Heat pumps don’t work when the outdoor ambient drops below freezing. So, they switch automatically to resistance coils, which draw far more current. Overloading the grid and taking it down.
The question I have is why heat pumps don’t work when ambient temps drop below freezing as you suggested. The ground below ten feet is usually always around 75 F. So, as long as you have electricity to keep the circulating pump going things should be OK. Of course, if electricity fails you may have problems. Here in Illinois, we have many heat pump installations, and they work just fine summer and winter. I appreciate if you can enlighten me.
Not in Illinois. 55 degrees: https://sustainability.illinois.edu/geothermal-energy-coming-to-a-midwest-state-near-you-part-i/
You might want to do a little more research on ground temperatures.
“The question I have is why heat pumps don’t work when ambient temps drop below freezing as you suggested.”
Most heat pumps are try to pull heat out of the air, which is the problem with cold temperatures.
“The ground below ten feet is usually always around 75 F. So, as long as you have electricity to keep the circulating pump going things should be OK.”
You can’t get enough heat transfer unless you tap into a water source.