Python Program to Calculate Electricity Bill

You can calculate the electricity bill in Python by taking the number of units consumed as input and applying a rate per unit, for example: bill = units * rate_per_unit.

Examples

Input50

OutputElectricity bill: 250.0

Input150

OutputElectricity bill: 750.0

Input0

OutputElectricity bill: 0.0

How to Think About It

To calculate the electricity bill, first get the number of units consumed from the user. Then multiply the units by a fixed rate per unit to find the total cost. This is like buying items where each item has a price, and you pay for how many you buy.

Algorithm

1

Get the number of units consumed as input

2

Set the rate per unit of electricity

3

Multiply units by rate to get the bill amount

4

Display the calculated bill

Code

python

units = float(input('Enter units consumed: '))
rate_per_unit = 5.0
bill = units * rate_per_unit
print('Electricity bill:', bill)

Output

Enter units consumed: 100
Electricity bill: 500.0

Dry Run

Let's trace the program with input 100 units.

1

Input units

User enters 100

2

Set rate

rate_per_unit = 5.0

3

Calculate bill

bill = 100 * 5.0 = 500.0

4

Print result

Print 'Electricity bill: 500.0'

units	rate_per_unit	bill
100	5.0	500.0

Why This Works

Step 1: Get input

We use input() to get the number of units consumed from the user as a string, then convert it to a float for calculation.

Step 2: Set rate

We define a fixed rate per unit, here 5.0, which means each unit costs 5 currency units.

Step 3: Calculate bill

We multiply the units by the rate using * operator to get the total bill.

Step 4: Display output

We print the result using print() so the user sees the total electricity bill.

Alternative Approaches

Using tiered rates

python

units = float(input('Enter units consumed: '))
if units <= 100:
    bill = units * 5
else:
    bill = 100 * 5 + (units - 100) * 7
print('Electricity bill:', bill)

This method uses different rates for first 100 units and remaining units, which is common in real bills.

Using function

python

def calculate_bill(units):
    rate = 5
    return units * rate
units = float(input('Enter units consumed: '))
bill = calculate_bill(units)
print('Electricity bill:', bill)

Encapsulates calculation in a function for reuse and clarity.

Complexity: O(1) time, O(1) space

Time Complexity

The program performs a fixed number of operations regardless of input size, so it runs in constant time O(1).

Space Complexity

It uses a few variables and no extra data structures, so space complexity is O(1).

Which Approach is Fastest?

All approaches run in constant time; using a function adds clarity but no significant speed difference.

Approach	Time	Space	Best For
Simple multiplication	O(1)	O(1)	Basic fixed rate calculation
Tiered rates	O(1)	O(1)	Realistic billing with slabs
Function encapsulation	O(1)	O(1)	Code reuse and clarity