Water Heater Fuel Type Cost Comparison Calculator
ANA›Life Services Authority›National Calculator Authority›Water Heater Fuel Type Cost Comparison Calculator
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Water Heater Fuel Type Cost Comparison Calculator
Compare the estimated annual operating costs of different water heater fuel types based on your household usage and local energy rates.
Number of People in Household
Cold Water Inlet Temperature (°F)
Hot Water Delivery Temperature (°F)
Electricity Rate ($/kWh)
Natural Gas Rate ($/therm)
Propane Rate ($/gallon)
Fuel Oil Rate ($/gallon)
Calculate Annual Costs
function watCalc() { var people = parseFloat(document.getElementById('wat-people').value); var tIn = parseFloat(document.getElementById('wat-inlet-temp').value); var tOut = parseFloat(document.getElementById('wat-outlet-temp').value); var elecRate = parseFloat(document.getElementById('wat-elec-rate').value); var gasRate = parseFloat(document.getElementById('wat-gas-rate').value); var propaneRate = parseFloat(document.getElementById('wat-propane-rate').value); var oilRate = parseFloat(document.getElementById('wat-oil-rate').value); var res = document.getElementById('wat-result');
// --- Validation --- if (isNaN(people) || people 20) { res.innerHTML = 'Please enter a valid number of people (1–20).'; return; } if (isNaN(tIn) || tIn 80) { res.innerHTML = 'Inlet temperature must be between 35°F and 80°F.'; return; } if (isNaN(tOut) || tOut 160) { res.innerHTML = 'Outlet temperature must be between 100°F and 160°F.'; return; } if (tOut Outlet temperature must be greater than inlet temperature.'; return; } if (isNaN(elecRate) || elecRate Please enter a valid electricity rate.'; return; } if (isNaN(gasRate) || gasRate Please enter a valid natural gas rate.'; return; } if (isNaN(propaneRate) || propaneRate Please enter a valid propane rate.'; return; } if (isNaN(oilRate) || oilRate Please enter a valid fuel oil rate.'; return; }
// --- Core Physics --- // Daily hot water usage: 18 gallons/person/day (DOE baseline) var dailyGal = 18 * people; var annualGal = dailyGal * 365;
// BTU needed per year: Q = m * Cp * ΔT // 1 gallon water = 8.33 lb; Cp water = 1 BTU/(lb·°F) var deltaT = tOut - tIn; var annualBTU = annualGal * 8.33 * 1.0 * deltaT; // BTU/year
// --- EF / UEF values (DOE/ENERGY STAR typical) --- // Electric Resistance: UEF ~0.92 // Natural Gas Storage: UEF ~0.64 // Propane Storage: UEF ~0.62 // Fuel Oil Storage: UEF ~0.62 // Heat Pump (HPWH): UEF ~3.50 // Tankless Gas: UEF ~0.82 // Tankless Electric: UEF ~0.99
var types = [ { name: 'Electric Resistance Storage', uef: 0.92, fuelType: 'electric', icon: '⚡' }, { name: 'Natural Gas Storage', uef: 0.64, fuelType: 'gas', icon: '🔥' }, { name: 'Propane Storage', uef: 0.62, fuelType: 'propane', icon: '🛢️' }, { name: 'Fuel Oil Storage', uef: 0.62, fuelType: 'oil', icon: '🛢️' }, { name: 'Heat Pump Water Heater', uef: 3.50, fuelType: 'electric', icon: '♻️' }, { name: 'Tankless Natural Gas', uef: 0.82, fuelType: 'gas', icon: '🔥' }, { name: 'Tankless Electric', uef: 0.99, fuelType: 'electric', icon: '⚡' } ];
// Energy content & cost per BTU for each fuel // Electric: 1 kWh = 3412 BTU // Natural Gas: 1 therm = 100,000 BTU // Propane: 1 gallon = 91,452 BTU // Fuel Oil: 1 gallon = 138,500 BTU
function annualCost(uef, fuelType) { var inputBTU = annualBTU / uef; // BTU of fuel consumed if (fuelType === 'electric') { var kWh = inputBTU / 3412; return kWh * elecRate; } else if (fuelType === 'gas') { var therms = inputBTU / 100000; return therms * gasRate; } else if (fuelType === 'propane') { var gallons = inputBTU / 91452; return gallons * propaneRate; } else if (fuelType === 'oil') { var gallons = inputBTU / 138500; return gallons * oilRate; } return 0; }
var results = types.map(function(t) { return { name: t.name, uef: t.uef, fuelType: t.fuelType, icon: t.icon, cost: annualCost(t.uef, t.fuelType) }; });
results.sort(function(a, b) { return a.cost - b.cost; });
var cheapest = results[0].cost; var mostExpensive = results[results.length - 1].cost;
// Build table var rows = ''; results.forEach(function(r, i) { var savings = r.cost - cheapest; var barPct = ((r.cost - cheapest) / (mostExpensive - cheapest + 0.01) * 100).toFixed(1); var badge = i === 0 ? ' Lowest Cost' : ''; rows += '' + '' + r.icon + ' ' + r.name + badge + '' + '' + r.uef.toFixed(2) + '' + '$' + r.cost.toFixed(2) + '' + '' + (savings > 0 ? '+$' + savings.toFixed(2) : '—') + '' + '' + ''; });
var annualGalFmt = annualGal.toLocaleString(); var annualBTUFmt = Math.round(annualBTU).toLocaleString();
res.innerHTML = '### Annual Operating Cost Comparison ' + 'Household: ' + people + ' people | ' + 'Daily Usage: ' + dailyGal.toFixed(0) + ' gal/day (' + annualGalFmt + ' gal/yr) | ' + 'ΔT: ' + deltaT + '°F | ' + 'Annual Heat Load: ' + annualBTUFmt + ' BTU
' + '' + '' + 'Water Heater Type' + 'UEF' + 'Annual Cost' + 'vs. Cheapest' + 'Relative Cost' + '' + rows + '' + '* Costs are estimates based on typical UEF values and your entered energy rates. Actual costs vary by unit, installation, and usage patterns.
'; }
#### Formula
Annual Heat Load (BTU): Q = Gallons/year × 8.33 lb/gal × 1 BTU/(lb·°F) × (Tout − Tin)
Annual Fuel Consumption: Fuel Input (BTU) = Q ÷ UEF
Annual Cost: Cost = Fuel Input (BTU) ÷ Energy Content per Unit × Rate per Unit
Energy Content: Electricity = 3,412 BTU/kWh | Natural Gas = 100,000 BTU/therm | Propane = 91,452 BTU/gal | Fuel Oil = 138,500 BTU/gal
#### Assumptions & References
- Hot water usage: 18 gallons per person per day (U.S. DOE baseline for storage water heaters).
- Water density: 8.33 lb/gallon; specific heat of water: 1 BTU/(lb·°F).
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