AION EMS Zeus treats water heating as an important part of your home energy system.
Electric water heaters, immersion heaters and smart devices such as my-PV AC ELWA 2 can represent a significant flexible load. By connecting them to Zeus, you can monitor their energy consumption, water temperature and operating activity — and supported devices can also participate in Zeus Smart Control.
Water Heating remains separate from Heat Pump DHW production, allowing Zeus to understand which device is actually using energy to heat your domestic hot water.
Before You Start
Your water-heating device should already be connected to Home Assistant through its normal integration.
Depending on the device, Home Assistant may provide:
- Current electrical power
- Accumulated electrical energy
- Water / boiler temperature
- Heating-element temperature
- Operating state
- Controllable power
- Switch or actuator entities
You do not need all of these measurements for basic monitoring.
Step 1 — Add the Water Heater
Open:
AION EMS Zeus → Device Manager → Add Device
Choose:
DHW / Water Heater
Give the device a clear name, for example:
Water Heater
Boiler Heater
ELWA
AC ELWA 2
Zeus will treat this as an independent water-heating device.
Step 2 — Connect Electrical Power
Select the Home Assistant entity representing the device’s current electrical power consumption.
This should normally be measured in:
W or kW
For example:
Power: 1,250 W
This allows Zeus to show when the Water Heater is active and how much electricity it is currently consuming.
For controllable devices, this measurement also provides important feedback that Zeus can use to verify actual device behavior.
Step 3 — Connect Electrical Energy
If available, select the accumulated energy sensor for the Water Heater.
This will normally use:
Wh or kWh
and commonly reports:
device_class: energy
state_class: total_increasing
This allows Zeus to include Water Heating in historical energy statistics and device consumption analysis.
Do not use a W/kW Power sensor in an Energy field expecting Wh/kWh.
Step 4 — Connect Water Temperature
Select the Home Assistant entity representing the current Domestic Hot Water / boiler temperature.
This should normally be measured in:
°C
For example:
DHW Temperature: 61.5 °C
Temperature information helps Zeus understand the current state of the hot-water system and becomes especially important when Smart Control is enabled.
Heat Pump DHW and Water Heating Are Different
If your Heat Pump also produces domestic hot water, you may already have configured a DHW section inside the Heat Pump.
That does not replace the Water Heater device.
For example, an installation may contain:
Heat Pump → DHW
and separately:
my-PV AC ELWA 2 → Water Heater
Both devices may heat the same hot-water tank, but they consume energy independently.
Zeus therefore keeps them separate.
This allows the system to distinguish:
Heat Pump DHW consumption & generation
from
additional electric Water Heater consumption
without double counting the two devices.
my-PV AC ELWA 2
Zeus has been real-world validated with the my-PV AC ELWA 2.
For basic monitoring, configure the normal Water Heater measurements:
Power
Energy
DHW / Boiler Temperature
If your installation also exposes the ELWA heating-element temperature, it can later be used as additional safety evidence for Smart Control.
Step 5 — Save and Verify
Click:
Add Device or Update Device
Then open the Command Center.
When the Water Heater is operating, its power should approximately match the corresponding Home Assistant entity.
For example:
Home Assistant ELWA: 1,200 W
Zeus Water Heater: approximately 1,200 W
The Water Heater block should also show the configured DHW temperature when available.
Step 6 — Check Device Activity
Once the Water Heater has a valid Power measurement, Zeus can identify when it starts and stops heating.
This activity can be used throughout Zeus for:
Device Analytics
Energy Statistics
Home Energy Timeline
Known Load Accounting
When the Water Heater starts, the increase in household consumption should correspond with its measured power.
Smart Control — Optional
Monitoring and controlling a Water Heater are two different things.
By default, a newly registered Water Heater can remain:
Observe Only
In this mode, Zeus monitors the device but does not control it.
If you want Zeus to control a supported device such as the my-PV AC ELWA 2, configure it later under:
Smart Control & Safety
Control must be explicitly enabled by the user.
Zeus does not automatically take control of a registered Water Heater.
ELWA Smart Control Requirements
For advanced ELWA control, Zeus can use additional information such as:
Available solar surplus
Grid import/export
Boiler temperature
Heating-element temperature
Current ELWA power
Configured minimum and maximum power
The exact control configuration belongs in the Smart Control section of this guide.
The important point during Water Heater setup is to make sure the basic measurements are correct first.
Safety First
Before enabling Smart Control, verify that:
- Power values match Home Assistant.
- DHW temperature is correct.
- Heating-element temperature is correct if configured.
- The device behaves normally under its original manufacturer controls.
- Zeus remains Observe Only until you deliberately grant control permission.
Smart Control should never be used to compensate for an incorrect sensor mapping.
What If I Only Have a Power Sensor?
That’s fine.
Zeus can still monitor the Water Heater as a registered household load.
Additional measurements unlock additional capabilities:
Power only → live consumption and activity
Power + Energy → historical consumption
Power + Temperature → water-heating context
Control + safety evidence → Smart Control capability
You do not need to fill every available field.
Water Heating Connected
Once the Water Heater power and temperature match the real device, the basic configuration is complete.
If you only want monitoring, you can leave the device in Observe Only.
If you want Zeus to intelligently use solar surplus with a supported Water Heater, continue later with the Smart Control setup.
Next: Connect Your EV Charger
Know when your water is heating, how much energy it uses, and where that energy comes from.