Smart Electricity Consumption Monitor with ESP32: Track Daily Energy Usage Automatically

Contents list

1. Introduction
2. What Is a Smart Daily Electricity Consumption Monitor?
3. How the System Works?
4. Aggregate Consumption vs. Appliance-Level Monitoring
5. Main Components of the System
6. Choosing the Electricity Sensor
7. Measuring Current with a Current Transformer
8. Measuring Power and Energy Consumption
9. ESP32 Data Acquisition and Processing
10. Wiring Diagram and Circuit Connections
11. Programming the ESP32
12. Displaying Daily Electricity Consumption
13. Daily Energy Calculation and Data Storage
14. Detecting Abnormal Electricity Consumption
15. Calibration and Measurement Accuracy
16. Electrical Safety and Installation Considerations
17. Possible Improvements and Future Expansion
18. Frequently Asked Questions
19. Conclusion

Time reading is 20min.

1. Introduction

Electricity consumption is often difficult to evaluate because the electricity meter normally provides a cumulative reading rather than showing how much energy is being used during different periods of the day.

A simple monitoring system can make this information easier to understand by continuously measuring the electricity consumption of a selected group of appliances and presenting the results on a display.

The Smart Daily Electricity Consumption Monitor with ESP32 is designed for this purpose.

The system measures the combined electrical consumption of the appliances connected to a particular circuit or area, processes the measurements using an ESP32, and displays useful information such as current power and accumulated daily energy consumption.

The important point is that this project is intended for aggregate consumption monitoring.

It does not attempt to determine exactly how much electricity each individual appliance consumes. Instead, it answers a simpler and often more useful question:

How much electricity did this group of appliances consume today, and is that consumption within the expected range?

For example, if a group of appliances normally consumes approximately 8 kWh during a typical day but the monitor records 13 kWh, the user has an indication that something unusual happened. The user can then review which appliances were operating during that day and investigate the reason for the higher consumption.

This approach makes the project suitable for hobbyists and beginners while still providing an interesting practical application for engineers interested in embedded systems, electrical measurement, data processing, and energy monitoring.

2. What Is a Smart Daily Electricity Consumption Monitor?

A smart daily electricity consumption monitor is an electronic system that measures the electrical energy used by a particular circuit or group of appliances over time.

The system typically contains four basic stages:  Sensor → ESP32 → Data Processing → Display

The sensor detects an electrical parameter associated with the load, such as current.

The ESP32 receives the sensor signal, converts it into digital data, performs the required calculations, and keeps track of the accumulated energy consumption.

The display can then show information such as:

• Instantaneous power
• Current consumption
• Energy consumed today
• Energy consumed during previous days
• Daily consumption history
• High-consumption warnings

The ESP32 is particularly useful for this type of project because it combines a microcontroller with communication capabilities and analog interfaces. The ESP32 family includes ADC peripherals that can be used to digitize analog sensor signals.

The project can therefore be expanded beyond a simple display into a small energy-monitoring platform capable of recording and analyzing consumption patterns.

3. How the System Works?

The basic operating principle is straightforward.

A sensor is installed on the electrical conductor supplying the appliances that need to be monitored.

The sensor produces a signal related to the electrical current flowing through that conductor.

The ESP32 samples this signal and processes the measurements.

The software can then calculate or estimate electrical power and accumulate the energy consumed over time.

A simplified signal path looks like this:

Electrical Load → Current Sensor → Signal Conditioning → ESP32 ADC → Calculations → Display

For a more advanced system, the measurement path can include both voltage and current:

AC Supply → Voltage Sensor + Current Sensor → ESP32 → Real Power Calculation → Energy Accumulation → Display

The energy value is normally expressed in kilowatt-hours (kWh).

For example, if a load consumes approximately 1 kW continuously for two hours, its energy consumption is approximately:

Energy = Power × Time

Energy = 1 kW × 2 h = 2 kWh

In a real household or workshop, power changes continuously because appliances switch on and off. The ESP32 therefore needs to repeatedly sample the electrical signal and accumulate the energy over time rather than simply taking one measurement.

4. Aggregate Consumption vs. Appliance-Level Monitoring

This distinction is fundamental to the project.

The proposed system measures the combined consumption of the appliances connected to the monitored circuit.

  Suppose the monitored circuit contains:

• Refrigerator
• Television
• Computer
• Lighting
• Fans

If all of these loads are supplied through the monitored conductor, the sensor sees their combined current.

The system therefore measures:  Total Consumption = Refrigerator + Television + Computer + Lighting + Fans

• It does not automatically know which portion belongs to each appliance.
• This is not a limitation of the project design; it is actually the intended operating principle.
• The objective is to establish a daily baseline and determine whether total consumption is normal.

