Understanding your electricity bill starts with knowing two main components: your usage in kilowatt-hours (kWh) and the rate you are charged per kWh. Many utility bills are confusing, often separating "supply" charges from "delivery" charges. This calculator combines these factors to give you a clear estimate of your monthly costs.
The Basic Formula
The mathematical formula to calculate your electricity bill is relatively straightforward:
(Monthly Usage in kWh × Rate per kWh) + Fixed Monthly Fees = Total Bill
Key Terms Explained
Kilowatt-Hour (kWh): This is the unit of measurement for electricity usage. Running a 1,000-watt appliance (like a microwave) for one hour consumes 1 kWh.
Cents per kWh: The price you pay for every unit of energy. In the United States, this typically ranges from 10¢ to 30¢ depending on your state. Note that this often includes both generation (making the power) and transmission (bringing it to your home).
Fixed Base Charge: A flat monthly fee charged by your utility provider to maintain the grid connection and metering equipment, regardless of how much power you use.
Average Appliance Energy Consumption
To better estimate your Monthly Usage input, here is a reference table for common household appliances:
Appliance
Avg. Wattage
Est. Monthly Cost (at 14¢/kWh)
Refrigerator
150-400 Watts
$5 – $15
Central Air Conditioning
3,500 Watts
$80 – $200 (Summer)
Water Heater (Electric)
4,500 Watts
$40 – $60
LED Light Bulb (x10)
10 Watts each
$1 – $2
Desktop Computer
200 Watts
$3 – $8
How to Lower Your Rate
In deregulated energy markets, you have the option to switch your electricity supplier. While the utility company (the one that owns the wires) stays the same, you can often find a lower supply rate (cents per kWh) by shopping around. Use the calculator above to compare your current bill against a competitor's offer by changing the "Electricity Rate" field.
function calculateBill() {
// 1. Get input values using specific IDs
var usageInput = document.getElementById('monthlyUsage');
var rateInput = document.getElementById('costPerKwh');
var feeInput = document.getElementById('baseFee');
var taxInput = document.getElementById('taxRate');
// 2. Parse values, handling empty inputs as 0
var usage = parseFloat(usageInput.value) || 0;
var rateCents = parseFloat(rateInput.value) || 0;
var fixedFee = parseFloat(feeInput.value) || 0;
var taxPercent = parseFloat(taxInput.value) || 0;
// 3. Perform Calculations
// Convert rate from cents to dollars (e.g., 14 cents = $0.14)
var rateDollars = rateCents / 100;
// Calculate pure energy cost
var energyCost = usage * rateDollars;
// Calculate subtotal before tax
var subtotal = energyCost + fixedFee;
// Calculate tax amount
var taxAmount = subtotal * (taxPercent / 100);
// Calculate final total monthly bill
var totalMonthly = subtotal + taxAmount;
// Calculate annual estimate
var totalAnnual = totalMonthly * 12;
// 4. Update the UI results
document.getElementById('displayEnergyCost').innerHTML = '$' + energyCost.toFixed(2);
document.getElementById('displayFixedCost').innerHTML = '$' + fixedFee.toFixed(2);
document.getElementById('displayTax').innerHTML = '$' + taxAmount.toFixed(2);
document.getElementById('displayTotal').innerHTML = '$' + totalMonthly.toFixed(2);
document.getElementById('displayAnnual').innerHTML = '$' + totalAnnual.toFixed(2);
// 5. Show the results container
document.getElementById('results').style.display = 'block';
}