Re: energy in UK

On 4/17/2025 12:05 PM, KevinJ93 wrote:

<...>
 > Here, the issue is the high PEAK demands that the ACbrrs place on
 > individual
 > subscribers.  We could probably get by on a 3-5KW plant -- but, only if
 > we could store and deliver for large loads (I think the ACbrr is ~14KW).
>
That's a very large residential A/C. Our 4-Ton unit (48kBTU/Hr) takes about 5kW and suffices a 2,900 sq ft house in northern California. (Don't you like all these antiquated units!)

>
That's the startup load.  An inverter for a (pure) solar solution would
have to tolerate that for some large fraction of a second/seconds.  I.e.,
you would NEED to be grid-tied in order to support such large loads,
even temporarily.

 14kW startup is about 60A LRA (locked Rotor Amperage). A single Tesla Powerwall 3 battery is rated for 185A LRA and it is very common to have two or more Powerwalls in a system which increases the available short term power. Our A/C has a 104A LRA spec.

We don't want the on-site battery storage -- and the risks that come with it.
The sun ALWAYS shines (here -- literally).

By contrast, using minisplits -- and staggering their actions -- we could
get by with something considerably smaller.

 Yes, I like the minisplit approach - we have an 18,000BTU/Hr one for a separate room and it extremely quiet and efficient. It normally only takes 200-300W with very low inrush.

We don't like the "industrial appearance" that they (ductless) have.  Maybe
OK for a garage but not living area.
The *ducted* units are less obtrusive as they can be installed inline with
existing ductwork.  But, you have to rely on the existing ductwork
being compatible (in terms of air flow, inlet, outlet, etc.) with their
deployment.
If building a new home, it would be SO much easier!

<...>
 >>
 >> UK allows up to 4kW solar generation on any domestic premises. More
 >> than that
 >
 > I don't think the *city* places limits on size of plant.  But, requires it
 > to reside on rooftops to avoid permitting, architects, etc. (of course).
>
Here in PG&E land around the SF bay we're allowed up to 10kW of solar generation without significant additional requirements.

>
It's the *mounting* that causes the additional requirements.  You have
to be able to certify that the STRUCTURE that you use (or create)
can bear the load under high winds, etc.

 Yes, we had to get the city to give their permit that involves what you mention plus features for emergency responders such as adequate access to the roof and approved means of disabling the panels and batteries with suitable signage.

The PV issues are all covered in a licensed installation (and inspection).
But, the physical mounting requires a licensed architect, load analysis,
soil stability, considerations for wind, etc.  All justifiable but all
make it harder to find people qualified to do those things AND inspectors
comfortable with "non roof" installations.
The code, however, always has loopholes that aren't expected.  E.g., a friend
put up a 4-6 car garage as an outbuilding, on his property.  If he had poured
the slab and then erected the building atop it, he would have needed a
permit.  But, by erecting the building, first... and then pouring the slab
through openings in the walls, he got the same result WITHOUT the overhead
of the inspection and permit.  (how is his finished product any different?)
So, there may be a way to "ease the pain".  But, you don't want to cut a corner
that has real consequences.
For now, we have enough "other things" to keep us busy and throwing money
at air conditioning is relatively easy.