I bought a Generac 4000XL from Home Depot a year and a half ago. It is noisy, no argument there, but it functions as intended. It will start and run my 15k ac unit and microwave oven along with the converter load and will run all night on one tank of fuel. I had a local fabricator/welder build a strong mount to hang it on the back of my 5er and an upholstery shop stitch up a tight cover to protect it. If you or a friend or family member are an eligible senior citizen Home Depot, at least in my city, offers a 10% discount on Tuesdays.
We'll both be overwhelmed with all the replies that claim a Honda/Yamaha is better and quieter and I don't disagree with them but for my needs and what I wanted to spend the Generac is a practical solution.
My 5er was built generator ready with a ventilated compartment, automatic changeover switch and other equipment built-in. If I was willing to spend the money an Onan would be the ideal solution but my air conditioner and microwave like the ac power made by the noisy and cheap Generac just as well as they would like a Honda or Onan. It's your money.
Harvey