When we added the Tesla charger to our solar system with two Powerwall II’s, we got two different recommendation from two different electrical contractors. One said to leave the charger outside the ”Tesla loop” (PowerWalls, Gateway, panels, inverter) while the other said put it inside but add a shunt to the charger circuit that would detect when power was out and stop charging the Tesla so as to avoid draining the Powerwalls during a power outage when they arguably are the most needed.
Unfortunately, the contractor informed us that they changed their mind and came up with the brilliant solution to install the charger outside the loop. We now have no way of monitoring (with Tesla app) real-time charge draw. We fake it by waiting until PowerWalls are fully charged before charging Tesla, but that doesn’t work all the time—for eg, cloudy day or day when we’re using the car at those perfect times. And it means we do all the observation/calc work.
Out local Tesla genius has informed me that there is a requested app feature called “Driving on Sunshine” and that we should all write to Tesla requesting that this feature be added. Then we would switch our charging circuits back inside the Tesla loop and the app would see the charger as a new load center and monitor all other elements, hopefully with some user adjusted preferences like Storm Watch and Battery Reserve, to let the algorithm do the observation for us. Fir those of you who are already there, it would solve that problem.
Currently, I guesstimate the timing based on cloud cover and use the onboard feature to set time if charging. For example, on a sunny summer day, our PowerWalls will usually too off by 11:30am so I set the Tesla to charge after noon. On a cloudy summer day, it’s around 2 pm instead. But it would be nice to not have to think about it each day and have the app which is pretty darn good handle this function too.
Our challenge here is that unlike our LA DWP, on Maui the power company does not buy back excess power that you generate at the same rate for which they sell it to you. Actually, in LA which switched to optional TOU meter and we get paid more fir the power we generate than fir the power we buy. In Maui, It’s either zero, or about half what you pay. So in LA, they charge more to use power during peak loads midday, which is great for home solar because they pay you highest for excess power when you’re generating the most and charge you the lowest when you’re using in the non demand night hours. . In Maui, they claim that the most power is used at night, and therefore charge you the most when we’re using our chargers and all other appliances except AC (we actually have no AC) and pay you the least when we’re generating power.
In the meantime, everyone please write to your Tesla rep requesting that the Drive on Sunshine function be added to the app. For most of us, this would complete Musk’s vision of the most efficient use of solar power to EV power, and not cause us (in Maui) to burn diesel to generate power for our wonderful EV’s when we’ve also invested in both solar and PowerWalls to do our part!
Elon MuskVerified account @elonmusk
