SunSpec

SunSpec is not a wire protocol of its own. It is a set of standard models (register maps) that distributed energy resources expose over Modbus: inverters, meters, batteries, string combiners and more. A device starts its map with the SunS marker at a base address, followed by a chain of models, each identified by a number (for example 103 for a three-phase inverter). Values carry scale factors, so a raw register becomes watts, volts or amps only after decoding.

Where you meet it

• Solar inverters and hybrid inverters
• Battery storage systems and their energy management
• Revenue and production meters on DER sites

Quickstart

From the command line

sunspecctl ships with go-sunspec. Download it from GitHub Releases, then:

# Is this a SunSpec device, and at which base address?
sunspecctl detect --url tcp://192.168.1.100:502

# Which SunSpec models does it implement?
sunspecctl models --url tcp://192.168.1.100:502

modbusctl client sunspec probe gives a quick check from the Modbus CLI too.

From Go

go get github.com/otfabric/go-sunspec

Discover the device and print the scaled points of a three-phase inverter model (abridged from the go-sunspec README):

client, _ := modbus.New(modbus.Config{URL: "tcp://192.168.1.100:502"})
if err := client.Open(); err != nil {
  log.Fatal(err)
}
defer client.Close()

device, err := sunspec.Discover(ctx, client, &sunspec.DiscoverOptions{UnitID: 1})
if err != nil {
  log.Fatal(err) // errors.Is(err, sunspec.ErrNotSunSpec) when the device is not SunSpec
}

inverter, err := device.ReadModelByID(ctx, 103) // three-phase inverter
if err != nil {
  log.Fatal(err)
}
for _, p := range inverter.Group.Points {
  if p.Implemented && p.ScaledValue != nil {
    fmt.Printf("%s = %g %s\n", p.Name, *p.ScaledValue, p.Units)
  }
}

What go-sunspec supports