For example:

The significantly higher value on Friday would provide a reason to investigate what happened that day.

The user could then consider questions such as:

• Was an air conditioner used for a longer period?
• Was a high-power appliance operating?
• Was additional equipment connected?
• Did an appliance remain switched on accidentally?
• Was the increase caused by normal activity?

This makes the monitor a daily energy-awareness and abnormal-consumption detection tool, rather than a device-level energy analyzer.

5. Main Components of the System

A practical implementation can be built from several main components.

ESP32 Development Board

• The ESP32 is the central controller.
• It receives measurement data, performs calculations, stores daily totals, and controls the display.
• The original ESP32 includes ADC hardware capable of digitizing analog signals, with two 12-bit SAR ADCs and multiple analog-capable channels.
• However, the exact ADC characteristics and available pins depend on the particular ESP32 family and board being used, so the appropriate datasheet should always be checked before designing the measurement circuit.

Current Sensor

• A current transformer (CT) is one practical option for measuring AC current without making a direct electrical connection between the sensor and the mains conductor.
• CT sensors are commonly used for whole-building and circuit-level electricity monitoring.

Signal-Conditioning Circuit

The raw sensor signal may not be suitable for direct connection to an ESP32 ADC.

Depending on the sensor type, the circuit may require components such as:

• Burden resistor
• Voltage bias
• Filtering
• Protection
• Signal scaling

The purpose is to produce an analog signal within the safe input range of the ESP32 ADC.

Display

The display provides the user interface.

Possible options include:

• OLED display
• LCD
• TFT display
• Touchscreen display

A small OLED is sufficient for a basic project, while a larger TFT display can present graphs and historical consumption data.

Real-Time Clock or Time Source

If the project needs accurate daily records, it needs a reliable way to determine the current time.

Possible approaches include:

• RTC module
• Network time synchronization using Wi-Fi
• Internal ESP32 timekeeping combined with periodic synchronization

Data Storage

For storing historical daily consumption, the project can use:

• ESP32 flash memory
• EEPROM-style storage
• microSD card
• External database
• Cloud platform

The simplest version can display today’s consumption without permanently storing historical data.

6. Choosing the Electricity Sensor

Sensor selection is one of the most important design decisions.

For AC electricity monitoring, a current transformer (CT) is a practical choice because it can measure current without requiring a direct electrical connection to the conductor being measured.

Open Energy Monitor specifically describes CT sensors as useful for monitoring whole-building electricity consumption and explains that a split-core CT can be placed around a single live or neutral conductor.

When selecting a sensor, consider:

Current Rating

The sensor should be appropriate for the maximum current expected in the monitored circuit.

Using a sensor with a suitable measurement range helps avoid excessive saturation and improves measurement resolution.

Output Type

CT sensors can have different output configurations.

Some produce a current output and require an external burden resistor, while others provide a voltage output with the burden resistor already incorporated.

The interface circuit must therefore be designed specifically for the selected sensor.

Measurement Accuracy

Sensor accuracy matters particularly when the system is expected to detect relatively small changes in daily energy consumption.

Isolation

A properly designed CT provides galvanic isolation between the primary conductor and the secondary measurement circuit.

This is an important advantage for experimental energy-monitoring systems, although isolation does not eliminate the hazards associated with working around mains wiring.

7. Measuring Current with a Current Transformer

A current transformer works according to the transformer principle.

When alternating current flows through the primary conductor, it creates a changing magnetic field.

The CT’s secondary winding produces a smaller current proportional to the primary current.

Conceptually:  I (secondary) ∝ I (primary)

The current transformer therefore converts a potentially large mains current into a much smaller measurement signal suitable for an electronic measurement circuit.

However, the CT must be installed correctly.

The sensor should normally be placed around one current-carrying conductor only.

If the CT is placed around both the live and neutral conductors of a single-phase circuit, the magnetic fields produced by the two conductors largely cancel because the currents flow in opposite directions.

Open Energy Monitor specifically warns that the CT should be installed around a single conductor rather than the complete multi-core cable.

A current-output CT also requires appropriate secondary-side circuitry.

In particular, a burden resistor is used to convert the CT secondary current into a measurable voltage.

The burden value must be selected according to the CT characteristics and measurement requirements.

8. Measuring Power and Energy Consumption

Measuring current alone is not exactly the same as measuring real electrical power.

For AC loads, real power depends on both voltage and current as well as their phase relationship.

