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(Reposted because the orginal exceeded the forum
size limitation)
I don't have a watt meter to verify the numbers,
but the nameplate indicates that the running watts for the fridge is 750W
"full load" and for the freezer 630W. I DO know that when DTE is
"off-of-the-grid" (a frequent event around here) and I'm running on a 5KW
generator, that the load of the fridge and freezer on the generator is
noticeable - not a lot, but noticeable. A 100W lightbulb is not
noticeable. Of course, much more for startup - I'm not talking about
that. You start these up one at a time with just a 5KW
generator.
Also, by design, energy star appliances run most of
the time - my estimate is better than 70% (based on my ears). My previous
Maytag ran more frequently than my current Kenmore. (I will never purchase
another Maytag appliance - they refused to honor the service contract 6 months
into a 3 year contract; no wonder why the Maytag repairman is lonely.
I had two Maytags back to back and they each only lasted 3 years).
As a "check" on this, refer to any one of the
generator sizing charts
These sites show numbers in the ball park of mine,
with starting wattages 2 or 3 times these numbers. The starting
wattage part really isn't relevant if you are tied to the grid or have
battery backup with a large enough inverter.
So the total running load is 1380W.
Adjusting for the 70% brings it down to about 1KW.
I based my statement on the PV system running at
rated capacity for 8 hours per day (much more optimistic than your
number). To run a 1KW load for 24 hours per day, you need 3KW at 8 hours
per day assuming no conversion losses (not a good assumption). That
provides just 100% of the capacity for these two appliances.
If I used your 4.3 hours for Detroit, then there is
a shortfall of nearly 50%.
My 1KW average gives me 24KW-hours per day, or 8760
KW-hours per year. Half this (for one average appliance) is 4380KW-hours
per year.
This is around 5 times the number you used from the government table. Alright, there is a pretty big gap. But I am
pretty comfortable with my numbers based upon nameplate, personal observation,
and generator sizing charts (3 independent sources). And for the converse,
I don't believe a refrigerator runs on 90W. (your 800 KW / (365 *24) =
91.32W)
When I flip on a 100W light bulb, the generator
does not react to this. With the refrigerator, there is first the starting
blip, and then a decided load. Conversely, when you switch the bulb off,
nothing. When you switch the refrigerator off, the generator
reacts.
I have an old Maytag compressor (actually not
that old since it only lasted 3 years) with a manufacturer's fact
sheet (Embraco 12001834) that indicates the compressor alone consumes
311W. Then you have a number of fans and frost free heaters, and automatic
defrost (twice a day). The freezer is not frost free, so presumably it
runs more efficiently so long as one is conscientious about manually defrosting
it.
The only way I could be more factual is if I owned
a watt meter. Someday I will get one.
Using my numbers and a couple of different internet
sources for DIY solar panels, just buying the solar panels (4KW worth) as
components would cost $20,000 ($1000 per 200W panel at 18V), and then
you have to buy the batteries, controls, an inverter and some pretty heavy ga
copper wiring. And this is a DIY cost; if you have to hire a licensed
electrician - then heaven forbid.
This website shows the payback is well in
excess of 40 years for Detroit, and this assumes no maintenance or replacement
parts (batteries). I haven't heard much about 40 year batteries
before.
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