BobG said:
Is there a rule of thumb for cost of generator power? Electricity is
about 15 cents per KWhr around here. My generac 3500W was using 3/4 of
a gal every 2 hrs last time the power was out for a couple days
(hurricane a couple years ago). Thats about $1,13 an hr at ($3 a gal)
for 3.5KW or 32 cents per KWhr. Anybody doing better than that?
As has been mentioned, you were probably not actually loading to the
capacity of the genset, and therefore cost more per KWh than you got
above.
Diesels can do somewhat better, in part because the fuel use scales more
reasonably with load (half load is nearly half the fuel consumption of
full load - not the case with gasoline/NG/LPG) and good ones simply
don't use as much fuel per KWh regardless of load - but they vary
widely, which is to say that some are fuel hogs, too. Diesels should
always use less fuel volume per KWh, simply because a gallon of diesel
has more energy than a gallon of gas. However, at the moment in the
Northeast US, I think even no-tax (off-road) diesel is more expensive
than gasoline (always taxed), and the generators (particularly good
ones) are far more expensive. Not a very good deal if you only use it
every two years or so.
A good diesel set under 20 KW can do a KWh on .06-.08 gallon of diesel.
Bigger ones can do even better, but are not reasonable for a small
individual user (and not that efficient at small loads). Some of the
sets for which data are easily available show interesting patterns, such
as essentially the same fuel consumption (gallons per hour at full load)
for 6KW sets and 10KW sets, meaning the 10KW set is a lot cheaper to run
in that case.
