Export/Import options for Self-powered

Export/Import options for Self-powered

The Tesla app allows Backup-only, Self-Powered and 2 Advanced modes. None of these allow you to automatically charge the battery at off-peak rates, power the house from the battery when needed, and export solar at peak exporting rates. To charge the battery you can manually set the Powerwall to Backup-only and then manually change it back to Advanced every day. Unfortunately, you cannot force the Powerwall to export excess solar, while still powering the house from the battery when needed, unless the battery is 100% charged.

It would be great if Tesla would add similar UI functionality of Peak and Off-peak in Advanced mode to Self-powered mode but with the options labelled as Import and Export.
If no Import/Export times are active then Self-powered will work exactly as it does currently.
If an Import time is active then the Powerwall will be charged from the grid and the house powered from the grid.
If an Export time is active then any excess solar power is exported to the grid rather than charging the Powerwall.

This should be fine with the power companies as grid power is not being arbitraged via the battery.
It is a relatively simple change for Tesla to make since all the base functionality is already in the app.

gregbrew | 20 mai 2020

"If an Import time is active then the Powerwall will be charged from the grid and the house powered from the grid."

Most utilities in the U.S.A. prohibits charging of the PWs from the grid, except during a weather-related emergency via the Stormwatch feature.

bb0tin | 20 mai 2020

In NZ we are fortunate that we can charge the Powerwall from the grid at any time. I expect that in the US the ability to export all excess solar to the grid when export prices are high, and power the house from the imported grid power when power prices are low, would still be useful. It is crazy that utilities would prevent charging the Powerwall from the grid since it is in their long term best interests to allow it.

gregbrew | 21 mai 2020

In SCE country (So. CA) the energy prices are so high, and the cost differentials between Times of Use are so large that you could make serious money using that differential by charging off-peak and discharging on-peak. Utilities don't want the competition.

bb0tin | 22 mai 2020

There are places where utilities do not prevent it (such as where I live in NZ), and some even encourage it. At the moment I have to actually switch off the Powerwall to export solar at peak demand times. Not only is this financially better for me but it also reduces the need for fossil fuel generation. It would benefit the owner, environment and grid if Tesla added this functionality. It is the Powerwall software which prevents the Powerwall from operating in the best manner rather than the utility. i.e. having a Powerwall makes exporting solar at peak times worse than not having a Powerwall. This is arse about face.

gregbrew | 23 mai 2020

I agree with you completely on how it *should* be done, but it's the local electrical energy utility that dictates how it's actually done, and their fealty is to the stockholders, not their customers or the environment.

Ain't capitalism grand?

bb0tin | 23 mai 2020

I understand that there are utilities in some places which prevent a Powerwall from exporting stored energy to the grid. However, I am unaware of a utility preventing solar being exported to the grid rather than charging the Powerwall. You simply need to turn the Powerwall off to make this happen. In NZ, there is no utility or regulatory reason to prevent what I suggest from being implemented. It is purely a lack of functionality from Tesla. This lack of functionality is causing more fossil fuel power to be produced than necessary. i.e. the Powerwall is acting to increase emissions rather than decrease them, which is the opposite of sustainable energy. I find that just crazy.

gregbrew | 24 mai 2020

I'm not aware of any prohibition the the States to disallow exporting solar-produced power to the grid, just from the battery.

There are utilities in the States that don't meter power pushed back out to the grid from any source. One such example installation has been described previously on this forum. This acts as a pretty strong disincentive to provide excess power back to the grid, but doesn't prohibit it. That would really suck to be providing uncompensated power to your neighbors, via the grid, and have the utility then bill them for it.

Tesla-David | 24 mai 2020

I live in Edmonds, WA and have exported on average >50% of our solar PV electricity back to grid over past 8 years. They pay us for the excess electricity ($0.54/kWh) which has helped us pay off the relatively hefty cost of our 2012 installation. This incentive amounts to a maximum of up to $5,000/year, but those incentives will sunset at the end of 2020. After that excess electricity exported will be banked against utility grid use during winter, when we do not produce enough electricity off our solar PV to cover our needs. We operate our two PW2's in self-powered mode and can operate independent of grid for 9 months of the year. No restrictions from our utility on exporting solar back to grid.

gregbrew | 25 mai 2020

SCE has offered net metering for decades, with a single "True-Up" bill each year. That sounds like what you'll be moving to. In SCE country, if your production exceeds consumption over the entire year, you're paid at the going wholesale rate, which hovers at $.02 - $.03 per kWh. It will be interesting to see what your utility pays for excess at True-Up.

