Home Energy Audit Calculator

Home Energy Audit is evaluated from Home Size, Annual Heating Degree Days and Annual Cooling Degree Days. The calculation reports Annual Heating Cost, Annual Cooling Cost and Annual Water Heating Cost.

Results

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About the Home Energy Audit Calculator

Home Energy Audit is treated here as a quantitative relation between Home Size, Annual Heating Degree Days, Annual Cooling Degree Days and Natural Gas Rate and Annual Heating Cost, Annual Cooling Cost, Annual Water Heating Cost and Total Estimated Annual Energy Cost.

The calculator uses a multi formula configuration. Each reported value is read as a direct evaluation of the stored rules with the declared field formats and units.

Formula basis:
Heating cost: UA load x HDD x 24 / furnace efficiency → therms x gas rate
Cooling cost: tons x BTU/hr / EER x CDD hours x electricity rate
Other (appliances + lighting): 3 kWh/sq ft x electricity rate

Interpret the outputs in the order shown by the result fields. Optional inputs affect only the outputs that depend on those variables.

Formula & How It Works

The calculation applies the following relations exactly as recorded in the metadata:

Heating cost: UA load x HDD x 24 / furnace efficiency → therms x gas rate
Cooling cost: tons x BTU/hr / EER x CDD hours x electricity rate
Other (appliances + lighting): 3 kWh/sq ft x electricity rate

Each output field is produced by substituting the supplied inputs into the relevant relation and then applying the declared rounding or text format.

Worked Examples

Example 1: 2,000 sq ft Chicago home, 1990s construction, gas $1.20/therm, electricity $0.16/kWh

Inputs

home_sqft: 2000 hdd: 5000 cdd: 1000 gas_rate: 1.2 elec_rate: 0.16 home_age: 1.00
Annual Heating Cost: $1,565/year. Annual Cooling Cost: $3,762/year. Annual Water Heating Cost: $60/year. Total Estimated Annual Energy Cost: $6,347/year

With Home Size = 2,000, Annual Heating Degree Days = 5,000, Annual Cooling Degree Days = 1,000 and Natural Gas Rate = 1.2 as the stated inputs, the result is Annual Heating Cost = $1,565/year, Annual Cooling Cost = $3,762/year and Annual Water Heating Cost = $60/year. Each value corresponds to the declared output fields.

Example 2: 1,500 sq ft Houston home, 1980s construction, gas $1.00/therm, electricity $0.13/kWh

Inputs

home_sqft: 1500 hdd: 1500 cdd: 3500 gas_rate: 1 elec_rate: 0.13 home_age: 0.70
Annual Heating Cost: $419/year. Annual Cooling Cost: $8,023/year. Annual Water Heating Cost: $38/year. Total Estimated Annual Energy Cost: $9,065/year

With Home Size = 1,500, Annual Heating Degree Days = 1,500, Annual Cooling Degree Days = 3,500 and Natural Gas Rate = 1 as the stated inputs, the result is Annual Heating Cost = $419/year, Annual Cooling Cost = $8,023/year and Annual Water Heating Cost = $38/year. Each value corresponds to the declared output fields.

Example 3: 3,500 sq ft Boston home, pre-1970 construction, oil heat ($3.80/gal), electricity $0.25/kWh

Inputs

home_sqft: 3500 hdd: 6500 cdd: 500 gas_rate: 1.6 elec_rate: 0.25 home_age: 0.40
Annual Heating Cost: $11,870/year. Annual Cooling Cost: $5,143/year. Annual Water Heating Cost: $140/year. Total Estimated Annual Energy Cost: $19,777/year

With Home Size = 3,500, Annual Heating Degree Days = 6,500, Annual Cooling Degree Days = 500 and Natural Gas Rate = 1.6 as the stated inputs, the result is Annual Heating Cost = $11,870/year, Annual Cooling Cost = $5,143/year and Annual Water Heating Cost = $140/year. Each value corresponds to the declared output fields.

Example 4: 2,500 sq ft Phoenix home, 2010s construction, electricity only, $0.13/kWh (APS)

Inputs

home_sqft: 2500 hdd: 500 cdd: 4500 gas_rate: 1.2 elec_rate: 0.13 home_age: 1.30
Annual Heating Cost: $151/year. Annual Cooling Cost: $17,192/year. Annual Water Heating Cost: $75/year. Total Estimated Annual Energy Cost: $18,392/year

With Home Size = 2,500, Annual Heating Degree Days = 500, Annual Cooling Degree Days = 4,500 and Natural Gas Rate = 1.2 as the stated inputs, the result is Annual Heating Cost = $151/year, Annual Cooling Cost = $17,192/year and Annual Water Heating Cost = $75/year. Each value corresponds to the declared output fields.

Common Use Cases

  • Estimate annual home energy costs across all end uses
  • Identify largest energy consumers in the home
  • Prioritize home energy efficiency upgrades