The PV Hot Water Control System helps you reduce electricity bills by ensuring that your electric water boiler (hot water system) is primarily powered by solar energy. This increases the self-consumption rate of your PV system and minimizes your grid electricity usage.
This system is commonly implemented using the WEM3050T Wi-Fi energy meter and the WPC3700 Wi-Fi power controller from IAMMETER.
🎬 Video Demo: WPC3700 Working with WEM3050T
This solution is ideal for homeowners whose systems meet the following conditions:
The system is built with the Energy Cost Reduction Kit, which includes:
How it works:
This ensures your hot water system uses solar energy first, maximizing your PV investment and reducing electricity bills.
Both the WEM3050T energy meter and WPC3700 power controller support open communication protocols such as MQTT and Modbus/TCP, making them ideal for integration into open-source home automation platforms like Home Assistant (HA) and Node-RED.
With this setup, you can easily create an automation rule that dynamically adjusts the power output of your hot water boiler based on real-time solar surplus data:
This open integration makes the PV Boiler Control System highly flexible — it can work standalone, or be fully automated and customized through your preferred smart home platform.
Learn more: Enable MQTT Discovery in Home Assistant (Firmware i.76.058.8)
Before vs. After deploying the PV boiler control system:
Before
After
Electricity cost mainly depends on:
- Boiler energy consumption
- The proportion of energy supplied by solar power
- The price difference between grid electricity and feed-in tariff
Example:
Suppose you have a single-phase electric boiler or hot water tank (maximum power < 3.7 kW) with a solar PV system.
💡 Daily savings = (0.25 – 0.05) × (10 × 0.5) = 1 AUD/day
Daily Usage | Solar Proportion | Feed-in Tariff | Grid Price | Daily Savings |
---|---|---|---|---|
10 kWh | 50% | 0.05 | 0.25 | (0.25 – 0.05) × (10 × 0.5) = 1 |
20 kWh | 30% | 0.05 | 0.25 | (0.25 – 0.05) × (20 × 0.7) = 2.8 |
You can estimate potential savings based on your own solar generation and boiler usage.
Depending on your setup, the WPC3700 solar boiler controller can operate in several modes:
Select the operating mode that best fits your system requirements.
This document was last updated on October 15, 2025.
Three Phase Wi-Fi Energy Meter (WEM3080T)
Single Phase Wi-Fi Energy Meter (WEM3080)
Three Phase Wi-Fi Energy Meter (WEM3046T)
Three Phase Wi-Fi Energy Meter (WEM3050T)