A simplified relationship is:  P = V × I × PF

where:

• P = real power in watts
• V = RMS voltage
• I = RMS current
• PF = power factor

For purely resistive loads, the power factor can be close to 1. However, many modern appliances use electronic power supplies, motors, compressors, or other circuits that can cause the relationship between current and real power to differ.

Open Energy Monitor’s more complete energy-monitoring approach measures both voltage and current and can calculate real power, apparent power, RMS voltage, RMS current, and power factor.

Current-Only Approach

A simpler project can measure current and assume a nominal supply voltage and an estimated power factor.

This reduces hardware complexity but makes the result an approximation.

Open Energy Monitor documents this type of current-only approach and notes that it is simpler but less accurate than measuring voltage as well as current.

Voltage-and-Current Approach

For better measurement accuracy, the system can measure:

• AC voltage
• AC current
• Phase relationship

The ESP32 can then calculate real power continuously.

This is the preferable approach when the objective is to obtain measurements that can be compared more closely with an electricity meter.

From Power to Energy

Once power is known, energy can be accumulated over time.

If the measured power is represented in watts:  Energy (Wh) = Power (W) × Time (h)

For continuously changing loads, the software effectively performs repeated accumulation:  Energy ≈ Σ Power × Δt

The result can then be converted into kilowatt-hours:  Energy (kWh) = Energy (Wh) ÷ 1000

This accumulated value is the main parameter needed for the project’s daily monitoring objective.

9. ESP32 Data Acquisition and Processing

The ESP32 acts as the measurement and processing unit.

Its ADC converts the analog sensor signal into digital values that software can process. Espressif documents the ESP32 ADC as supporting both one-shot and continuous measurement modes, with calibration features available through the ESP-IDF ADC driver.

 A simplified software process is:

1. Read the sensor signal.
2. Remove the signal offset.
3. Convert the ADC value into a physical measurement.
4. Calculate RMS current or other required parameters.
5. Calculate or estimate power.
6. Accumulate energy.
7. Update the display.
8. Save the daily total when required.
9. Repeat the process continuously.

The sensor signal should generally be sampled many times rather than relying on a single ADC reading.

This is particularly important for AC measurements because the current waveform changes continuously.

Filtering

Real electrical measurements contain noise.

Software can use techniques such as:

• Averaging
• Digital filtering
• RMS calculations
• Offset removal
• Calibration coefficients

The ESP32 documentation also notes the use of multiple samples and filtering or averaging to improve ADC measurement behavior.

For a beginner project, the important concept is simple:

More carefully processed samples generally provide a more stable measurement than individual raw ADC readings.

10. Wiring Diagram and Circuit Connections

The wiring of the project can be divided into two completely different sides:

Mains measurement side → Current Transformer → Low-voltage measurement circuit → ESP32

The ESP32 should never be connected directly to the AC mains. A current transformer provides an isolated way to sense the current flowing through the monitored conductor, while the low-voltage electronics process the resulting signal.

For the example circuit in this article, the following components are assumed:

The exact burden resistor must always be selected according to the specific CT being used. Open Energy Monitor’s example for an SCT-013-000 with a 3.3 V measurement system uses an 18 Ω burden resistor.

Basic Wiring Diagram

                 AC MAINS
        ┌──────────────────────────┐
        │                          │
        │      LIVE CONDUCTOR      │
        │───────────────┐          │
        │               │          │
        │             [ CT ]       │
        │               │          │
        │───────────────┘          │
        │               │          │
        │          Monitored Load  │
        │                          │
        └──────────────────────────┘
                         │
                         │
                    CT SECONDARY
                         │
                 ┌───────┴────────┐
                 │                │
              [18 Ω]             GND
             Burden
                 │
                 └───────┬────────
                         │
                       1 µF
                    Coupling Cap
                         │
                         ├────── GPIO34
                         │       ESP32 ADC
                         │
                    10 kΩ │
                         │
                    1.65 V Bias
                    ┌────┴────┐
                   10 kΩ    10 µF
                    │         │
                   GND       GND

The CT is installed around one current-carrying conductor, not around both live and neutral conductors together. If both conductors are passed through the same CT, their magnetic effects can largely cancel and the measurement may approach zero.

ESP32 Connections

GPIO34 is used in this example because it is an ADC-capable input on the original ESP32. Pin availability varies between ESP32 variants, so the board’s documentation should be checked before changing the wiring. Espressif documents the ADC interfaces and notes that ADC channels and characteristics differ between ESP32-family devices.

Creating the ADC Bias

The CT produces an AC waveform that swings both positive and negative.

An ESP32 ADC cannot directly accept a negative voltage, so the AC signal is shifted to approximately the middle of the ADC input range.

