Any business person should logically look at all ways to save money and be more profitable without actaully cutting corners or lowering quality. Also keep the employees happy! That seems to be something many businesses forget!
 A happy employee that cares about his job and quality of work is worth 2x as much (or more) as some guy that hates the job and just wants a check, that guy often cares nothing about the shody work he does as long as he gets paid for it.

Your right, the purchase of the inverter and batteries are a business expense and tax deductible. That could really help reduce the payback time also.
 If you can work in RE credits that also is great, it could maybe even PAY besides saving.
 In business use like this, you can't afford to have equipment breaking down and causing long delays. The generator is always there for a backup if needed, but what happens if you depend on only and it breaks?
 Mostly though what I am gettng at on this part is you don't want to take a chance on the batteries failing you, right? Write them off for 3 years as a business expense if you can and then replace with new ones. But gee what do you do with these nice 3 year old ones? :)
 They been paid for, so free for home RE use maybe :)

 But that's not what I was really intending here of course, but something to also think about if it applies.
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nothing to lose

Some places (stationary off-grid) get my goat running a diesel compressor all day, every day. For years!
If they would have a 3x, 4x, 5x bigger tank, it would sure save a lot of money. Not just fuel, but maintainence costs, down time, etc.  
Honestly, it would mean going from a couple thousand gallons of air to ??? gallons.  But tanks are not that expensive.

Another thing that gets me is the compressor running, the pop-off 'popping-off',
and a generator running to charge batteries!
Who thought that was a good idea?

Don't even get me started on hydraulics!  Ever see a 80hp diesel run to power a table top scroll saw?  I have.
   end rant

I'm considering hijacking a piece of the wife's website to post 'Idiot' pics.
Hmmm.  'what not to do unless you are an idiot dot com'?
Doesn't seem fair using bandwidth and space to show that kind of thing here.

 Kinda what I wanted to do with this post was bring to peoples attention the savings of using batteries and inverters instead of just a fossil fuel generator. Even at the highest rates I ever seen for grid power, and the losses one might expect with batteries, charging discharge losses, inverters, etc.. the savings is so great with such a system anyone that can use it should. At $2.50 here a gallon for gas and higher for diesel, then figure in the employee pay etc.. as I mentioned (employee pay is the largest chunk) some contractors and business owners could save so much money it's unreal almost. I know several, but one for instance only uses like one small power tool
 like a saw maybe 2 times an hour each time 5 minutes, for total of 10 minutes per hour. The generator is a large one because sometimes he has to power a large item, but rarely. How much does he pay the employee to start a generator and shut it back off maybe 16-20 times a day. For him it would pay to just grid charge at night about a 500-800amp battery bank and use it durring the day. That is probably even far more power than he would ever use anyway, then only run the gas generator when it is rarely needed for the large items. He would still have the generator if ever needed for a backup.

10. minutes an hour for a saw, or a hand grinder, or a drill, over a 10 hour day, thats 1 hour 40 minutes of actual use. So how many amps does it take to run the inverter 10 hours no load and a tool 1 hour and 40 minutes? See what I mean. But they pay an employee at $10hr (plus extras) 10 minutes and hour for nothing but generator controll.
1. 3/4 hours at $10hr, $17.50 a day to run a generator (actualy far far more). So even if charged on the grid power at night, would it cost $17.50 per day?

Solar is good, but that is getting into alot of money for investment in equipment some small companies don't have to spare. But if they can get the basics, batteries, inverter, grid powered charger, then they can save tons of money for other stuff to add to it. Most contractors get paid by the job but pay employees by the hour. So if a job takes 2 days less time to complete, that's two days pay they pocket per job as profits. And they save that two days not by being slave drivers but by eliminating un-needed chores.

Another way to think of it, 1hr 40min more work per day is available, almost 2hrs a day free labor? Give the employee an extra 20 minutes of break time, he is happier and likes his job better because you care, you still saved 1hr 20min and got more work done with a happier worker :)
Figuring of course a 1 worker job site which many are. 4 workers, oh well forget the extra break time or go for 5 minutes instead of 20. You still save money.
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nothing to lose

"theft and vandalism is the main reason few things are ever left on the job site".
Thats exactaly why its on trailers in the midwest!  It's taken home every single night.
Think more like 8~12' box trailer that goes home with the boss every night to sleep in his driveway.

