Using HomeWizard P1 net export to run a 750 W heater without rapid switching

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1

I tested a small surplus-power automation last winter and ran into a problem that may be familiar to anyone switching a load from live P1 data.

My setup was:

  • HomeWizard Wi-Fi P1 Meter (HWE-P1)
  • HomeWizard Energy Socket (HWE-SKT)
  • Home Assistant
  • a basic electric heater fixed at 750 W
  • gas heating as the main heat source

I used the P1 meter’s current net power as the input. The heater could start when the house exported enough power to cover the 750 W load. The Energy Socket let me confirm the heater’s consumption and switch it from Home Assistant.

The first version reacted too closely to the live power value. A short cloud or another appliance could remove the surplus within seconds. The heater then switched off and came back on when the value crossed the threshold again.

I later added a weather forecast condition. The automation checked both the current surplus and whether the sunny period looked likely to continue. That reduced the rapid switching in this setup. I did not keep the exact thresholds, entity names or weather provider, so I cannot share reliable drop-in YAML.

The useful part for me was the order of work:

  1. Check how the P1 integration reports import and export in your own setup.
  2. Measure the appliance by itself and confirm its real power draw.
  3. Observe how fast the net value moves when clouds and household loads change.
  4. Add a second condition before letting the automation switch the load.
  5. Keep manual control and a safe off state.

An electric heater needs extra care. I kept the load at 750 W. The socket’s maximum rating does not prove that a heater, wall outlet or remote switching arrangement is safe. The heater manual and local electrical guidance still apply, including any requirements for a thermostat, overheat protection and external switching.

I saw lower gas use while running this setup, but I did not run a controlled before-and-after measurement. I cannot attach a percentage or cost saving to it.

I would be interested in how others stop short changes in net export from causing repeated switching. Do you use a start/stop margin, a minimum run time, a forecast condition, or a combination?

2

It’s really hard. You could use a threshold? Like for example if it is above or below 750 W for 2 minutes.

My P1 meter shows accurately when a cloud is before the sun, then solar power could drop significantly.

I use an infrared heating panel in one room. I only use it in the winter and when there is presence in the room.

3

Hello,
You may want to look towards a solution with different switching element - a dimmer with PID control.
That would eliminate rapid switching and improve electrical safety situation (if properly implemented).
Solar diverter or solar tracker are key words you may be interested in while looking online.