The electrician may be including items that you can do without during an outage. Many of us (as said above) get by with a much smaller gen by using load management. Just use what you need to get by and not try to power everything in your house as if on grid power. You can supply power to everything, but you don't use everything at the same time...unless that is your goal. Are you willing to load manage, or are you trying to power everything as if on grid power like a whole house generator does? As mentioned above, big generators use huge amounts of fuel even when running with little to no load.
We would still like to know which generator models you have narrowed your search to. For example, the
iGen11000DFc and the
GM11000iET can both provide about 8,000W on propane. However, if you actually need 10,000W, then you would need a much larger generator. Also, you should not run a generator near its full rated load for very long because that will shorten the life of the unit. And, don't forget loads that draw high starting (surge/inrush) current such as an A/C unit. Some of those loads can be made more generator friendly by installing a soft start such as an
EasyStart.
You can also consider running two identical generators in parallel. That gives you the ability to shut one down during light load conditions, such as nighttime, or when the weather is cool enough that you don't need the A/C, and save fuel at the same time. Having parallel units also provides redundancy should one generator fail or it needs to be taken offline for maintenance such as an oil change. You would still have the other gen supplying power to the house.