A pair of 10 kΩ resistors can create approximately:  3.3 V ÷ 2 = 1.65 V

The AC measurement signal is then coupled to this bias voltage through a capacitor.

This produces a waveform approximately centered around 1.65 V:

ADC Voltage

3.3 V       / \        / \
           /   \      /   \
1.65 V ---/-----\----/-----\----  DC bias
         /       \  /
0 V  ___/_________\/___________

This type of biased AC interface is a common approach for connecting CT signals to microcontroller ADC inputs. OpenEnergyMonitor describes the same general principle of converting the CT current to a voltage and positioning the resulting AC signal within the ADC input range.

Important CT Safety Connection

If the selected CT is a current-output CT, its secondary must have an appropriate burden connected. A current-output CT should not be left open-circuit while it is installed around a conductor carrying current because the secondary can develop a potentially dangerous voltage.

Voltage-output CTs with an integrated burden are different and should be connected according to their manufacturer’s specifications.

#include <Arduino.h>
#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>

// -----------------------------
// OLED configuration
// -----------------------------
#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 64

Adafruit_SSD1306 display(
  SCREEN_WIDTH,
  SCREEN_HEIGHT,
  &Wire,
  -1
);

// -----------------------------
// ESP32 ADC configuration
// -----------------------------
const int CT_PIN = 34;

// -----------------------------
// Electrical parameters
// -----------------------------

// Nominal AC supply voltage.
// Change this to match your installation.
const float AC_VOLTAGE = 230.0;

// Assumed power factor.
// For a simple current-only monitor,
// this is an approximation.
const float POWER_FACTOR = 1.0;

// CT example:
// 100 A primary / 0.050 A secondary
const float CT_PRIMARY_CURRENT = 100.0;
const float CT_SECONDARY_CURRENT = 0.050;

// Burden resistor used with the CT
const float BURDEN_RESISTOR = 18.0;

// -----------------------------
// Measurement parameters
// -----------------------------
const unsigned long SAMPLE_WINDOW_MS = 1000;

// Daily warning threshold
const float DAILY_LIMIT_KWH = 10.0;

// Accumulated energy
double dailyEnergyKWh = 0.0;

// Last measurement time
unsigned long lastEnergyUpdate = 0;

// -----------------------------
// Calculate RMS current
// -----------------------------
float readRMSCurrent()
{
  unsigned long startTime = millis();

  double sum = 0.0;
  double sumSquared = 0.0;

  unsigned long samples = 0;

  while (millis() - startTime < SAMPLE_WINDOW_MS)
  {
    float voltage = analogReadMilliVolts(CT_PIN) / 1000.0;

    sum += voltage;
    sumSquared += voltage * voltage;

    samples++;

    delayMicroseconds(200);
  }

  if (samples < 2)
  {
    return 0.0;
  }

  // Calculate average DC bias
  float averageVoltage = sum / samples;

  // Calculate AC RMS voltage
  double variance =
      (sumSquared / samples) -
      (averageVoltage * averageVoltage);

  if (variance < 0)
  {
    variance = 0;
  }

  float rmsVoltage = sqrt(variance);

  // CT secondary current
  float secondaryCurrent =
      rmsVoltage / BURDEN_RESISTOR;

  // Convert secondary current
  // to primary current
  float primaryCurrent =
      secondaryCurrent *
      (CT_PRIMARY_CURRENT / CT_SECONDARY_CURRENT);

  return primaryCurrent;
}

// -----------------------------
// Update energy calculation
// -----------------------------
void updateEnergy(float powerWatts)
{
  unsigned long now = millis();

  if (lastEnergyUpdate == 0)
  {
    lastEnergyUpdate = now;
    return;
  }

  unsigned long elapsedMs = now - lastEnergyUpdate;

  // Convert milliseconds to hours
  double elapsedHours =
      elapsedMs / 3600000.0;

  // Wh = W × hours
  double energyWh =
      powerWatts * elapsedHours;

  // Convert Wh to kWh
  dailyEnergyKWh += energyWh / 1000.0;

  lastEnergyUpdate = now;
}

// -----------------------------
// Display information
// -----------------------------
void updateDisplay(float currentA, float powerW)
{
  display.clearDisplay();

  display.setTextColor(SSD1306_WHITE);

  display.setTextSize(1);
  display.setCursor(0, 0);
  display.println("Daily Energy Monitor");

  display.setTextSize(1);
  display.setCursor(0, 16);
  display.print("Current: ");
  display.print(currentA, 2);
  display.println(" A");

  display.setCursor(0, 28);
  display.print("Power:   ");
  display.print(powerW, 0);
  display.println(" W");

  display.setCursor(0, 40);
  display.print("Today:   ");
  display.print(dailyEnergyKWh, 3);
  display.println(" kWh");

  display.setCursor(0, 54);

  if (dailyEnergyKWh >= DAILY_LIMIT_KWH)
  {
    display.print("Status: HIGH");
  }
  else
  {
    display.print("Status: NORMAL");
  }

  display.display();
}

// -----------------------------
// Setup
// -----------------------------
void setup()
{
  Serial.begin(115200);

