THTrue Home Cost
METHODOLOGY

Transparent math, clear limits, visible sources.

True Home Cost distinguishes what you entered, what we calculated, what is estimated, and what comes from a public source.

Core rule: We do not present a statewide benchmark as an exact parcel bill. If an exact local value is unavailable, the site keeps the limitation visible.

Mortgage principal and interest

For a standard fixed-rate mortgage, we use the conventional amortization formula. The loan principal equals purchase price minus down payment. The monthly interest rate is the annual percentage rate divided by 12, and the number of payments is the loan term in years multiplied by 12.

Recurring costs

Annual property tax and annual home insurance are divided by 12. HOA, utilities, and other recurring costs are monthly inputs. The maintenance reserve is a planning amount calculated as a percentage of the purchase price per year, divided by 12.

Property-tax benchmark

For ZIP codes that map to a county, the site calculates an effective property-tax benchmark directly from the U.S. Census Bureau's 2024 American Community Survey (ACS) 5-year detailed tables B25103 (median real-estate taxes paid) and B25077 (median owner-occupied home value). The benchmark is calculated as median real-estate taxes divided by median home value. ZIP-to-county mapping uses the Census Bureau's 2020 ZCTA-to-county relationship file; where a ZIP Code Tabulation Area intersects multiple counties, the county with the largest land-area intersection is selected as the primary county.

If a county benchmark is unavailable, the site falls back to the state-level effective-rate benchmark published by the Tax Foundation using Census ACS data. These are community-level benchmarks, not statutory tax rates or exact bills for an individual parcel.

The calculator can use a benchmark to suggest an annual property-tax amount from the purchase price. The visitor can accept that suggestion or replace it with a known tax amount. User-supplied values remain authoritative for the calculation.

What the current total does not automatically include

  • Closing costs or one-time purchase fees
  • Variable-rate mortgage changes
  • Mortgage insurance unless you enter it under other recurring costs
  • Special assessments unless you enter them
  • Future tax, insurance, utility, or HOA increases
  • Exact parcel-level property tax when only a broader benchmark is available

Electricity benchmark

The U.S. Energy Information Administration (EIA) publishes average retail electricity prices by state and sector. These are average revenues per kilowatt-hour, not individual utility tariff schedules. True Home Cost therefore labels the figure as an electricity benchmark and does not call it an exact utility rate or exact bill.

Data labels

  • Official: directly from a government or public authority source.
  • Benchmark: a source-backed community or statewide statistic used for planning, not an individual bill.
  • Derived: calculated from source/public inputs using a documented formula.
  • Estimated: a clearly labeled planning estimate.
  • User supplied: entered by the visitor.

Sources and freshness

Every published benchmark carries its source, period, and update date. We prefer authoritative public sources and do not fill missing coverage with invented numbers. County-level tax benchmarks and state-level electricity averages are available where coverage exists. Additional local utility tariffs and parcel-level records will be added only when authoritative, sufficiently complete sources are available.