A power audit measures the electricity consumption of every device in your home, identifying energy waste and optimisation opportunities. In Indian households paying ₹5-10 per kWh, a thorough power audit typically reveals 15-30% savings potential — translating to ₹500-2,000 monthly savings. This guide covers measurement tools, systematic auditing methods, and building a DIY power logger for continuous monitoring.
What Is a Home Power Audit?
A power audit catalogues every electrical device in your home, measures its actual power consumption, calculates daily and monthly usage, and identifies the biggest energy consumers. Many devices consume far more (or less) than their labels suggest, and standby power from devices you think are “off” can account for 5-15% of your electricity bill.
Tools Needed for a Power Audit
- Kill-A-Watt meter (or equivalent): Plug-in power meter that shows watts, VA, kWh, and power factor. Available on Amazon India for ₹800-2,000.
- Clamp meter: For measuring current on individual circuits at the distribution board without disconnecting wires. ₹500-2,000.
- Watt meter (inline): For 12V/DC measurements on solar systems and battery loads.
- Spreadsheet: To record all measurements and calculate costs.
Measuring Individual Device Power
Systematic approach for an Indian home:
Category 1: Always-on devices (measure 24h consumption)
WiFi router: 8-15W → 192-360Wh/day
DTH set-top box (standby): 10-20W → 240-480Wh/day (!)
Phone charger (idle): 0.5-2W → 12-48Wh/day
Refrigerator: 30-80W average → 720-1920Wh/day
Category 2: Scheduled devices
Ceiling fan: 50-75W x 12h = 600-900Wh/day
LED tube light: 18-22W x 6h = 108-132Wh/day
Geyser: 1500-3000W x 0.5h = 750-1500Wh/day (!)
Washing machine: 400-500W x 1h = 400-500Wh/week
Iron: 1000-2000W x 0.25h = 250-500Wh/use
Category 3: Occasional high-power
AC (1.5 ton): 1000-1800W x 8h = 8000-14400Wh/day (!!)
Microwave: 900-1200W x 0.1h = 90-120Wh/useBuilding an Arduino Power Logger
// Whole-house power logger using SCT-013 + ZMPT101B
// Logs to SD card for monthly analysis
#include <EmonLib.h> // Open Energy Monitor library
EnergyMonitor emon;
void setup() {
emon.voltage(A0, 234.26, 1.7); // ZMPT101B calibration
emon.current(A1, 30.0); // SCT-013-030 calibration
}
void loop() {
emon.calcVI(20, 2000); // 20 half-wavelengths, 2s timeout
float Vrms = emon.Vrms;
float Irms = emon.Irms;
float realPower = emon.realPower;
float apparentPower = emon.apparentPower;
float pf = emon.powerFactor;
// Log to SD card with timestamp
// Calculate kWh accumulation
delay(5000); // Log every 5 seconds
}Analysing Your Energy Data
After a week of data collection, create a pie chart of energy consumption by device category. Common findings in Indian homes:
- Air conditioning: 40-60% of summer bill
- Refrigerator: 15-25% of base bill
- Water heating: 10-15%
- Lighting: 5-10% (more if still using CFL/incandescent)
- Phantom loads: 5-15% (standby power from TVs, set-top boxes, chargers)
Quick wins for Indian homes:
- Switch DTH box to power strip with switch: save ₹50-150/month
- Set AC to 26degC (BEE recommendation): save 15-20% on AC bill
- Replace CFL with LED: 50-60% lighting savings
- Use timer on geyser: save ₹200-500/month in winter
FAQ
How accurate are plug-in watt meters from Amazon India?
Most ₹800-1,500 watt meters achieve 2-5% accuracy — sufficient for a home audit. For best results, verify the meter reads zero watts with no load connected (some cheap meters show 1-3W phantom reading). The energy (kWh) reading over 24 hours is more accurate than instantaneous watts.
Can I use my solar inverter’s monitoring to audit?
Partially. Solar inverters track total generation and consumption but not per-device breakdown. For a proper audit, you need per-device measurement. However, the inverter’s daily production and consumption graphs help identify peak usage times and baseline loads.
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