now I am wondering how common are such kind of appliances? I want to have a fairly accurate system but I am planning to do per room measurements with the SCT006 in a 3-phase system with 3 SCT013 on the main phases coming in in addition. So from the findings here the measurements of the main phases coming in should be quite ok, but depending on the kind of load the per-room measurements may not. The question is how likely is it to see this type of load as the hot air gun. I am not keen to buy a complete new set of CTs, but seeing an error of over 50% on the SCT006 does have a bitter taste to it.
@Giraffe: nice findings, I dont get everything, especially in the first one, but I clearly see the diode in the second one, in line with the lower power mode.