Calculating KWH

Brian, your calculation method is correct but you forgot that 1 KiloWatt = 1000 Watts so;

4 x 80 W x 5 hr = 1600 Watt hours or

   1.6 KiloWatt hours

Here is a web site that will give you the number of hours of equivilant full rated charge of a PV array depending on; region, season, and orientation of the PV array. All you need to know is deveation of South on a compass from solar South for your region. Something I have not been able to find on the www.
A simple procedure I use to determine the basic size of an off grid system using all vac loads -
First add up the expected load for a 24 hour period in terms of kWh's.
Second choose a nominal battery voltage.
Third divide one by the other and multiply the answer by 5.
Example - 4 kWh / 24 x 5 = 833
Thats a battery bank of no less than 833 amp hour capacity at 24 vdc nominal. Its a good idea to add at least 20% for inverter inefficiencies. Which would be a total of a 1,000 amphours minimum.
Now to size the PV array using that same example of 4 kWh and going by the shortest day of the year with the PV array facing solar South tilted to an angle equal to latitude plus 15 degrees in full Sunshine from no less than 9:00 am to 3:00 pm in central North Carolina which gives me 2 hours of equivalent full rated charge a day - whew! - I take 4,000 / 2 = 2,000
Thats a 2,000 watt PV array. This would give me plenty of power in the summer, espeicially if I tilted the PV array to latitude minus 15 degrees, plus all of the above. In the winter I might would need to run a genset to makeup for several cloudy days in a row say about 4 days if I was being conservative.
http://rredc.nrel.gov/solar/old_data/nsrdb/redbook/atlas/  

Your math checks out OK.

However, there is one big red flag for me.  A 1,000kW genny is gigantic. I would tend to believe that you are looking at a 1,000 Watt (or 1 kiloWatt)generator.

In that case, your revenue would be 81.6 cents a day.

A typical burn rate on DIESEL is going to be somthing around 80gph at full load, and about 55gph at 3/4 load. My guess is that WVO would be a higher burn rate, but I do not know what that percentage would be.
I would run my numbers using both figures.  The unit will last a lot longer at 3/4 load (750kw) than at full load.
I hope you are factoring in some type of large oil storage tanks. At full load, running 24/7, you will be burning about 1,920 gallons a day or aobut 13,440 a week.