I think you're mixing up the issue a bit. PG&E will allow a residential grid-tied Powerwall to charge from the grid only if:
1) Solar or other similar generation equipment is not part of the system
2) Emergency events (like a Stormwatch)
Otherwise, your Powerwalls should only be charged with the self generation equipment.
And, my understanding is at this time, PG&E will not allow a homeowner to export stored energy to the grid under any circumstance. There's an initiative to allow residential ESS to discharge to the grid if CAISO determines a possible energy shortfall, but that'll take years to roll out if ever.
PG&E may seem like they're supportive of what you want to do; but they're the ones that definitely do not homeowners being able to charge via grid or solar as a self-initiated decision. The PoCo doesn't want people to charge batteries when TOU rates are favorable to the customer, and then not use grid energy when TOU rates go up later in the day after sunset.
Also, homeowners with solar could see in the forecast that the next few days will be cloudy. So they could bank as much as possible beforehand and totally miss a day where the PoCo would rake in cash when the homeowner used a lot of grid energy due to lack of solar production.
The PoCo's simply don't want homeowners to have the freedom to do this type of arbitrage and planning. I don't think Tesla directly cares what you do. But Tesla knows they need the PoCo's on board or else their product wouldn't be approved for use with existing infrastructure.
who wants to export stored energy to the grid? I sure do not.
I guess I just read things differently
I worked with your sales person to put in for batteries under the SGIP ER program. Below are the requirements I could find in
the SGIP 2020 handbook V9
Section 5.2 Energy storage projects may be stand-alone or paired with generating systems and must be capable of
discharging fully at least once per day.
Residential energy storage projects,
whether stand-alone or paired, must comply with additional requirements specified in the Residential
Energy Storage Eligibility Affidavit designed to ensure that all residential energy storage systems
participating in the SGIP will be used for more than just back-up emergency purposes.
Section 5.2.5 Residential systems are required to discharge a minimum of 52 full discharges per year. A “full discharge”
is the equivalent of discharging the SGIP-incentivized energy capacity, whether it is during a single or
multiple discharges.57
57 Each discharge does not have to be a 100% depth of discharge, but the aggregate amount of discharges over the year must equate
to 104 full discharges. (residential is 52)
5.2.6
Paired with On-site Renewables
To be considered paired with and charging from on-site renewables, energy storage systems must either
be claiming the Investment Tax Credit (ITC) or, if not claiming the ITC, charge a minimum of 75% from the
on-site renewable generator.
So in summary from the SGIP handbook, it states the batteries can be charged from both the grid and solar. So nothing we need to ask SGIP
since I found all we need to know in their handbook. (Too bad they did not say all batteries have to be on one gateway ☹ )
SGIP then approved me for the batteries
Second piece of data is what does PG&E want and allow. This webpage from them makes it real clear
Battery storage for your home
Key points
Potentially reduce your energy costs: If you are on a PG&E Time-of-Use rate or Home Charging rate, your battery can charge when electricity is cheaper and discharge for use in your home when electricity from the grid is more expensive.
Home battery storage systems are typically connected to both the grid and your home’s electric panel to perform two main functions:
- Charging: you can store power generated by your home rooftop solar system — or from the grid when electricity prices are lower — to be used at a later time. If an outage is imminent due to a storm or shut off event, some storage providers are able to send a signal to your battery to fully charge before the outage, in preparation to provide backup power.
- Discharging: you can use the energy stored by your battery to power your home when the price of electricity from the grid is more expensive, at night when your solar system isn’t producing (if you have solar), or during an outage when you need backup power.
Please note: You do not need a home solar system to benefit from battery storage. A battery storage system can charge solely from PG&E’s grid to be used for backup power and to shift your use of grid energy to lower-price times of day. Pairing solar with your battery, however, can provide additional benefits, such as longer-lasting backup power and increased bill savings.
So from the direct PG&E site, as shown above, PG&E actively supports charging batteries from the grid when prices are low in the TOU rate, and then use the batteries when the TOU rate is high. Pretty black and white.
