Tesla Powerwall

Our gas+electricity averages about $130 a month. That's no big deal.

How about you?

45 years ago the freeways were lined with beautiful vegetation. Now the whole state looks like crap, while water is dumped into the ocean to preserve some bait smelt that now only lives in tanks at UC Davis... a fish so dumb (or near natural extinction) that they have to artificially inseminate them.

A real "paradise". With housing costs 6X per sq.ft. of housing in Arizona, and an even worse ratio compared to Texas... no wonder hi-tech is easing out of California.

When will Californians wise-up and toss Moon Beam and all his co-conspirators? ...Jim Thompson

About the same here, because electricity costs drop like a rock in "winter"... and my peak bill in summer is only about $300 (all electric house). ...Jim Thompson

Thanks Jeff, and of course buying and storing energy when cheap and then using it later will end up using more energy in total. (Conversion losses and all.)

George H.

Interesting point! What are the current practical conversion efficiencies solar=>battery and battery=>AC ?? ...Jim Thompson

And that's on a 2524 sq.ft. house (single level... no stairs to fall down ;-) ...Jim Thompson

I think it is intended more or solar sites -- cut the wire (don't use The Grid as a storage medium... and avoid the $50/month charge that the utility imposes on you for that *privilege*). Of course, it means the utility can no longer count on *you* to be a cogeneration partner. So, as demands of its customer base increase, it is forced to bring other sources on-line -- at large capitol expenditures, regulatory procedures, etc.

This has been the case for a *long* time -- even without "alternative energy sources" entering the calculus.

E.g., large businesses tend to have "demand tariffs" governing the cost of their utilities. So, big incentives to "level and shift" their loads. In Denver, it was not uncommon to "make ice" (on a very large scale) in the "off hours" to lighten the load on the air conditioning plant during daylight hours. There's another "conversion loss" injected in that practice...

The utilities always want it both ways. E.g., it would be smart for them to push for a *fair* demand tariff to encourage homeowners to shift loads. But, if you do the math, it's almost a guaranteed losing proposition for the homeowner!

Ah, but it's great for *business*! :> And, works -- unless you get some "disruptive technology" entering the equation. Then, you have to LEGISLATE to make that technology impractical/unaffordable -- because your business model now relies on the artificial constructs that you imposed on the rate structure, etc.

We are told to conserve water (desert southwest). Then, rates are increased because we aren't using *enough* water to support the infrastructure, salaries, etc. at our new usage levels. And, sewer rates increased because not enough "waste water" is flowing to keep the pipes clear of debris, etc. At the same time, there is a push to encourage MORE development -- further taxing the limited supply of water, etc.

Let's always look for the *easy* solution -- the one that protects the most (monied) "interests"!

It doesn't matter. Sunlight is free!

I should have said efficiencies Grid=>battery, then battery=>AC

...Jim Thompson

True, but price drives any market. The losses will all be in the inefficiency of the various parts of the system. Grid->DC->battery>inverter->AC

My guess(tm) is the efficiencies might be: Battery charger 0.95 Battery charge efficiency 0.80 (my measurements) DC to AC inverter 0.96 [1] Total is the product of these = 72% efficiency or a 28% loss which will need to be produced somewhere to make up the difference. That's quite a large increase in utility capacity needed to run this system. The 80% charge efficiency is my guess(tm) based on my 25% -> 75% of capacity measurements averaged over a range of discharge curves. Measured efficiencies vary considerably, especially over a range of loads. That also applies to charging LiIon cells. If charged too quickly, the cells get hot, which is a sign of lower efficiency.

PowerPoint presentation on various misconceptions about LiIon and BMS (battery management system): I don't quite agree with everything in the book, but it's a good start.

OK fair enough.. perhaps it was my misreading. I thought one of the selling points was to use to defray the peak costs, by buying it cheap at night and using later.

Musk is building a solar panel plant here in my fair city. (some random news thing...

