yep nothing wrong with an extension cord. I have a 50 footer I keep with me as I tend to have to park in structures for my work and sometimes the plug is a distance away. never had any issues using it.
2012 Crystal Red Volt, All options except Navi.
VIN#C-3498 Born 09/11= RIP 11/28/11 with 1600 miles.
2012 Blue Topaz Volt/ Loaded with every option adopted 1/12/12 with 9 miles
VIN#C-7622 "AC2DC" EV Personal best= 58.1
Current lifetime MPG=103
2012 Toyota Prius Plug-In
Adopted 11/5/12 with 3 miles
"American by birth, Teamster by the grace of God"