Well it's sunny and 12°C/53°F outside. I'll tell you that my SPVS is working and it does run, albeit only for a few seconds, every 20-30 secs. So I think the 20°C/68°F criteria is for interior temperature. Also keep in mind that I'm in a high latitude (1/3-1/2 between the CAN/US border and the Arctic Circle!). Those who think it only works in Texas might wanna reconsider their thinking. It can warm inside even though the sun angle is relatively low.
