Time-of-Use Tariff in Thailand
MEA (Bangkok, Nonthaburi, Samut Prakan) and PEA (provincial areas) offer TOU tariff structures for customers who apply for a TOU meter: Peak Hours: 09:00–22:00 on working days at ~5.0–6.0 THB/unit. Off-Peak Hours: 22:00–09:00 and holidays at ~2.5–3.0 THB/unit.
The price difference is ~2–3 THB/unit. Shifting washing machines, dryers, and dishwashers (combined ~1,000–1,500 units/year) to off-peak saves 2,000–4,500 THB/year.
Smart Plug Ecosystem for TOU Scheduling
TP-Link Kasa EP25/EP235: smart plug supporting energy monitoring up to 15A, integrates with Home Assistant via local API (no cloud dependency). Schedule automations by time.
Sonoff S26R2: 16A smart plug at low cost; flash with Tasmota and connect directly to Home Assistant via MQTT with no cloud dependency.
Shelly Plug S Plus: 2,500W/16A energy monitor with ±1% accuracy — the best choice for precise power consumption monitoring.
Appliance Scheduling Table
Washing Machine (500–800W): schedule spin cycle to start at 23:00 and finish before 06:00. Use the machine’s built-in delay start, or a smart plug to cut power after a set duration for older models without timers.
Dryer (1,500–3,000W): the highest wattage appliance in the home. Never allow it to run during peak hours. Home Assistant monitors: if Watt > 500W during peak, turn off and send a LINE alert immediately.
Dishwasher (1,200–2,400W): schedule after midnight; 60–90 minute cycle completes before waking.
Storage Water Heater (2,000–4,000W): heat water from 04:00–06:00 off-peak, then shut off the heater during peak. Insulation maintains temperature for 2–4 hours.
Refrigerator (100–200W continuous): do not cut power, but use a smart plug to monitor wattage for compressor faults (abnormal watt draws).
Rice Cooker Optimization
IH (induction heating) rice cookers draw 1,200–1,500W during the heating phase but for a short duration. Schedule cooking during off-peak so rice is ready exactly at wake-up or dinner time. Smart plugs with Home Assistant deliver precise scheduling.
Home Assistant Automation Logic
At 22:00: turn on washing machine plug, turn on dishwasher plug, send LINE message. At 09:00 on working days: if washer plug watt > 100W, turn off and send LINE alert; if dryer plug watt > 500W, turn off and send LINE alert.
ROI and Real Savings
Cost: 4–6 smart plugs × 500–800 THB = 2,000–4,800 THB. TOU meter replacement: free (MEA charges nothing for the switch). Annual savings: 3,000–6,000 THB for households using 500–800 units/month. ROI: 4–18 months depending on usage patterns.