  // ESP32 ADC
  analogReadResolution(12);

  // 11 dB attenuation allows a larger
  // input range on supported ESP32 devices.
  analogSetPinAttenuation(
    CT_PIN,
    ADC_11db
  );

  // OLED
  if (!display.begin(
        SSD1306_SWITCHCAPVCC,
        0x3C))
  {
    Serial.println("OLED initialization failed!");
    while (true)
    {
      delay(1000);
    }
  }

  display.clearDisplay();
  display.setTextColor(SSD1306_WHITE);
  display.setTextSize(1);

  display.setCursor(0, 0);
  display.println("Energy Monitor");

  display.setCursor(0, 15);
  display.println("Starting...");

  display.display();

  delay(2000);
}

// -----------------------------
// Main loop
// -----------------------------
void loop()
{
  // Measure RMS current
  float currentA = readRMSCurrent();

  // Estimate power
  float powerW =
      AC_VOLTAGE *
      currentA *
      POWER_FACTOR;

  // Accumulate energy
  updateEnergy(powerW);

  // Serial output
  Serial.println("-------------------------");

  Serial.print("Current: ");
  Serial.print(currentA, 2);
  Serial.println(" A");

  Serial.print("Power: ");
  Serial.print(powerW, 1);
  Serial.println(" W");

  Serial.print("Daily Energy: ");
  Serial.print(dailyEnergyKWh, 3);
  Serial.println(" kWh");

  if (dailyEnergyKWh >= DAILY_LIMIT_KWH)
  {
    Serial.println("WARNING: High daily consumption!");
  }
  else
  {
    Serial.println("Status: Normal");
  }

  // Update OLED
  updateDisplay(currentA, powerW);

  delay(100);
}

12. Displaying Daily Electricity Consumption

The display should focus on information that is useful to the user rather than presenting unnecessary technical data.

A practical main screen could show:

• Today’s Energy: 8.42 kWh
• Current Power: 620 W
• Current: 2.7 A
• Status: Normal

The display can also provide additional screens for:

• Today’s consumption
• Yesterday’s consumption
• Current power
• Maximum power
• Daily average
• Consumption history

Graphical Display

A TFT display can provide a simple graph showing how consumption changed during the day.

For example:

• 00:00 → Low consumption
• 08:00 → Increased activity
• 13:00 → Moderate consumption
• 18:00 → High consumption
• 23:00 → Low consumption

This is particularly useful because the project is not simply intended to produce a final kWh number. The historical pattern can help the user understand when the consumption increased.

13. Daily Energy Calculation and Data Storage

The monitor should have a clear definition of when a “day” begins and ends.

For example:

• 00:00 → Start new daily record
• 23:59 → Complete daily record

At midnight, the previous day’s accumulated energy can be stored and the daily counter can be reset.

A historical record could contain:

• This makes it easy to identify unusual days.
• The ESP32’s built-in memory can be used for small amounts of historical data, while an SD card or network-based storage is more appropriate if many months of records are required.
• A Wi-Fi-enabled version can also transmit daily readings to a computer, smartphone interface, or online dashboard.

14. Detecting Abnormal Electricity Consumption

One of the most useful features of this project is the ability to identify unusually high daily consumption.

The simplest approach is to establish a normal baseline.

For example:

Suppose the system records the following typical values:  Normal daily range: 7–9 kWh

If the monitor records:  12.5 kWh

The system can display: High Daily Consumption

• The monitor does not need to determine the exact appliance responsible.
• Instead, it tells the user that the total consumption was significantly different from the established pattern.

Possible Detection Methods

• A basic system can use a fixed threshold:  If Daily Energy > Threshold → Warning
• A more advanced system can calculate an average from previous days:   Average Daily Energy = Sum of Previous Days ÷ Number of Days
• The system can then compare today’s value with that historical baseline.

For example:

• if the typical consumption is around 8 kWh and today’s value is significantly higher, the display can flag the day for investigation.
• The threshold should be chosen carefully because electricity usage naturally changes from day to day. A higher value does not automatically mean there is a fault.

