The true monthly cost of a Treasure Valley home.
Your lender quotes principal and interest. That's half the number. This tool shows the full stack — CID tax, irrigation, homeowner's exemption, maintenance reserve — and what happens when you shift the rate, raise the down payment, or take a seller buy-down. Before you write an offer, not after.
Line by line
Scenario A
Scenario B
Where your money goes over 30 years
Your equity over time
Year-by-year amortization
| Year | Balance | Interest paid | Principal paid | Equity (~) |
|---|
Three paths, one decision
Most calculators stop at principal and interest. In the Treasure Valley, that's half the number.
CID, irrigation, exemption status, septic reserves, HOA — these are the line items that separate a payment that fits your life from a payment that owns it. We built this because we were tired of watching buyers anchor on a sticker price and discover the stack at closing. If you want the real number on a specific target home, that's a phone call — but this gets you close enough to ask the right questions.
Ready for the real number on a real house?
We run these numbers on specific target homes every day. The math is the same — the difference is we know which taxing district the house sits in, which subdivision carries CID, and what irrigation actually costs. That's a 15-minute call.
Where these numbers come from
Every assumption this calculator makes, and the source behind it. Last verified September 9, 2026.
- Property tax rates
- Ada 0.642%, Canyon 0.612%, Gem 0.356%, Payette 0.559% of assessed value. Idaho State Tax Commission, 2025 Average Property Tax Rates (EPB00129), overall county average. Ada runs 0.652% inside city limits and 0.560% rural.
- Homeowner's exemption
- 50% of value up to $125,000, primary residence only. Idaho State Tax Commission. The exemption covers the home and up to one acre, so on larger parcels your real exemption is smaller than this tool assumes.
- Starting interest rate
- 6.71%, the 30 year fixed average for the week of September 3, 2026. Freddie Mac Primary Mortgage Market Survey. Your rate depends on credit, loan type, and lender pricing.
- Homeowner's insurance
- 0.35% of price per year. Published Idaho averages run $1,673 to $2,240 per year across Insure.com, MoneyGeek, and LendingTree (2026). Premiums track rebuild cost, not purchase price, so this is an estimate.
- Mortgage insurance
- 0.7% of the loan per year when you put less than 20% down. Industry range is 0.5% to 1.5%; the prime borrower average runs 0.6% to 0.9%. It ends automatically at 78% loan to value under the federal Homeowners Protection Act, and you can request removal at 80%.
- Maintenance reserve
- 1% of price per year. A long standing planning rule of thumb, not a measured figure. Older homes and larger lots run higher.
- Utilities
- $260 per month. Published Treasure Valley averages are about $235 in Boise and $198 in Meridian for electric, water, sewer and trash, plus roughly $64 for natural gas. Idaho Power raised residential rates 9.74% in 2026.
- Community Infrastructure Districts
- Harris Ranch and Avimor levy formulas from the districts' own published rates and Ada County levy filings. Harris Ranch assumes an 8,000 square foot lot for the per square foot special assessment.
- Submarket medians
- Median sold price, sourced per city and dated next to each figure. Boise, Meridian, Nampa and Caldwell are Redfin July 2026; Kuna is Redfin May 2026; Star, Emmett and Fruitland still carry their March 2026 Intermountain MLS values and are labelled as not re-verified. Eagle is shown as a range because sold medians there ran from $799K to $905K depending on the source. Asking-price figures are excluded throughout. These are context only and never feed the calculation, which always uses the price you enter.
Sources disagree on insurance and utilities, so those two are shown as ranges above and set to a mid range default in the tool. Both are editable. If a number matters to your decision, we pull the real one for the specific address before you write an offer.