Generator can hold 12.5 L of fuel in total.
Min Consumption 1.5 L per day or 0.0625 L/h = 8 Days with max fuel

--- Common 24/24 Appliances ---
Lights -> Consumes 0.002 L/h so with 1 generator running at min consumption you can place down 31 Lights
Minifridge -> 0.13 L/h or 3.12 L/day -> Means your generator can last 4 Days with one of them
Popsicle Fridge (the only full freezer in the game) -> 0.08 L/h per side for a total of 0.16 L/h or 3.84 L/day -> Means your generator can last only 3 day and 14 hours
Industrial Fridge (the most common fridge you can find in food stores) -> 0.13 L/h or 3.12L/day -> Means your generator can last 4 days
>>> Note that you can have many generators connected to your house that are running at the same time. Beware that you will consume on average 1 electrical scraps per day per generator and you need to have it in your main inventory with a screwdriver to be able to repair the generator (if you have the scraps in your backpack it won't work)
--- Calculation for an Average Setup ---
In long runs usually you want to have:
1 x Popsicle Fridge - For your farmed vegetables
2 x Industrial Fridge - For your main food that you have to consume in the month. Usually 1 is better to be used for already cooked food and the other for ingredients you have to consume ASAP
30 x Lights to have a good illumination inside and around the base so you don't risk to get ambushed.
Total Consumption: 0.48 L per hour or 11.52 L per day
This means that you need at least 2 generators running at the same time if you want to maintain this setup for at least 2 day without refueling it.
This also means that if you want to have 8 days without thinking about it you will need to connect 8 generators. But careful in this case you will use too many electrical scraps. So my advice is to have 4 generators and refuel them every day or 4
--- Tricks ---
- Don't worry too much about the generators when you go out of the town. Once you get the house our of loaded area your generator won't consume any energy and you don't need to worry about it at all. I'm not sure the exact area range but I think is somewhere around 100/200 tiles.
- If you place the generator on a roof and cut out the path to get there using staircases but instead you have to use the escape fabric it won't attract zombies because they can't create a path to follow in order to reach it. Personally I destroyed the staircase going between the 1st and 2nd floor.