Insulation done! Shop heater questions. Electrical gurus.

Hi,
Before I got into computing I was in HVAC/R but that was a LNG time ago.
If my memory serves me correctly and the principals haven't changed I think you are on the right track.

As I understand it the electric bill is calculated against consumption of Watts. So if your heater consumes 1500 Watts an hour your bill could be a little lower using 240v over 110v. Typically 240v is more efficient than 110v because the amp draw is decreased which could result in lower line temperature which keeps the resistance value down essentially wasting less watts to resistance. Watts are calculate by multiplying amps and volts, keep in mind that amp values are influenced by resistance ,or Ohms.

Air movement is very important to maintain even cooling. Heat travels from a warmer to a cooler substance so it could take time to spread. You can improve travel by using air circulation to improve heat convection.

Regarding heat pumps. As I recall the principle is that they are air conditioners operating in reverse. That being said outside ambient air temp has a huge impact on the effectiveness of the heat pump. By me here in the NE we get down below 30 regularly and heat pumps struggle to scaveng heat from the air outside and are usually supplemented with electric heat strips.

As I said it been a while since I've been in the field and technology has advance so keep researching. I hope this info helps.

AlV