Since heat strips put out about the same BTUs as a portable heater they will raise the overall temperature about the same. When people complain about little heat from them, they aren't considering the considerable air flow from the air conditioner fan. The air temperature from the ceiling vents will be much less than from a small portable heater but there will be much more air. That flow of air that is only a few degrees above the ambient air temperature may feel cool, but just leave it on. As the temperature rises it won't feel so cool when near normal room temperature.