Your site and the solar forecast
Settings › Site holds everything about the installation. Entering your location and roof arrays switches on the solar forecast that rules, the Energy page and the AI planner all rely on.
From top to bottom, the page holds:
- the Tesla connection (see Connecting your Powerwall)
- the System facts
- your Location and PV arrays
- the Local gateway (Android app only)
- the EV charger (see EV chargers)
System
The System card shows read-only facts from Tesla: hardware, capacity, peak power, firmware, install date, time zone, and the tariff currently on the Powerwall.
Location
Enter your latitude and longitude to two or three decimal places. Forecasts work at about 1 km resolution, so the nearest street is plenty. The easiest way to find them is to long-press your house in Google Maps and copy the two numbers it shows. Coordinates are stored encrypted and shared only with the weather service, Open-Meteo.
PV arrays
Add one row per string or roof aspect, with:
- a name, such as "East roof"
- its size in kWp
- its tilt in degrees from horizontal (a typical UK pitched roof is 30–40°)
- its azimuth as a compass bearing: 0 is north, 90 is east, 180 is south and 270 is west
Your installer's paperwork has the kWp for each string. You can estimate tilt and direction from the roof itself. Press Save location and arrays when you are done.
How the forecast works
SunHarvest fetches hourly radiation forecasts for your location and runs them through each of your arrays. Several things are computed from that:
- the solar forecast
- the "still to come" figure for today
- tomorrow's outlook
- every forecast-based rule signal
Without arrays there is no PV forecast. Forecasts reach two days ahead and refresh hourly. After a week or so of metered data, SunHarvest scales the forecast by one factor learned from what your panels actually produced, so it settles on your roof's real output. Calibration starts again when you change your arrays or location.
Why forecasts matter for a battery. Whether to charge from the grid overnight depends on tomorrow's sun. A sunny day will fill the battery for free, so buying grid power at night would be wasted. A grey day means the cheap overnight slot is the best energy you will get. Rules and the AI planner use the forecast to make that call every day.
Local gateway (Powerwall 3, Android app, unofficial)
A Powerwall 3 reports each solar string (volts, amps and watts per roof), but only over your home network, not through Tesla's cloud. That is why this card is in the Android app only; the website never shows it.
Set it up at home:
- Press Enrol this phone.
- Wait for Verification, which is usually automatic.
- Enter the gateway password and press Read the strings.
From then on, the app reads the strings while it is open at home, and Home shows them on the web too. While the app is open at home, Home's battery and power flows also come straight from the Powerwall every few seconds instead of every half minute from Tesla's cloud; the footer then says "live from your Powerwall". Give each PV array its Gateway inputs and the string tiles on Home carry the array's name. Tesla does not document this interface, so a Powerwall update may break it.