Coffee. Electric coffeemaker. Not the least bit efficient. First of all, any inverter worth it's salt to deliver enough power is going to suck on that battery 'till it looks like a raisin. This is not a fine-grained critique - the coffeemaker is death to your small system.
Can you use maybe a Melitta for this chore? Boil water with dead dinosaurs, then pour the water through a filtered cone? Using a regular coffeemaker in your circumstance reminds me of a very stern master chief, lording over us and a couple of us scrubbing the barracks floor with tooth brushes.