This thread is very old, but still very much valid. When considering a backup generator, the primary concern should be backup and without fuel security, you really do not have backup. That can be accomplished by either heating oil (diesel) or propane. Natural gas should not even be considered because you do not have control of its supply. Now the argument is between propane and oil. Propane requires a large tank under pressure and oil requires a simple plastic tank. Oil has 50% more energy by volume than propane, so storage takes much less space. Propane won't vaporize in cold temperatures. Although gasoline is a choice, it is expensive and dangerous to store in volume and perhaps even illegal in your community.
You now have to consider noise and the slower the generator runs, the quieter it is. Generators that run on gasoline or gas are usually 2 pole and have to run at 3600 rpm to produce 60 Hz power, but 4 pole gen sets run at half that speed 1800 rpm. Guess what's more quiet? The last and most important point is intended duty cycle. Most gasoline and gas engines are limited duty rated whereas most diesels are continuous rated, not all, but most. In all cases there is a limit to run time vs oil change requirement and it is surprisingly short. However, diesel engines usually have a larger oil pan capacity and are capable of longer run duration before oil changes.
After all these considerations, my solution was to convert a 10' steel shipping container to a generator house installing an overheard "I" beam and trolley, LED lighting, Filtered air inlet air ducting and cooling air exhaust duct for the radiator. I also installed an output switch box with circuit breakers and ground fault interrupters. There are feed waterproof output connecters on the outside of the container as well as a fuel fill connector that leads to my 6000 liter heating oil storage tank.. My chosen generator is a 3 phase 15 KW (20 KVA) diesel with a 200 liter fuel tank in its base. I have also installed a fuel transfer pump and a battery tender. The converted container is independently fed by the house electric power and the output connectors feed two transfer switches, one for me and one for my neighbor if he needs it. These transfer switches are installed at the house power entrance point in both houses. I ran insulated exhaust pipe from the genset to an internal muffler and then outside to a much larger muffler for noise abatement. When running it can barely be heard at 50"
As an added bonus, there is enough room left in the container to house an emergency food supply and a 4 cylinder 300 BAR air compressor for my PCP tanks.