15. Calibration and Measurement Accuracy

• Calibration is essential if the monitor is expected to provide useful numerical measurements.
• The ESP32 ADC converts an analog voltage into a digital value, but the ADC reading alone does not tell the system how much electrical current is flowing.
• The software therefore needs a relationship between:  ADC Reading → Sensor Signal → Current → Power → Energy
• Calibration can be performed by comparing the monitor’s measurement against a trusted reference measurement.

For example:

1. Connect a known load.
2. Measure the load using a trusted meter.
3. Record the ESP32 measurement.
4. Calculate the correction factor.
5. Apply the calibration factor in software.
6. Repeat the test with different loads.

Calibration should ideally be performed under several operating conditions rather than only one load.

Sources of Error

Measurement errors can come from several sources:

• CT accuracy
• CT saturation
• Burden resistor tolerance
• ADC limitations
• Electrical noise
• Incorrect signal scaling
• Voltage variation
• Power-factor assumptions
• Phase errors
• Temperature
• Calibration errors

Analog Devices discusses CT-based energy measurement in terms of burden-resistor selection, phase error, sensor selection, and calibration, illustrating why accurate energy measurement involves more than simply reading a current sensor.

For a hobby project, the system can be sufficiently useful without laboratory-grade accuracy, but its limitations should be clearly understood.

16. Electrical Safety and Installation Considerations

This section is extremely important because the project involves electrical mains.

A CT sensor can provide a non-invasive measurement method, but installing it around a mains conductor still involves working near potentially lethal voltages.

A CT should be installed only according to the sensor manufacturer’s instructions.

A current-output CT also presents an important safety consideration: it should not be left open-circuited while installed around a conductor carrying current, unless the particular CT is specifically designed and protected against this condition.

Open Energy Monitor warns that an unburdened current-output CT can generate a potentially dangerous voltage at its secondary terminals.

The measurement circuit connected to the ESP32 must also be designed so that the voltage presented to the ADC remains within the appropriate input limits.

For a hobbyist project, the safest approach is generally to use:

• A properly rated CT sensor
• A purpose-designed isolated measurement module where appropriate
• Proper enclosure and insulation
• Correctly rated components
• A low-voltage isolated power supply for the electronics

Any installation involving mains wiring should be performed or checked by a suitably qualified person. The ESP32 and its low-voltage electronics should never be treated as a substitute for proper mains protection and installation practices.

17. Possible Improvements and Future Expansion

Once the basic daily monitor is working, the project can be expanded considerably.

Wi-Fi Monitoring

• Because ESP32 provides Wi-Fi connectivity, measurements can be transmitted to a local network or online dashboard.
• This allows the user to view consumption without being physically next to the display.

Historical Graphs

The system can store several days or months of data and generate graphs showing:

• Daily energy
• Weekly energy
• Monthly energy
• Peak power
• Average power

Automatic Alerts

The ESP32 can generate an alert when consumption exceeds a predefined threshold.

For example:  Today’s consumption has exceeded the expected daily limit.

Multiple Monitoring Channels

Several CT sensors can be used to monitor different circuits separately.

For example:

• Lighting circuit
• Office circuit
• Workshop circuit
• Air-conditioning circuit

This moves the project closer to circuit-level energy monitoring while still being different from true appliance-level identification.

More Accurate Energy Measurement

• A more advanced design can use dedicated energy-metering hardware instead of relying entirely on the ESP32 ADC.
• This can improve measurement accuracy and simplify some of the electrical measurement calculations.

Data Logging

Long-term data logging allows the user to identify patterns such as:

• Increasing monthly consumption
• Weekend versus weekday differences
• Seasonal changes
• Unusually high days
• Changes after replacing an appliance

This transforms the project from a simple display into a useful energy-monitoring and analysis system.

18. Frequently Asked Questions

Can this project measure the electricity used by each appliance?

• No. In its basic configuration, the system measures the combined consumption of all appliances connected to the monitored circuit.
• It can show that total consumption increased, but it cannot automatically determine that a particular refrigerator, television, or computer was responsible for the increase.

What is the main purpose of this project?

The primary purpose is to monitor total daily electricity consumption and determine whether the amount of energy used during the day is within the expected range.

Can I use a CT sensor with an ESP32?

Yes. A CT can provide an analog measurement signal that can be conditioned and read by the ESP32 ADC. The exact interface depends on the CT type and its output configuration.

Is measuring current enough to calculate electricity consumption?

• It can provide an estimate when a nominal voltage and appropriate assumptions are used, but it is less accurate than measuring voltage and current together.
• For accurate real-power measurement, voltage, current, and their phase relationship should be considered.

What does kWh mean?

