Re: The Physics Behind the Spanish Blackout

On 6/13/25 3:44 AM, Don Y wrote:

On 6/13/2025 2:18 AM, KevinJ93 wrote:

Yes, definitely possible - that would possibly cost $5,000 or equivalent to one year's consumption without solar.

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Neighbor just had her roof replaced.  Remove the panels.  Replace the roof.
Reinstall panels.  Wait for inspection before going back online.
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I've not asked her what the change in electric costs were (she is "lucky"
in that she could leave the house unoccupied during the day and just
hope it doesn't get TOO hot inside for the ACbrrrr to bring it back
to a livable temperature LONG AFTER she had returned home from work.)

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I don't see why the power to the house would be affected. The Solar array can be completely isolated from power. In fact around here it is required that there be a well-marked accessible isolating switch on the exterior of the building accessible to emergency personnel. There is also a separate isolating switch for the battery system.

 The panels had to be removed from the roof (typically, the only place where
installation is supported) in order for the roof to be replaced (re- shingled).
 From that moment -- until the inspector re-approved the reconnection of
the panels -- she was operating entirely on utility provided power (because
her panels were in storage!) ... yet still on the ToU tariff.  I.e., the
entire reinstallation of the panels had to be re-approved before being allowed
back into service whereby she could begin generating some of her own power.

Aah, I read your previous statement as the power to the whole house was turned off, rather than just disabling solar.
Regarding the re-approval required, the US is renown for excessive red-tape in permitting. It seems to be that the US costs about twice as much as any other western country to install solar just because of the bureaucracy involved. The re-approval requirements will vary depending on your locality.
I have never done it here in California but I had heard some cities are a lot worse than others. They also add installation requirements locally that go beyond the statewide rules. I had to add a fire detector over the batteries that was tied into the house alarm system.

We looked at the ToU tariff thinking we could easily shift our consumption
to leverage any rate reductions.  But, most of the cooling load (which is most
of the load!) happens during on-peak hours (3P-7P); and the rate is ~50% higher
per KWHr during those times.  Hard to imagine the cost in comfort to appreciate
any real savings!

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I run off batteries/solar during the peak time in summer.

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It would be hard for us to do that for all of the time that
refrigeration is needed.  E.g., it is now almost 1AM and it is
still 85F outside.  It was 95 at 10PM.   And 98 at 7PM.
110 this weekend.

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When I say "peak time" I mean the peak tariff time which you said is 3pm to 7pm - just four hours, during which there is probably a fair amount of solar as well so not completely off battery.

 We have 6.5 useful solar hours.  Likely something like 10-4.  Peak usage
(for the utility) extends to 7P.  I.e., refrigeration is in high demand
for the entire "peak rate period" (my numbers trying to demonstrate that
7PM isn't anywhere near the point where you could consider NOT using
refrigeration -- so 3-7 most definitely would also have a heavy cooling
demand)