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The real number is $274/mo — 15.2% of rent — not the $0 the good months suggest. The roof does not care about your cash flow timing.
Every landlord learns the reserve lesson once, in July, when the HVAC dies. The rules of thumb (1% of value, $1/sqft, 10% of rent) average across every house; the itemized schedule prices yours: roof $12,000 with 25 years left, HVAC $7,000 with 15, water heater $1,400 with 12, appliances $2,500 with 10 — $184/month of CapEx, plus $90 of routine maintenance at 5% of rent, $274 total, 15.2% of the rent check. Funded monthly into a separate account, capital expenses stop being emergencies and start being scheduled events. This calculator builds your itemized schedule from your equipment's actual remaining life.
Landlords use it before trusting cash flow: itemized reserves price out at $274/mo (15.2% of rent) — the 1% rule averages across houses, but your HVAC dies on YOUR schedule, in July.
Because the 1% rule describes an average house and you own a specific one. A rental with a 3-year-old roof and a 14-year-old HVAC has a completely different reserve need than the reverse — the rule gives both the same number, and one of them gets surprised. Itemizing also exposes the near-term cliff: the roof with 25 years left reserves $40/month; the same roof with 5 years left reserves $200. The method: walk the property and list every capital item with a replacement cost and remaining life — roof, HVAC, water heater, appliances, flooring, exterior paint, water softener, garage door opener — then reserve cost ÷ years for each. The items that ambush landlords most: water heaters (8–12 years, they fail by leaking, and the leak is the expensive part), HVAC (12–18 years, always dies in peak season at emergency rates), and sewer lines on pre-1980 homes. Update the schedule annually — remaining life shrinks every year, which is exactly the point of the exercise.
Five to ten percent of rent, scaling with age and wear. The 5% end: newer construction, long-term careful tenants, and systems all mid-life. The 10% end: older homes (pre-1980), high tenant turnover (every make-ready is maintenance), and deferred maintenance you are catching up on. What routine covers: the $150–400 service calls — plumbing clogs, garbage disposals, outlet replacements, HVAC filters and tune-ups, pest control, gutter cleaning — plus the annual items like HVAC servicing ($150–250) that extend the life of the CapEx items and are cheaper than the replacements they delay. What it does not cover: anything with a serial number that gets replaced whole — that is CapEx. The behavioral trick that matters more than the percentage: separate account, automatic transfer, no exceptions in profitable months. Landlords who commingle reserves with operating cash discover, empirically, that reserves evaporate. At the defaults this is $274/month; the landlord who banks it for 5 years has $16,440 and capital expenses become scheduling decisions instead of financing emergencies.
They should — under-reserved cash flow is fake cash flow. A deal that cash-flows $300/month with a $274 reserve actually cash-flows $26, and one with $200 of apparent flow is losing money honestly accounted. Run every purchase proforma with the itemized reserve from this calculator, not the seller's maintenance number — sellers selling a rental have spent the last two years NOT maintaining it, which is frequently why it is for sale. The inspection-informed adjustment: whatever the inspection says about remaining life on roof and HVAC goes directly into this calculator before you close, and if the reserve eats the deal, the deal was never there. The flip side: a property with fresh roof, HVAC, and water heater has years of low reserve needs — part of why light-rehab deals beat heavy-rehab ones for buy-and-hold cash flow. Depreciation interacts here too: capital replacements depreciate over 5–27.5 years while repairs deduct now, so the tax profile of a heavy-CapEx property differs from a light one — worth a conversation with your CPA at purchase, not at the first replacement.