"the cost of the energy needed for the job was a very small percentage when all things were considered"
This is what I tried to say a couple times related to battery prices.
Like if we ruin $200 worth of batteries in 15 days, it was worth it, considering our options.  We are not ruining the batteries, but it seems like we are if one considers the use at low voltages, but they keep going fine.
The risk of ruining a $200 battery every week is the best option for us.
We have not replaced the batteries since before the new system was implemented.

The local thieves know I know who they are. They also know I will take time off a job to hunt down the bastards and prosecute them. I have a record of finding the idiots also.

The fuel used by a generator is negligible compared to the options. And, it doesn't draw unemployment and doesn't require matching FICA taxes, saving you another 20% or so.

Like you said, but I didn't

"I'm sorry, but I find your hypothetical solution of hiring someone to tend the generator ludicrous and doesn't help in proving your case, to me anyway, at all"

Now I know something was mis-read there :)
 Actaully I would agree with that, BUT I never said anything about hiring someone to just tend the genny. I was talking about how much you pay a worker to walk a back and forth each time it needs to be started or shut off, that is time he is not doing other work and you are still paying for that time if you are paying him by the hour, and that time adds up! That is what I was saying. Yes I know people doing exactly that also. And my figures for there site would be pretty correct too, they are not the only ones doing this, many are!
 Yes you could buy extra stuff like remote controlls, that also costs money, how many  actually use such things? I don't see many. You can start your car and unlock your doors with the press of a button as you walk out of a store, I see tons of contractors with fancy trucks and cars doing that, but they don't do it for gennies that I see in use.

Also maybe Mis-read when you said,

"I've worked here and along the West coast, theft and vandalism is the main reason few things are ever left on the job site. If the site is known to be safe then I'd say you solutions are sound but at the end of the day it may still be much easier to hoist a generator back into the pickup and haul it home."

Basically we say the same thing here. Not sure where the confusion was, maybe I typed it wrong. MOST tools and equipment are hauled on a trailer or truck to and from the job each day, we BOTH are saying that.

""Most contractors park at a building that has grid power."
This paragraph describes a possibly good option, I know it worked fairly well for you
running that one house that wasn't on the grid. But what happens when a shipment of lumber is sent that is short of material you need right now, you or someone has cut a whole bunk of 2x4 2 inches short, or you ordered wrong and you need to head to the lumber store to get a load of whatever, and you need to load a full bed's worth of lumber. All the batteries and the inverter will need to be off loaded and then reloaded at the end of the day. Also, when all is said and done, how much extra gas and "wear and tear" has the truck seen hauling the batteries around not to mention possible "wear and tear" the batteries will see?"

These I can answer real easy. First like you said, I ran a house that way, if I could run a house, then why not a jobsite :)
 I never suggested getting rid of the generator I think. Heck you may fry an inverter one day, then what? Or what if you need far more power for 2 days than normall for a specail job and your inverter is too small. Say you have to rush a job and have 3 extra guys working using far more tools? Generator time.
 Yes keep the generator same as always, just don't use it unless there is a reason you have to. So as you say, if the truck needs to leave for any reason, then you just off load the generator and run it as you would have anyway normally. Still no problem.
 My batteries are still working fine, I was driving alot worse dirt roads than most contractors normally do and I was doing alot more driving than to a job and back also. My batteries were ones I got from a scrap yard someone else threw away, and I still use them today. I did ruin two on a long highway trip, but I think I fried them charging while driving which I am not saying to do here at all. Or they may have just been ready to go, like I said someone else threw them away before I got them.
 Work trucks probably will never see a real difference in hauling the extra weight in fuel usage. It may be there, but I never saw it with my truck. Driving conditions make more difference than rather I have the batteries loaded or not, I actaully checked this myself. I made the same long trip with and without batteries loaded, no real seeable difference.
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nothing to lose

"I geuss a basic question, if generators are so good and the fuel used by a generator is negligible compared to the options, then why are we wasting our time and money trying to set up our homes on RE? Batteries and Inverters??? We are not really wasting our time though are we!"
The problem with this statement stems from trying comparing apples to oranges. Someone at home messing around with a HAWT or homemade panels usually doesn't have a deadline to meet whereas business is usually entirely dictated by one. Two very different situations.

I'm sure your systems would work but in the end you still have a generator for when, or if your proposed systems run out of juice. If the generator is already on the job, which you already said it would be "The generator is always there for a backup if needed", then why go to the extra cost and work setting up your systems for savings that I still propose are overstated.