u/matthewhe22

I wanted to share a system I've been running that automatically charges my Tesla using only solar + battery surplus — zero grid import.


How it works:
- Every 2 minutes, it reads solar generation, battery SOC, and household load
- Formula: Available Power = Solar Gen + Battery Discharge(max 5kW) − Household Non-EV Load
- If available < 200W → pauses. Otherwise sets charge current 5-32A
- Integrates Alpha ESS (solar/battery) + Tesla Wall Connector via Home Assistant


Real example from my setup:
☀ 2,525W solar + 🔋 5,000W battery − 🏠 312W house = ⚡ 7,213W → 16A charging at $0 grid cost


It saves around $300+/year vs peak-rate charging and requires zero touch — set it once and it just works.


Full details here if anyone's curious:
capconnex.com.au/tesla-auto-charging/


Happy to answer questions!