Yes, but most "civilians" don't have demand/ToU tariffs -- there's no incentive for me to delay the comfort from my ACbrrr until the late hours of the day; it costs me just as much to use it for an hour regardless of when I use it... or, what *else* I happen to be using at the time!

E.g., if I turned on EVERY appliance in the house for an hour SIMULTANEOUSLY, I would pay just as much as if I turned on each one, individually, in succession. Businesses, by contrast, typically pay based on their *peak* usage -- regardless of "when" that occurs (though there are also Time of Use registers that can impose different rates on power consumed at different times of day). So, businesses want to be more careful about what they use and when they use it. (hotels will *gate* the controls to the INDIVIDUAL room HVAC units to minimize the chance of *all* of them turning on at the same time)

There have been some (limited) attempts to impose demand tariffs, ToU tarifss and even voluntary load shedding tariffs (i.e., utility can defer your ACbrrr so it doesn't impose as big a load when everyone in the neighborhood happens to cycle on at the same instant).

However, if you've a solar installation, on site, instead of storing the surplus generation capability IN THE GRID (and being paid for that energy at a lower rate than when you later *retrieve* it "from the grid"), if you can store it on site, it is now *worth* more to you -- whatever the net difference between the price you were paid to sell it to the utility and the price you were charged to retrieve it from them.

On top of that, if you can eliminate the $50/month "access fee" by cutting the cord to the utility entirely... (that's at LEAST $6K/10yr as you know the fee isn't likely to go DOWN once its in place!)

He was looking at building batteries, here. Thankfully, that fell through (I suspect all of these are toxic soups waiting to "boil"!)

In a grid tied solar electric system, there is no battery, so the efficiency is about 96%.

However, in a battery system, it is reduced by the battery charging efficiency, which can vary radically by chemistry, charge rate, discharge rate, etc. Most of todays battery storage solar systems use lead-acid or lead-calcium batteries, with a charge efficiency of 60 to

Hmmm... Looks like I was using 88% in 2008 on this solar powered ham radio repeater estimate: Looks like it needs a tweak.

Now, if you want real gross inefficiency, see flywheel energy storage systems.

They still are, but without water, the shrubbery is not going to survive. Most government buildings have also turned off the water.

Think positive. If it weren't for such programs, some very expensive researchers would be unemployed and on public assistance. That would cost more than preserving the smelt.

Try again: Calif Median sales price = $385,000 and #1 in popularity. Arizona = $187,000 and #12 in popularity. That would make Calif about twice the price of Arizona. Like I said, I am willing to pay more to live in paradise (with or without the smelts).

Before Jerry Brown, we had Arnold Schwarzenegger (Rep) as governator. Who could ask for anyone better to clean up the mess? Cross the line and you're terminated. Well, it didn't work and part way through his

I bet a well targeted IoT attack could turn one of those into a firebomb. I'm mounting that on the wall of my house, for sure.

Cheers

Phil Hobbs

I dunno--you could look at it as insurance against freezing in the dark. ;)

Cheers

Phil Hobbs

There has been so much crap posted in this thread I haven't bothered to jump in, but this is a "fact" that needs to be challenged.

Why do you think peak usage rates are much higher than off peak rates? Because they have to have on demand capability to supply the peak usage. The rest of the time that capability is not used. This results in large costs as well as energy waste. If small scale energy storage efficiency is high enough it can potentially save energy as well as money. It all depends on the numbers and no one here bothers with the numbers when it comes to things where they have personal biases.

I've always wondered if there is any real utility to this. A friend had a thermostat that could be cycled by the utility, but statistically, it is *extremely* unlikely the entire neighborhood would run their AC at the same time unless it was a very cold night and they all needed to be on at the same time. Then you can't shed any load unless the set point is allowed to drop. In other words it would keep your house cooler than you want.

Did you miss a decimal point? I think that is $600 a year...