A kilowatt-hour is a unit of energy. It represents the amount of energy consumed when a load with a power of 1 kilowatt operates for one hour.

Why should the sensor be installed around only one conductor?

• For a single-phase circuit, the current in the live and neutral conductors flows in opposite directions.
• If both conductors pass through the same CT, their magnetic effects can cancel, resulting in little or no useful measurement signal.

Can the ESP32 detect unusually high consumption?

Yes. The software can compare the accumulated daily energy with a predefined threshold or with historical daily averages and display a warning when consumption is unusually high.

Does a high daily consumption value prove that an appliance is faulty?

No. It only indicates that the total measured consumption was higher than expected. The user still needs to investigate which appliances were operating and determine the reason.

Can the project store previous days’ consumption?

Yes. Daily values can be stored in local memory, an SD card, or an external database, depending on how much historical data is required.

Can the system work without Wi-Fi?

Yes. Wi-Fi is not required for the basic measurement function. The ESP32 can measure, calculate, store, and display data locally.

Is this project suitable for beginners?

• Yes, if the project is divided into stages.
• Beginners can start with sensor reading and display functions before adding energy calculations, data logging, calibration, and abnormal-consumption detection.

19. Conclusion

The Smart Daily Electricity Consumption Monitor with ESP32 is a practical embedded-system project for monitoring the total electricity consumption of a selected group of appliances.

Its main objective is not to identify the energy consumption of every individual appliance. Instead, it continuously monitors the aggregate electrical consumption, calculates the accumulated energy used during the day, and presents the information in an understandable form.

This approach provides a simple way to establish a normal daily consumption pattern. If the measured energy is significantly higher than expected, the user can investigate which appliances were operating during that period and determine what caused the increase.

A basic implementation can use an ESP32, a suitable AC current sensor such as a CT, signal-conditioning circuitry, and a display. A more advanced implementation can add voltage measurement, real-power calculation, calibration, data logging, Wi-Fi connectivity, historical graphs, and automatic alerts.

For beginners, the project provides an accessible introduction to sensors, ADCs, embedded programming, electrical measurements, and data processing. For engineers and advanced hobbyists, it provides a foundation that can be extended into a more sophisticated energy-monitoring platform.

The most important design principle is to match the measurement method to the project’s objective: if the goal is to understand total daily electricity usage and identify unusual consumption, aggregate monitoring is sufficient; individual appliance measurement is not required.

                 AC MAINS
        ┌──────────────────────────┐
        │                          │
        │      LIVE CONDUCTOR      │
        │───────────────┐          │
        │               │          │
        │             [ CT ]       │
        │               │          │
        │───────────────┘          │
        │               │          │
        │          Monitored Load  │
        │                          │
        └──────────────────────────┘
                         │
                         │
                    CT SECONDARY
                         │
                 ┌───────┴────────┐
                 │                │
              [18 Ω]             GND
             Burden
                 │
                 └───────┬────────
                         │
                       1 µF
                    Coupling Cap
                         │
                         ├────── GPIO34
                         │       ESP32 ADC
                         │
                    10 kΩ │
                         │
                    1.65 V Bias
                    ┌────┴────┐
                   10 kΩ    10 µF
                    │         │
                   GND       GND

ADC Voltage

3.3 V       / \        / \
           /   \      /   \
1.65 V ---/-----\----/-----\----  DC bias
         /       \  /
0 V  ___/_________\/___________

#include <Arduino.h>
#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>

// -----------------------------
// OLED configuration
// -----------------------------
#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 64

Adafruit_SSD1306 display(
  SCREEN_WIDTH,
  SCREEN_HEIGHT,
  &Wire,
  -1
);

// -----------------------------
// ESP32 ADC configuration
// -----------------------------
const int CT_PIN = 34;

// -----------------------------
// Electrical parameters
// -----------------------------

// Nominal AC supply voltage.
// Change this to match your installation.
const float AC_VOLTAGE = 230.0;

// Assumed power factor.
// For a simple current-only monitor,
// this is an approximation.
const float POWER_FACTOR = 1.0;

// CT example:
// 100 A primary / 0.050 A secondary
const float CT_PRIMARY_CURRENT = 100.0;
const float CT_SECONDARY_CURRENT = 0.050;

// Burden resistor used with the CT
const float BURDEN_RESISTOR = 18.0;

// -----------------------------
// Measurement parameters
// -----------------------------
const unsigned long SAMPLE_WINDOW_MS = 1000;

// Daily warning threshold
const float DAILY_LIMIT_KWH = 10.0;

// Accumulated energy
double dailyEnergyKWh = 0.0;

// Last measurement time
unsigned long lastEnergyUpdate = 0;

