We use an EU1000i and an electric heater. We also have an electric blanket. We usually set the generator on the dock and can hardly hear it in the boat. I'll check to see if there's anyone within earshot that it might bother and ask them first but we don't get complaints; it's pretty quite. If we're not at the slip I set it in the cockpit it can be heard but it's tolerable--be careful of CO.
The problem we have is that the rating is only 900 Watts continuous and at about 800 feet we have to derate that to something less than 600 Watts if I remember right. That just barely powers the heater at its medium setting but I sure helps. I don't hesitate to let the generator run until its out of gas but when we're sleeping I usually switch it to economy mode and we just use the electric blanket. It gets a bit cold in the mountains and this is my preferred solution.