Posted from TOCNYS... An EV, Solar, & National Grid VTOU
For anyone in NYState under National Grid. If you have VTOU service, the day is split into two rate periods most of the year - On Peak: 7am-11pm, and Off Peak: 11pm-7am. During June-September a third rate period is added - Super Peak: 2pm-7pm. Power credits generated during these three rate periods can't be mixed, so even if you have On Peak credit, it can't be used to offset electrical usage during Off Peak times, and vice-versa. Where a problem comes in is if your Anniversary month is, say, March, and you end September with Super Peak credits, all they can do is sit there until your anniversary (or until June's Super Peak rate period starts again.) With National Grid you only have two options for your Anniversary - True-up on your Anniversary (#3 if your Month is March), or No True-up (#0 which will roll-over your electrical credits in each rate period continuously, forever.) Most people start with a yearly True-up. National Grid allows a change ONLY ONCE, so if you switch, there's no going back. If you stay with the yearly True-up, National Grid combines all electrical credit on your anniversary date (from all the rate periods) and credits your account an amount of $$ based on the wholesale On Peak rate that day. (I got roughly 5 cents/kWh for 2,000kWhs even though I'd generated almost half that during Super Peak times where the wholesale rates were 10 cents & higher) Remember that this is under VTOU Service only. I'm not sure exactly how this works if you're running solar on their SC1 standard Residential Service.
I originally set my Model 3 to start charging at 1am before I had Solar. That was the cheapest time to charge (VTOU). Then I got Tesla Solar installed, and realized that while I was gaining credit during the day, I was still being charged at night for charging. That was my WTF moment of clarity. The EV would drain the Powerwalls to the reserve setting at night and then the EV would draw from the Grid, costing me $$. Well, I decided to set the EV to start charging at 2pm. Why? Because the power walls would normally be fully recharged by then, and during the Summer 2pm starts Super Peak, who's credits can only be used from June-September, and any left at the end of September will only be trued-up at the lower On Peak rate - so why not use what you'll eventually lose? During charging I vary the power to stay below what the Solar produces, so my Powerwalls stay at 100% to bridge the sundown to sunup period and I don't draw from the Grid before the Sun starts producing again. That's my story & I'm sticking to it!