Rick - I plugged the .5 amp power supply while it was hot, but then later tried it from a cold start. It did heat it up to the same temp, but it is not quite as hot as the 1.5 amp power supply. You can get vapor from it but it is not as quite as thick when comparing with the 1.5 amp. I will not be recommending the .5 amp power supply for normal Toasty Top operation. It is close, but not quite enough for me. The 1 amp Zap power supply does have enough as mom has demonstrated. Will be interesting to see how well a .8 amp power supply works. Orestes - I have connected my Toasty Top directly to a 12 volt 5 amp hour power wheels battery and it lasted almost 4 continuous hours starting with it hot. Polarity of the wires don't matter.