Smart Electric Water Heater Controller - Case Study
The client required a smart electric water heater controller engineered to expand their existing smart home ecosystem and address specific consumer demands for remote and off-grid residential properties. The core objective was to elevate the water heating experience in environments completely lacking access to traditional gas networks or centralized heating infrastructure—such as luxury glamping sites and remote holiday cabins. Utilizing advanced technology like the ESP32 microcontroller and WiFi Mesh integration allows these smart electric water heaters to operate efficiently in such settings.
Rather than relying on inefficient, manually operated legacy water heaters, this modern solution enables users to seamlessly program, schedule. Manage their hot water supply either via a centralized local hub or a dedicated mobile application. By delivering precise, user-defined temperature regulation, the controller maximizes user comfort while significantly optimizing energy consumption and lowering electricity expenditure.
Project Context
The smart water heater controller was engineered as a standalone edge device combining industrial power architecture with precise thermal telemetry. A primary hardware requirement was the implementation of a highly efficient, custom internal power supply capable of stepping down 230VAC mains voltage. This was achieved through a Flyback topology utilizing a TNY284 off-line switcher, a two-winding high-frequency transformer. A low-dropout (LDO) linear regulator to cleanly power the central ESP32 microcontroller.
To safely actuate the high-current heating elements, the hardware incorporates a transistor-driven 10A relay supporting both standard and bistable NC/NO configurations. Accurate, real-time thermal feedback is continuously captured via an external, cable-mounted sensor (such as the ENS210 or AHT20) communicating over an isolated I2C bus, allowing the electronics to remain protected while the probe undergoes direct thermal coupling with the water supply.
From a software perspective, the architecture was designed to prioritize autonomous reliability. The device utilizes the native ESP32 Wi-Fi Mesh protocol to act as a resilient communication node within the wider appliance network. Concurrently, it runs a localized 24-hour scheduling engine directly at the edge, ensuring that precise temperature thresholds and user routines are strictly maintained even during complete network or cloud outages.
Project Context
The smart water heater controller was engineered as a standalone edge device combining industrial power architecture with precise thermal telemetry. A primary hardware requirement was the implementation of a highly efficient, custom internal power supply capable of stepping down 230VAC mains voltage. This was achieved through a Flyback topology utilizing a TNY284 off-line switcher, a two-winding high-frequency transformer. A low-dropout (LDO) linear regulator to cleanly power the central ESP32 microcontroller.
To safely actuate the high-current heating elements, the hardware incorporates a transistor-driven 10A relay supporting both standard and bistable NC/NO configurations. Accurate, real-time thermal feedback is continuously captured via an external, cable-mounted sensor (such as the ENS210 or AHT20) communicating over an isolated I2C bus, allowing the electronics to remain protected while the probe undergoes direct thermal coupling with the water supply.
From a software perspective, the architecture was designed to prioritize autonomous reliability. The device utilizes the native ESP32 Wi-Fi Mesh protocol to act as a resilient communication node within the wider appliance network. Concurrently, it runs a localized 24-hour scheduling engine directly at the edge, ensuring that precise temperature thresholds and user routines are strictly maintained even during complete network or cloud outages.
Hardware Stack
Firmware Stack
Smart Electric Water Heater Time Estimates
The following table outlines the estimated development hours across each project milestone, from initial analysis through to physical validation of the hardware platform.
| Stage | Min h | Max h | |
|---|---|---|---|
|
Component selection |
16 |
22 |
|
|
Schematic drawing |
18 |
24 |
|
|
Component package drawing |
8 |
12 |
|
|
PCB routing |
24 |
30 |
|
|
Production files & component ordering |
10 |
14 |
|
|
Assembly & Hardware Testing |
28 |
34 |
|
|
Total Hardware time |
104 |
136 |
|
|
ESP32 WiFi Mesh communication (Node mesh integration) |
48 |
72 |
|
|
Cloud MQTT broker communication (done within the Gateway project) |
32 |
48 |
|
|
Measure water temperature |
24 |
56 |
|
|
Mobile App communication via MQTT broker |
224 |
256 |
|
|
Bussiness logic – Schedules |
104 |
136 |
|
|
Total Firmware time |
472 |
628 |
|
|
Quality Assurance |
54 |
68 |
|
|
Project Management |
54 |
68 |
|
|
Total project time |
717 |
952 |
Note: To the final total project estimated time might be added up to 15% of time for risk assessment.
