Here is my latest project a 2500/5000 watt inverter with two group 27 marine batteries.
Two group 27 Batts at 90 AH Each or about 2100 Watt Hour
Cobra CPI 2575 2500 Watt Continuous / 5000 Watt Peak
0000 AWG Welding Wire (see http://www.n1ir.com/2014_08_01_archive.html for why I use 0000 AWG)
1/2 inch copper pipe as bus
Works great powering up the forced hot air furnace, handles the 2400 Watt Start-up for the blower without a sweat and keep the furnace going at 960 Watt running. I figure a run time of 15 min 4 times a night, this set-up would last about 2 nights without recharging on paper ignoring losses and efficiency, in practical application I would only rate it at 1 night.
Would work really well with electric blankets (180 Watts)
*** Note: if connecting battery in parallel use the same type and age battery. If Different age or type please use an isolator pack.