If you consider that lifetime production costs for residential solar is usually somewhere between $.05 and $.10 per kWh, being paid wholesale is a losing proposition. Installing a too-large system has a negative ROI, and is yet another disincentive to doing so.

bb0tin | 25 mai 2020

The ROI for a 'too-large' solar varies throughout the world based on many factors. Some places have export power incentives. Some places have high export prices at peak times and low export prices at non-peak times. NZ has no rebates, incentives, utility or regulations affecting what I suggest. It is a market driven system. In NZ I have a deliberately 'too-large' solar system and the ROI is not negative.

The main points are:
1) Tesla does not allow a Powerwall user to use their battery in the best financial manner even when there are no regulatory or utility reasons preventing it from happening
2) Tesla makes having a Powerwall worse for emissions than not having a Powerwall in various places

i.e. Tesla is preventing the Powerwall from being used for the most benefit to the user, grid and emissions.
n.b. If Tesla implemented what I suggest it does not result in degradation of the Powerwall. It just timeshifts the use.

GoneSailing | 26 mai 2020

It would be great if Power Wall could charge up at night during low priced TOU rates to a level that is slightly less than what excess is during solar generation the next day. It seems that PW should be able to arbitrage the Time of Use rates, so long as the house in aggregate (power walls or solar) isn't pushing any power back into the grid. Some installs have more power wall capacity than they could fill with solar on a given day, especially if the forecast is for cloudy or rainy weather.

I could see the power companies not wanting people to sell power stored in the batteries back to the grid, but don't see any reason to not use the PW flexibility to optimize Time of Use.

azher | 28 mai 2020

As a new Powerwall 2 user in NZ, I have also been frustrated with the lack of the feature to specify when recharging from the grid can take place in an automated manner. From a consumer stand-point it seems like a minor software tweak to maximize ROI and have a beneficial environmental impact. In fact it would likely prompt me to purchase an additional Powerwall.

bb0tin | 29 mai 2020

I suspect that the lack of functionality is a deliberate choice by Tesla rather than an oversight. In various places Tesla acts as a power company by aggregating private Powerwalls and then providing them as a power source to a utility. This includes the ability to export power from the Powerwall to the grid at high demand times, which is essentially arbitraging power. /watch?v=JIWUi1dGyJQ

gregbrew | 30 mai 2020

How can Tesla "aggregate" privately owned Powerwalls? I could see this happening if Tesla retained ownership of the system, and leased roof space from the homeowner (one of the several available solar PV "ownership" models), but not if the system is not owned by Tesla.

I'd be interested to see info about a specific location where "...Tesla acts as a power company by aggregating private Powerwalls and then providing them as a power source to a utility."

bb0tin | 30 mai 2020

If you watch the video link I provided you will have your answers.

gregbrew | 31 mai 2020

Thanks for the clarification. I'm hoping that this experimental program gets rolled out to other locations besides the four in the Northeast. I'd sign up in a heartbeat.

contact | 1 juin 2020

There is a similar scheme in the UK with the 'Octopus' utility provider called the 'Tesla Tariff', but as well as a Powerwall you need to own a Tesla EV (I can't afford a Tesla with wheels) this will probably evolve into a full V2G/H2G system in the near future if it isn't already.

So I have 'hacked' my Zappi EV charger so it 'Boost Charges' when the variable tariff I am on drops below the rate I get paid for exporting my excess solar (the rates can change every 30 minutes) -

The only problem is that when the system activates it takes energy from my Powerwall (that I have filled with solar from my roof), rather than from the grid, where (at that time) it costs less to buy than the rate I get paid for exporting excess solar to the grid.

I can prevent this by manually switching my Powerwall to 'Back-Up Only' using the app, but I would really like to be able to do this automatically when the rate I am paying per kWh drops below my fixed export rate, as the lower prices often occur early in the morning, while I'm asleep.

If this could be done, there is a small added bonus in that if the Powerwall isn't fully charged when it switches over to 'Back-Up Only' it will charge to 100% at the cheaper rate.

Being able to export from the Powerwall during peak demand periods would be nice, but in the summer I'm still creating excess solar through the peak periods and my house needs about half of my Powerwalls capacity to run till sun up the next day. In the winter I'm going to need everything that is in the Powerwall to run the house plus some from the grid, so no spare capacity then to sell then.

Maybe an electro-mechanical solution like my Zappi Charger 'hack' could be wired into the gateway to locally do the switching and bypass the app/web based control?