Energy Savings Calculator
ANA›Life Services Authority›National Calculator Authority›Energy Savings Calculator
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Energy Savings Calculator
Estimate annual energy consumption and cost savings when upgrading from an existing HVAC system to a higher-efficiency model.
Peak Cooling Load (tons)
Annual Operating Hours (hrs/yr)
Existing System Efficiency (SEER or EER)
New System Efficiency (SEER or EER)
Electricity Rate ($/kWh)
Calculate Savings
function eneCalc() { var resultDiv = document.getElementById("ene-result");
var coolingLoad = parseFloat(document.getElementById("ene-cooling-load").value); var hours = parseFloat(document.getElementById("ene-hours").value); var oldSeer = parseFloat(document.getElementById("ene-old-seer").value); var newSeer = parseFloat(document.getElementById("ene-new-seer").value); var rate = parseFloat(document.getElementById("ene-rate").value);
// --- Validation --- if (isNaN(coolingLoad) || coolingLoad 500) { resultDiv.innerHTML = "Please enter a valid peak cooling load between 0.5 and 500 tons.
"; return; } if (isNaN(hours) || hours 8760) { resultDiv.innerHTML = "Please enter valid annual operating hours between 100 and 8,760.
"; return; } if (isNaN(oldSeer) || oldSeer 30) { resultDiv.innerHTML = "Please enter a valid existing system efficiency (SEER/EER) between 6 and 30.
"; return; } if (isNaN(newSeer) || newSeer 40) { resultDiv.innerHTML = "Please enter a valid new system efficiency (SEER/EER) between 6 and 40.
"; return; } if (newSeer 1.00) { resultDiv.innerHTML = "Please enter a valid electricity rate between $0.01 and $1.00 per kWh.
"; return; }
// --- Core Formulas --- // 1 ton of cooling = 12,000 BTU/hr // EER (BTU/Wh) = SEER * 0.875 (industry approximation for mixed-load conversion) // Annual BTU load = coolingLoad (tons) * 12,000 (BTU/hr/ton) * hours (hr/yr) // kWh = Annual BTU load / (EER * 1000) [EER in BTU/Wh → divide by 1000 for kWh] // Savings kWh = kWh_old - kWh_new // Savings $ = Savings kWh * rate
var btuPerTon = 12000; // BTU/hr per ton var annualBtu = coolingLoad * btuPerTon * hours; // BTU/yr
// Convert SEER to EER for annual energy calculation var eerOld = oldSeer * 0.875; var eerNew = newSeer * 0.875;
var kwhOld = annualBtu / (eerOld * 1000); var kwhNew = annualBtu / (eerNew * 1000);
var kwhSavings = kwhOld - kwhNew; var costOld = kwhOld * rate; var costNew = kwhNew * rate; var costSavings = kwhSavings * rate; var pctSavings = (kwhSavings / kwhOld) * 100;
// Simple payback helper (rough installed cost estimate: $500–$800/ton for new unit) // We show savings only; payback requires install cost input (not in scope here)
resultDiv.innerHTML = "### Results " + "" + "MetricExisting SystemNew System" + "Efficiency (SEER)" + oldSeer.toFixed(1) + "" + newSeer.toFixed(1) + "" + "Equivalent EER" + eerOld.toFixed(2) + " BTU/Wh" + eerNew.toFixed(2) + " BTU/Wh" + "Annual Energy Use" + kwhOld.toLocaleString(undefined,{maximumFractionDigits:0}) + " kWh" + kwhNew.toLocaleString(undefined,{maximumFractionDigits:0}) + " kWh" + "Annual Energy Cost$" + costOld.toLocaleString(undefined,{minimumFractionDigits:2,maximumFractionDigits:2}) + "$" + costNew.toLocaleString(undefined,{minimumFractionDigits:2,maximumFractionDigits:2}) + "" + "" + "" + "Annual Energy Savings: " + kwhSavings.toLocaleString(undefined,{maximumFractionDigits:0}) + " kWh (" + pctSavings.toFixed(1) + "% reduction)" + "Annual Cost Savings: $" + costSavings.toLocaleString(undefined,{minimumFractionDigits:2,maximumFractionDigits:2}) + ""; }
#### Formulas Used
Annual BTU Load: Annual BTU = Cooling Load (tons) × 12,000 BTU/hr/ton × Operating Hours (hr/yr)
EER Conversion: EER (BTU/Wh) ≈ SEER × 0.875 (Accounts for mixed part-load vs. full-load operation per AHRI Standard 210/240)
Annual Energy Consumption: kWh = Annual BTU Load ÷ (EER × 1,000)
Annual Savings: ΔkWh = kWhold − kWhnew ΔCost ($) = ΔkWh × Electricity Rate ($/kWh)
#### Assumptions & References
- SEER-to-EER conversion factor of 0.875 is an industry-standard approximation per AHRI Standard 210/240 and widely used in DOE energy analyses.
- Minimum federal SEER standard for residential central AC (as of 2023): 14 SEER (North) / 15 SEER (South) per DOE 10 CFR Part 430.
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