v2.8.0 - Grid Voltage Upgrade

What's Changed

• Now using ISLAND_VLxN_Main data for Grid voltage (instead of METER_x_VLxN) as this appears to be more common across systems. Upgrade script executes a run-once query to copy historic data over. #167
• Added logic to Voltage panel to sum Powerwall L1 and L2 voltages for 230V grid users thanks to @longzheng in #165
• Change frequency panel to 3 decimal places by @longzheng in #163
• Update README.md by @BJReplay in #168

New Contributors

• @longzheng made their first contribution in #163

Full Changelog: v2.7.1...v2.8.0