during a extended outage my concerns are, Fridge, freezer, Water pump, and furnace fan. and that puts me in the 6.5Kw range.
Two comments:
1) Sometimes less is more:
As long as the outside temperature is reasonable, you need about 2KW to "run" a house on a temporary, emergency basis. Choosing an inverter-type single voltage (120Vac) generator with modest power output (~1.5KW to 3KW) has a very beneficial effect on fuel consumption if you are operating from fixed fuel stores (for example, gasoline, diesel, or propane). The net effect of using a small generator during a power outage is that less stored fuel carries you longer. For this reason, beware of getting a larger generator "just in case you want to power more stuff"; the downside is that you will need to store more fuel, and replenishing fuel stocks during a power outage can range from problematic to impossible. With community-supplied natural gas as a fuel, this is not a problem.
2) Peak loads can exceed average loads by a factor of 5-10X:
The problem with sizing a generator to run every load -- including "big loads" -- is that the eventual solution is very inefficient when supplying typical normal loads. For example, a 240Vac deep well pump can draw 50A on startup and 15A when operating. On this basis you will need a fairly large split-phase (120/240Vac) generator capable of providing at least 3.6KW continuous and up to 12KW peak. Specifying such a big generator means that during typical, light load operating conditions (e.g., less than 2KW) you are using a lot of power just to keep a lot of rotating mass in motion. And that means high fuel consumption. Again, if you are using stored fuel, that can be a problem during an extended outage. Sure, it's nice that you can use the well pump or the A/C any time you want, but in the end, fuel supply will be the problem.
Just as an example, a typical(*) 5.5KW gasoline generator uses about a half gallon of fuel per hour at half load (2.75KW output). That's about 12 gallons of gasoline per 24 hours at half load. If you were to only run the generator 12 hours per day, you need 6 gallons per day, every day, for the duration of the outage. How much gasoline do you want to store?
wrooster
(*) e.g.,
http://www.northerntool.com/shop/tools/product_200370713_200370713
