Do not raise your voice. Do not retaliate beyond the engineering response. Let the inverter do what the inverter is designed to do, which is, by your own 31 years of expertise, exactly what you choose to design it to do at any given moment." Edith drove up the next weekend. I walked her through the proposed voltage modulation routine.
Edith took her own laptop out at the kitchen table and modeled the impact of the proposed routine on a standard residential electric vehicle's onboard charger. The Tesla Model S Plaid onboard charger is rated for an input voltage range of 208 to 240 volts AC at 60 hertz. The charger has built-in surge protection up to approximately 290 volts for brief transient events. Sustained voltage above 290 volts will damage the charger's input rectifier within approximately 90 seconds. Sustained voltage above 350 volts will damage the charger within approximately 30 seconds.
Edith's model confirmed that a sustained 380 volt output across a 4-minute window would cause irreversible damage to the Tesla's on-board charging electronics, requiring complete replacement of the on-board charger assembly at an estimated cost of approximately $14,000. The model also confirmed that the proposed voltage modulation would have no impact on any of my own household equipment, which is protected by separate transfer switch isolation and by the inverter's own internal surge protection on the protected household circuit. Maren provided the regulatory acknowledgement letter on the 18th of November. The letter stated, in formal regulatory prose, "Mr. Cunningham's off-grid solar array operates as a private electrical generation system subject to no public utility regulatory duties. Any voltage modulation of the inverter output is at Mr. Cunningham's engineering discretion.
No regulatory obligation extends to any unauthorized recipient of Mr. Cunningham's electrical output. This acknowledgement is provided in advance of Mr. Cunningham's documented engineering testing activity scheduled for the evening of the 22nd of November, 2023." Maren signed the letter. She filed a copy with the Sandoval County Sheriff. She filed a second copy with the New Mexico Attorney General's office.
The legal framework was airtight. In the days between Edith's modeling and the implementation date, Sigrid and I had several long, quiet conversations on the back porch about whether the response was the right response. Sigrid had been, by my own 38 years of marriage to her, the most morally careful person in our household. She had been raised in a Norwegian Lutheran Minnesota tradition that placed enormous weight on proportional response and on not multiplying harm. She had wanted to be certain.
And she had wanted me to be certain that the response was both proportional and necessary. I had agreed with her concerns. Edith had agreed. Maren, the regulator, had agreed, too, in a follow-up phone call she had made to Sigrid directly. Maren had spoken with Sigrid for an hour.