Makes sense. And I have no problem buying a second Powerwall. But, the California 2020 fire code that requires systems over 20 kW are 3 foot from any wall or each other. That is not going to be easy or maybe not feasible in our home.
-
Want to remove ads? Register an account and login to see fewer ads, and become a Supporting Member to remove almost all ads.
Powerwall sizing - Essential / non-essential loads
- Thread starter mspohr
- Start date
Makes sense. And I have no problem buying a second Powerwall. But, the California 2020 fire code that requires systems over 20 kW are 3 foot from any wall or each other. That is not going to be easy or maybe not feasible in our home.
bkp_duke
Well-Known Member
Understand. Glad we got in before that code was implemented. Given how the powerwalls are constructed, I don't see much value in that code.
I agree. I have lots of outlets and lights on separate circuits (probably about 30) and collectively they don't draw much and I intend to keep them powered with the battery backup. I do need to exclude the 240v circuits (hot tub, dryer, car charger, etc.) but these are only a few circuits. Right now we have a gas range which, of course, doesn't take much power so we'll be able to cook.
This is an article written by the CEO of a company that sells StorEdge/LG Chem systems. The premise is that if you only have 2.5 kWh left in your batteries at the beginning of the evening, they won't last overnight. The main attraction to me for the Tesla Powerwalls is that you actually got a reasonable amount of energy for the price. With a sensible reserve set, I can go indefinitely off the grid in the summer months with my two Powerwalls. I'm not sure where the 20+ kW and 40+ kWh numbers come from in the quote above, but it seems to be deliberate worst-casing to make Tesla appear worse in comparison to the systems they sell. See also the chart in the article highlighting "delays" in Tesla battery shipments.
bkp_duke
Well-Known Member
Each to his own, but we can easily do 20+ kwh overnight. Without A/C or an oven running, we probably only consume about 10kwh per night, but with either of those in use, we have been know to fully deplete 3 PW2s (40.5kwh).
In winter, my house averages about 60 kWh /day and solar only generates 30 (on a good day). I definitely need to manage loads with grid failure.
(Summer it's the opposite. Use 30 and generate 60)
Merrill
Merrill
This makes no sense, how do you mount 2 powerwalls with nothing to attach it to and space them 3 apart. So they will be standing alone and how do you support them.
I assume you would have to anchor them into a poured concrete pad with lag bolts coming up from the pad. Similar to how they mount the gear at a Supercharger. The pads would be 3 feet apart and 3 feet from the side of the home. I don't think we have the space to do something like this so we would likely have to limit our battery system to one Supercharger to get under the 20KW trigger.
I agree, crazy talk. Given what we're investing in these systems I wanted the whole house on the backup and I wanted to be able to run off the PWs completely for at least a given daily peak period. I could have done it with 3 PWs, but went with 4 so I had margin to play with to insure if needed I could run at least two of our 3 AC units (2.5, 3 and 4.5 ton units) which in the summer in AZ run sometimes for 15 hours. So the whole house can be run through the Powerwalls, but I carefully control (thorough home automation) what peak loads hit the PWs during peaks. Off peaks the grid can supplement. During an outage, I'd just go switch off certain circuits to insure they don't drain the PWs instantly. So while I can't avoid running the AC during the entirety of our summer peaks, I can run them enough with the Powerwalls during peaks to zero out my any peak usage, and still be comfortable in 110 degree heat.
IMHO, while the myth mentioned above was wholly and truly accurate even 1-2 years ago, based on my experience, if the state of technology and costs for these systems continue to improve at even a fraction of the rate as they have over the last 5 years, I think the myth of powering a whole home on solar & batteries will become the myth within the next decade - although maybe not with two big Tesla's autos sitting in the garage. The main problem is it takes money to do it right up front in order to make it through to the breakeven point - which is still not attainable for many. I feel like I'm 2/3rds of the way there even with 3 relatively large AC units, and a Chevy Volt to charge with an investment break-even point estimated to be less than 7 years - and that was unthinkable just a few years ago.
For now, for me, the myth holds that I can't run my house 24/7 off only solar and lithium batteries because of summer AC usage, but for the fall/winter/spring 6 months of year, I'm seriously close, close enough to think it's coming in my lifetime.
Last edited:
Merrill
Merrill
Yes, so how many people have an area to do this close to the main panel. If you have a three car garage you could do it.
I think I could do out if it could be done outside. I have a 15 X 10 concrete slab outside my garage. Previous owner put it in for a car. I use to hold my garbage cans. It is adjoins the outside wall of the garage that houses the PG&E meter and two switch boxes. I assume that wall is where Tesla will mount the solar cutoff and other gear. It would require cutting up the pad a bit to get run the connections to the wall. And then the powerwalls would be out in the weather with no overhang. Not sure if that is OK.
In light of the silly regs in California, my guess is that the next version of the Powerwall will have 19.9 kWh of capacity and a charge/discharge rate of 10 kW. Most people in California will install just one. Also, Tesla should make it easy to supplement the Powerwall with a Cybertruck for backup purposes, perhaps by adding a 240 VAC inlet for emergency charging.
Over Thanksgiving weekend, we had more than three feet of snow and power outages totaling about 30 hours, with no recharging of our two Powerwalls between outages. We had about 42% charge remaining in the Powerwalls when the outages were over with. However, we're still using a forced-air gas furnace, not a heat pump. We'd need more battery capacity, ideally in the form of vehicle-to-home, to be prepared for winter outages without natural gas.
Over Thanksgiving weekend, we had more than three feet of snow and power outages totaling about 30 hours, with no recharging of our two Powerwalls between outages. We had about 42% charge remaining in the Powerwalls when the outages were over with. However, we're still using a forced-air gas furnace, not a heat pump. We'd need more battery capacity, ideally in the form of vehicle-to-home, to be prepared for winter outages without natural gas.
That would be great! And very Tesla.
- Prevent us from selling cars in your state, boom will let people buy online and deliver to their door. Put 20 KW limit on easily installable batteries, we come out with the PowerWall 2+, 19.9 KW and 10K
- Vehicle-to-grid is available in some countries in Europe. And Tesla would be the company I would expect to do it first in the states since the can create a micro-grid with their cars, solar, and energy storage.
Similar threads
