C Program to Calculate Electricity Bill

The electricity bill is calculated by multiplying the unit generated by the cost per unit. ie, if the unit generated is 190(say) and the cost per unit is 10Rs so the total electricity bill is 190×10 = 1900Rs.

Although the electric meters installed at our houses read the electricity consumed in kilowatt-hours(kwh) and 1 kwh is equal to 1 unit.

So during calculation 1kwh and 1unit means the same thing.

Write a C program to calculate electricity bill.

1. Take input from the user.
2. Calculate the electricity bill using if else ladder.
3. Print the result.

Example:
Suppose the rate of electricity bill is as followed:

• For 1 to 50 units – 30Rs/unit
• For 50 to 100 units – 35Rs/unit
• For 100 to 150 units – 40Rs/unit
• For 150 units and above – 50Rs/unit

So calculate the electricity bill for 300 units?

Solution:

So the total electricity bill be 1500 + 1750 + 2000 + 7500 = 12,750 Rs.

Here is source code of the C program to calculate electricity bill. The C program is successfully compiled and run on a Linux system. The program output is also shown below.

/*
 * C Program to Calculate Electricity Bill
 */
 
#include <stdio.h>
 
// 1 to 50 units  - 30Rs/unit
// 50 to 100 units - 35Rs/unit
// 100 to 150 units - 40Rs/unit
// 150 units and above - 50Rs/unit
 
int electricity_bill(int units)
{
    if (units <= 50)
    {
        return units * 30;
    }
    else if (units <= 100)
    {
        return (50 * 30) + (units - 50) * 35;
    }
    else if (units <= 150)
    {
        return (50 * 30) + (50 * 35) + (units - 100) * 40;
    }
    else
    {
        return (50 * 30) + (50 * 35) + (50 * 40) + (units - 150) * 50;
    }
}
int main()
{
    int units;
    printf("Enter the units: ");    
    scanf("%d", &units);
    printf("The electricity bill is: %d\n", electricity_bill(units));
    return 0;
}

1. Use the scanf() function to get user input for units and store it in units variable.
2. Create a function named electricity_bill and passed the parameter units entered by the user.
3. using if – else if and else ladder specify the condition that says if units is less than 50 then return product of units and 30, else if the units is less than 100 it means it has to return 1st 50 units at 30 Rs rate and remaining at 35 Rs rate. So return (50 × 30) + (units – 50) × 35 and so on for other ranges.
4. Print the result using printf() function.

Time Complexity: O(1)
The time Complexity to calculate electricity bill is O(1) as the program is taking constant time. ie, no any loop or recursive call is made.

Space Complexity: O(1)
The space Complexity to calculate electricity bill is O(1) as the program require no auxiliary space. ie, no any data structure is required to store the data.

Testcase 1: In this case, we input “300” as units to calculate the electricity bill. (1 to 50 units – 30Rs/unit, 50 to 100 units – 35Rs/unit, 100 to 150 units – 40Rs/unit and 150 units and above – 50Rs/unit)

Enter the units: 300
The electricity bill is: 12750

Testcase 2: In this case, we input “180” as units to calculate the electricity bill. (1 to 50 units – 30Rs/unit, 50 to 100 units – 35Rs/unit, 100 to 150 units – 40Rs/unit and 150 units and above – 50Rs/unit)

Enter the units: 180
The electricity bill is: 6750

To practice programs on every topic in C, please visit “Programming Examples in C”, “Data Structures in C” and “Algorithms in C”.