2 powerwalls coming soon

[Cdavismd]

I am in south Texas building a new home. I have just installed a 13.2 KW solar array and will be getting two Powerwall 2’s . I’m in line for a trimotor CT with a fairly low reservation number. Looking at the many options for electrical service contracts, there are two that seem like good options. One has net metering with the buy back from my excess solar is the same price as what I pay. With the powerwalls I am expecting the net electric bill to be very low but would go up with charging a CT. Another option that intrigues me is where I pay for any electricity from 6am until 8pm and the rest of the time it’s no charge. There’s no net metering. That means charging a CT at night is free. I am new to the EV world and powerwalls. I’ve had solar for a few years and was disgusted after hurricane Harvey that there was no power for three weeks, thus the powerwalls. To my question; which service contract make the most sense for my situation. Can I charge a CT at night using the free grid and program the house to use my powerwalls outside of the free window when solar power is not available? (Early morning, early evening) would it make more sense to go with net metering?

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[Crissa]

Yes, you can tell it to only use the cheapest power to charge with. Some of that is dependent upon how your utility alerts you to your power prices.

Though you'd be better off charging while the solar is producing than from the Powerwall. I think it can intelligently do that now. As batteries become full, they become more inefficient to charge. And there's always some loss when being stored. So charging a battery from a battery is twice the loss.

-Crissa

 

[Cyber_Dav]

When considering solar and powerwalls I visited this forum. It has more people available for this specific question.

I apologize if I am not supposed to mention other forums. This forum (Cybertruckownersclub) is much better for Cybertruck discussions, that one for solar.

 

[ajdelange]

I am in south Texas building a new home. I have just installed a 13.2 KW solar array and will be getting two Powerwall 2’s . I’m in line for a trimotor CT with a fairly low reservation number. Looking at the many options for electrical service contracts, there are two that seem like good options. One has net metering with the buy back from my excess solar is the same price as what I pay.

You don't really need the PowerWalls with a net metering program that will buy all your excess solar generation at the same price you pay for electricity. The utility becomes your battery. For example if, on a sunny day, you generate 47.8 kWh extra solar (as I did yesterday). During the time the array was producing the house used 28.8 kWh so I produced 19.0 kWh more than I used and "sold" that to the utility. During the time the sun was down I used 36.3 kWh which I got from the utility but as I had a credit with them of 19.0 kWh I only had to pay for 36.3 -19 = 16.9 kWh. Thus the utility didn't store 19kWh of energy for me. It stored the value odf 19 kWh for me and when I needed 19 kWh at a time when the sun wasn't shining gave it to me at no charge. Note that as far as the amount of energy the utility had to generate and my cost the effect is the same as if I had two powerwalls (13 kWh capacity each needed to store the 19 kWh).

With the powerwalls I am expecting the net electric bill to be very low but would go up with charging a CT.

You can do a rough calculation based on the number of mile you expect to drive in a year. A thousand miles a month is typical. Five hundred Wh/mi is probably not a bad estimate including charging efficiency so 1000*.5 is 500 kWh per month for the truck. I like to think of that as an average continuous load of 12000*0.5/(365.25*24) = .684 kW. Driving the CT that much in a year is like having an extra 7 light bulbs of 100 W each on all the time. Note that this amounts to 16 kWh per day and that as your 13 kW panel system will give you typically 47.8 kWh in a day (that number is yesterdays production from a 13.9 kW PV system) that's about a third of your daily production. Compare that to your other loads.

Another option that intrigues me is where I pay for any electricity from 6am until 8pm and the rest of the time it’s no charge. There’s no net metering. That means charging a CT at night is free.

But it also means that you don't obtain any benefit from excess generation by your solar cells. Here's where the real value of the PowerWalls would come in. If there is excess solar production it would go to the PowerWalls.

I am new to the EV world and powerwalls. I’ve had solar for a few years and was disgusted after hurricane Harvey that there was no power for three weeks, thus the powerwalls.

The 26 kWh capacity iof 2 powerwalls isn't going to carry your for more that a couple of days at most if that depending on your loading and what you are willing to shed in a prolonged outage.

