Originally Posted by 4dsx4
I was thinking 1000 watts was about 9 amps?
Something wrong with my math
I wanting to run an 850 watt coffee maker
Your math is ok, but you are mixing up AC volts with DC volts. So yes, 1000 watts is about 9 amps AC. But you need 12V DC to run the inverter and it takes roughly 10 times the AC amps or 90 amps DC to supply 1000 watts. Way above what a cigarette lighter outlet can supply.
If you need more than about 150 watts then you probably need an inverter directly wired to your coach batteries.