// -----------------------------
// Calculate RMS current
// -----------------------------
float readRMSCurrent()
{
  unsigned long startTime = millis();

  double sum = 0.0;
  double sumSquared = 0.0;

  unsigned long samples = 0;

  while (millis() - startTime < SAMPLE_WINDOW_MS)
  {
    float voltage = analogReadMilliVolts(CT_PIN) / 1000.0;

    sum += voltage;
    sumSquared += voltage * voltage;

    samples++;

    delayMicroseconds(200);
  }

  if (samples < 2)
  {
    return 0.0;
  }

  // Calculate average DC bias
  float averageVoltage = sum / samples;

  // Calculate AC RMS voltage
  double variance =
      (sumSquared / samples) -
      (averageVoltage * averageVoltage);

  if (variance < 0)
  {
    variance = 0;
  }

  float rmsVoltage = sqrt(variance);

  // CT secondary current
  float secondaryCurrent =
      rmsVoltage / BURDEN_RESISTOR;

  // Convert secondary current
  // to primary current
  float primaryCurrent =
      secondaryCurrent *
      (CT_PRIMARY_CURRENT / CT_SECONDARY_CURRENT);

  return primaryCurrent;
}

// -----------------------------
// Update energy calculation
// -----------------------------
void updateEnergy(float powerWatts)
{
  unsigned long now = millis();

  if (lastEnergyUpdate == 0)
  {
    lastEnergyUpdate = now;
    return;
  }

  unsigned long elapsedMs = now - lastEnergyUpdate;

  // Convert milliseconds to hours
  double elapsedHours =
      elapsedMs / 3600000.0;

  // Wh = W × hours
  double energyWh =
      powerWatts * elapsedHours;

  // Convert Wh to kWh
  dailyEnergyKWh += energyWh / 1000.0;

  lastEnergyUpdate = now;
}

// -----------------------------
// Display information
// -----------------------------
void updateDisplay(float currentA, float powerW)
{
  display.clearDisplay();

  display.setTextColor(SSD1306_WHITE);

  display.setTextSize(1);
  display.setCursor(0, 0);
  display.println("Daily Energy Monitor");

  display.setTextSize(1);
  display.setCursor(0, 16);
  display.print("Current: ");
  display.print(currentA, 2);
  display.println(" A");

  display.setCursor(0, 28);
  display.print("Power:   ");
  display.print(powerW, 0);
  display.println(" W");

  display.setCursor(0, 40);
  display.print("Today:   ");
  display.print(dailyEnergyKWh, 3);
  display.println(" kWh");

  display.setCursor(0, 54);

  if (dailyEnergyKWh >= DAILY_LIMIT_KWH)
  {
    display.print("Status: HIGH");
  }
  else
  {
    display.print("Status: NORMAL");
  }

  display.display();
}

// -----------------------------
// Setup
// -----------------------------
void setup()
{
  Serial.begin(115200);

  // ESP32 ADC
  analogReadResolution(12);

  // 11 dB attenuation allows a larger
  // input range on supported ESP32 devices.
  analogSetPinAttenuation(
    CT_PIN,
    ADC_11db
  );

  // OLED
  if (!display.begin(
        SSD1306_SWITCHCAPVCC,
        0x3C))
  {
    Serial.println("OLED initialization failed!");
    while (true)
    {
      delay(1000);
    }
  }

  display.clearDisplay();
  display.setTextColor(SSD1306_WHITE);
  display.setTextSize(1);

  display.setCursor(0, 0);
  display.println("Energy Monitor");

  display.setCursor(0, 15);
  display.println("Starting...");

  display.display();

  delay(2000);
}

// -----------------------------
// Main loop
// -----------------------------
void loop()
{
  // Measure RMS current
  float currentA = readRMSCurrent();

  // Estimate power
  float powerW =
      AC_VOLTAGE *
      currentA *
      POWER_FACTOR;

  // Accumulate energy
  updateEnergy(powerW);

  // Serial output
  Serial.println("-------------------------");

  Serial.print("Current: ");
  Serial.print(currentA, 2);
  Serial.println(" A");

  Serial.print("Power: ");
  Serial.print(powerW, 1);
  Serial.println(" W");

  Serial.print("Daily Energy: ");
  Serial.print(dailyEnergyKWh, 3);
  Serial.println(" kWh");

  if (dailyEnergyKWh >= DAILY_LIMIT_KWH)
  {
    Serial.println("WARNING: High daily consumption!");
  }
  else
  {
    Serial.println("Status: Normal");
  }

  // Update OLED
  updateDisplay(currentA, powerW);

  delay(100);
}