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Load Control Based on Available Excess PV Power

What We Control?

This is a widespread case when we need to power on a controllable device when we have enough power. In our case, we want to run pool pump from solar.

Objective of Automation

Operate the pump only when there is an excess of power available. It is important to avoid running the pump if the batteries have not yet been charged - we don't want to have no power at night.


It is necessary to have at least two devices: one that can switch the power on or off for the controlled device (pump), and another device that provides information on the amount of available photovoltaic (PV) power and battery SOC (state of charge).

For this recipe, we will use a hybrid solar inverter that provides two telemetry parameters:

  1. total_pv_input_power - this refers to the total amount of power that is being produced by the solar panels now.
  2. battery_capacity - this parameter indicates the state of charge of the battery.

A water pump which is powered via a Sonoff 4 channel smart relay and is connected to the second relay channel.


-- define devices by using UCM ID
local inverter = enapter.device('A21D1F00E16CB9A75BAE11EB16D001E7')
local switch = enapter.device('B9B9B8D86D10C0B24C0EB40C1E903F99')

-- define controller (state machine) with default no_pv_power state
local ctrl = controller('load_control', { initial = 'no_pv_power' })

-- methods names must begin with run_ prefix
function ctrl:run_no_pv_power()
-- in order to avoid flapping of the pump when power
-- disappear / appear, we put set grace period of 15 min
if self:time_in_state() > 15*60 then
-- when we have more than 2000W of available PV power and
-- battery charged 85% we go to next state - available_pv_power
if'total_pv_input_power') > 2000
and'battery_capacity') > 85 then

-- switch count starts from 0. when swith On we execute command switch_off_1
if'switch1') == 'On' then

function ctrl:run_available_pv_power()
-- grace period is good practice, don't underestimate it.
if self:time_in_state() > 15*60 then
-- when we have less or equal to 2000W of available PV power or battery charged
-- less or equal than 85% we go to next state - no_pv_power
if'total_pv_input_power') <= 2000
or'battery_capacity') <= 85 then

-- switch count starts from 0. when swith Off we execute command switch_off_1
if'switch1') == 'Off' then

-- start state machine
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