To my question; which service contract make the most sense for my situation. Can I charge a CT at night using the free grid and program the house to use my powerwalls outside of the free window when solar power is not available? (Early morning, early evening) would it make more sense to go with net metering?

The answer to your question really depends on what your loads are and how they are distributed over time. The simple answer is, of course, to install enough power walls to cover your daytime load and charge them at night from the mains when they can be charged for free. Your electric bill would then be 0. But I'll be there is a catch in the fine print that would prevent you from doing that.

 

[Cdavismd]

Thanks for the input. The most likely events for power outage occur from July to mid October due to weather. It coincides with some of the best solar generation, too. I am assuming a couple of powerwalls will provide nighttime power aans solar will provide daytime power most of the year whether the grid is up or down. Charging a cyber truck on the other hand would likely require a grid supply. In the event of a power outage, a hefty generator would be handy. So suppose a major (10-20 day) outage would occur every 3 years and a few minor outages in between going forward. I’d probably be ok with the powerwalls and my solar array for the house during the outage and be saving a bunch on the monthly bill otherwise. What do I do about keeping a charge the cyber truck during big outages?

 

[Crissa]

Charging a cyber truck on the other hand would likely require a grid supply...

If you can charge a Powerwall, you can charge a Cybertruck.

As long as you're producing 1.4kW, your truck can charge. Tesla chargers can be set to charge at whatever level of power is available.

-Crissa

 

[Newton]

well I got 2 deep cycle lead acid batteries and 2 solar panels... its enough to offset my pc and tv/ps4, which r the most used things in the apt, other than large things and lights. doing what i can with what i got

 

[Cdavismd]

Ha! Maybe my life will be that simple someday. Very much like it was for me 40 years ago, other than the availability of renewable energy.?

 

[ricshaw]

You don't really need the PowerWalls with a net metering program that will buy all your excess solar generation at the same price you pay for electricity.

That is not the case where I live.
I generate excess electricity to the grid.
The utility pays me wholesale price for the electricity.
At night when I use electricity from the grid, I pay retail.

 

[ajdelange]

That is not the case where I live.

Then the comment does not apply to you. You may well benefit from PowerWalls.

 

[BigDaddy]

That is not the case where I live.
I generate excess electricity to the grid.
The utility pays me wholesale price for the electricity.
At night when I use electricity from the grid, I pay retail.

Its the same in BC Canada where we are. The wholesale rate for electricity on much of the North America west coast is the Mid Columbia rate. Basically amounts to 10% of what we are charged. Makes having a battery bank necessary in addition to the panels.

 

[Cdavismd]

I think going with the net metering and using the powerwalls would get me close to just a few dollars a month on the household power bill. Just not sure if charging a cyber truck after sunset would empty the powerwalls has r if there’s a way to use power walls for the house at night and still charge off the grid at night.

 

[Crissa]

That's a way to do it, but generally power is cheaper at night.

Is the truck not home during the day?

-Crissa

 

[ajdelange]

I think going with the net metering and using the powerwalls would get me close to just a few dollars a month on the household power bill. Just not sure if charging a cyber truck after sunset would empty the powerwalls

Definitely. A PowerWall has a capacity of 13.5 kWh. The CT's will have batteries of 100 - 200 kWh. It would thus take 8 - 15 full Powerwalls to charge a CT.

has r if there’s a way to use power walls for the house at night and still charge off the grid at night.

The object is to use the solar energy you collect to offset your electric bill. How and whether you will be able to do that depends on how your utility handles excess power you send them. If they compensate you at the same rate that they charge then you don't need powerwalls. If they don't compensate you at all or pay you at a rate much lower than what they charge you then you do not want to send them any excess power. You want to use it all yourself which means you must have a means of storing it e.g. PowerWalls. If the utility does not compensate and charges more during the day then at night then you want to use solar during the day, the PowerWalls in the late afternoon and evening and charge the BEV in the low cost time period from the utility but only after you have emptied the PowerWalls into it.