Poor (Older home, drafty)
Average (Standard insulation)
Excellent (New construction, energy star)
Est. Gallons Per Day
–
Est. Gallons Per Month
–
Daily Cost
–
Monthly Cost
–
*Calculations based on continuous heating at specified temperatures. Actual usage depends on wind, sun exposure, and water heating usage.
function calculateOilUsage() {
// Get Inputs
var homeSize = parseFloat(document.getElementById('homeSize').value);
var insulationFactor = parseFloat(document.getElementById('insulationRating').value);
var indoorTemp = parseFloat(document.getElementById('indoorTemp').value);
var outdoorTemp = parseFloat(document.getElementById('outdoorTemp').value);
var efficiency = parseFloat(document.getElementById('furnaceEfficiency').value);
var price = parseFloat(document.getElementById('oilPrice').value);
// Validation
if (isNaN(homeSize) || isNaN(indoorTemp) || isNaN(outdoorTemp) || isNaN(efficiency) || isNaN(price)) {
alert("Please enter valid numbers for all fields.");
return;
}
if (homeSize <= 0 || efficiency <= 0) {
alert("Size and Efficiency must be greater than zero.");
return;
}
// Logic
// 1 Gallon of heating oil ≈ 138,500 BTUs
var btuPerGallon = 138500;
// Temperature difference (Delta T)
var deltaT = indoorTemp – outdoorTemp;
// If it's warmer outside than inside, usage is zero (for heating)
if (deltaT <= 0) {
deltaT = 0;
}
// Heat Load Formula Estimation:
// BTU/hr Loss ≈ SqFt * InsulationFactor * DeltaT
// InsulationFactor is an approximation of U-Value * SurfaceAreaRatio
var btuLossPerHour = homeSize * insulationFactor * deltaT;
// Adjust for Furnace Efficiency
// Real BTUs needed = Loss / (Efficiency %)
var efficiencyDecimal = efficiency / 100;
var requiredBtuInput = btuLossPerHour / efficiencyDecimal;
// Convert BTUs to Gallons
var gallonsPerHour = requiredBtuInput / btuPerGallon;
// Time periods
var gallonsDay = gallonsPerHour * 24;
var gallonsMonth = gallonsDay * 30;
// Costs
var dailyCost = gallonsDay * price;
var monthlyCost = gallonsMonth * price;
// Display Results
document.getElementById('galPerDay').innerText = gallonsDay.toFixed(2) + " gal";
document.getElementById('galPerMonth').innerText = gallonsMonth.toFixed(1) + " gal";
document.getElementById('costPerDay').innerText = "$" + dailyCost.toFixed(2);
document.getElementById('costPerMonth').innerText = "$" + monthlyCost.toFixed(2);
// Show result section
document.getElementById('resultsSection').style.display = 'block';
}
Understanding Your Heating Oil Consumption
Managing heating costs is a priority for many homeowners in colder climates. Heating oil usage is not random; it follows the laws of thermodynamics based on your home's thermal retention properties, the efficiency of your burner, and the severity of the weather outside. This calculator estimates your burn rate by analyzing the heat loss of your property relative to the temperature differential.
Key Factors Affecting Oil Usage
Temperature Differential (Delta T): The greater the difference between your thermostat setting and the outdoor temperature, the faster heat escapes your home, requiring your furnace to run longer.
Home Size & Insulation: A larger surface area allows for more heat loss. However, "Insulation Quality" (often measured in R-values for walls/attics and U-values for windows) acts as a resistance barrier. A well-insulated home retains heat significantly longer than a drafty one.
Furnace Efficiency: Older oil boilers may operate at 70-75% efficiency, meaning 25-30% of the heat generated goes right up the chimney. Modern systems can reach efficiencies of 85-90% or higher.
K-Factor: Oil companies often use a "K-Factor" to predict your delivery. This is essentially "Degree Days per Gallon." If you have a high K-factor, your home is efficient; a low K-factor means you burn oil quickly.
Did you know? One gallon of heating oil contains approximately 138,500 BTUs of energy. If your furnace is 85% efficient, your home actually receives about 117,725 BTUs of heat per gallon burned.
How to Lower Your Oil Bill
Service Your System: Annual cleaning and tuning can improve efficiency by 5-10%. Soot buildup acts as an insulator inside the heat exchanger, preventing heat transfer to your home.
Install a Smart Thermostat: Lowering the temperature by just 5-10 degrees at night or when you are away can save 10% a year on heating bills.
Seal Drafts: Before upgrading expensive windows, look for air leaks around doors, windows, and basement rim joists. Caulk and weatherstripping are cheap and effective ways to reduce your "Heat Load."
Interpreting the Calculator Results
The "Gallons Per Day" figure provided above is an estimate based on the average outdoor temperature you entered. In reality, temperature fluctuates throughout the day. To get a seasonal estimate, you would typically look at the average temperature for a specific month in your region. For example, if the average January temperature in your area is 25°F, inputting that value will give you a projection for your peak winter spending.