Need help estimating usage cost for a whole house generator

At least $30/day to run a whole home generator on natural gas.

it will tell you on the cut sheet for the model generator you are looking at. For example a 22kw generac burns about 3 gal/hr of propane at load. Look up the specs on yours

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1 CCF equals 100 cubic feet

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Thanks for fact sharing, but my Google Machine was on top of this one.

1mmbtu is 300kwh.
Guessing your residential prices are close to $10 for that much gas and $45 for that much electricity.
21% efficiency overall would be super optimistic though.
I think you’d optimally have electricity beatable if gas was $1 per ccf and electricity was over $0.20 per kWh but even that doesn’t account for wear/tear or maintenance.
Beatable doesn’t mean beat either. Still have to have generator and appliances ideally sized. My best guess is you’re running at 10-12% average efficiency and electricity costs would need to be over 30 cents to be beat by $1/ccf gas. This makes running gas approximately 2x electric price after subtracting the service charges that you’d pay anyway.

If you are worried about the cost to run the generator you are splitting hairs.

Natural gas is cheap and if the generator is running, you won't be using electricity. Trying to calculate the cost of the gas is pointless.

Having a whole house generator is a matter of convenience and peace of mind. If cost of gas is a concern, consider that it may run for more than 6 hours about once every 2-3 years in our area. 99% of your usage will be small power blinks/brief outages.

I have had one since 2019 and only twice has it run for more than a few hours.

exactly

is anyone really concerned enough about the cost of gas when the power is out to not run the generator? That’s what it’s for

the cost of the generator and gear will never be recouped so you will be underwater on it forever. Let it run

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Seems like it would be useful to know what to plan for during extended power outages, no?

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It is useful. I just think you're trying to compare something that isn't comparable so to say.

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If my current electrical consumption is 50 kWh per day, how do I convert that to a consumption cost of a natural gas whole house stand-by generator where natural gas is measured by centum cubic feet?

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This is not directly proportional. You are charged by the kWh from the power provider. On utility power, as your load goes up, the meter spins faster. Load goes down, meter slows, no load meter stops. However, a generator runs at max RPM no matter the load you are pulling. That said, your gas meter is going to spin at a pretty much constant rate. Even if everything in the house is off, that generator is still running at max RPM and the gas meter is still spinning.
Sure, a large load such as kicking central air on will load the generator slightly and it may consume slightly more fuel but not enough to make a difference or worry about calculating.

That said.....
I have a 20Kw Generac on my home. It cost me roughly 20-24 dollars a day (24hours) to run. FWIW, when I'm on generator, my AC is normally turned way down like to 66 because I'm paying for the gas to run the generator anyway.


ETA:
Think of it this way. Your paying by the hour to run the generator, not really by the electrical consumption.

easier to do this if you get the generator specs. Find consumption data and kW production data.

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However, a generator runs at max RPM no matter the load you are pulling.

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The fuel consumption rate changes drastically with generator load. Idle fuel consumption is much lower than when running say at 75% load.

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I’m just trying to do a more thorough cost/benefit analysis to an alternative.

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I think the issue you're trying to nail down isn't going to be as accurate as you're hoping for without more specifics from you.

Someone already offered to give you usage rates if you give them the model of generator/size you're talking about. The analogy that's coming to mind is asking what kind of gas mileage can I expect from a new vehicle. Are we talking about a diesel 1 ton all wheel drive dually or a hybrid prius?