A house can have reasonable utility bills and still be carrying an expensive heating and cooling problem. The seller may keep the thermostat at 78 degrees in summer, heat only occupied rooms, or rely on portable equipment. A mild billing period can also make tired equipment look economical.
Your job as a buyer is not to predict an exact monthly cost. It is to build a file that answers a more practical question: Will this home's heating and cooling costs strain my budget after I move in?
Paperwork matters. On October 17, 2026, ACHR News reported that some projects already underway may still qualify under the 179D deduction rules and that a mechanical-system designer for a public building may be owed a deduction. That 179D project-record story concerns commercial tax treatment, not residential home purchases. Its useful lesson for buyers is narrower: dates, scope, design responsibility, and supporting records can determine what a mechanical project is actually worth.
Start with 12 months of utility records
Ask for complete electric and fuel records, not a seller's estimate or one convenient bill. Record the billing dates, usage units, and cost separately. Price changes can move the total even when consumption stays similar.
Then ask how the house was operated during that period. How many people lived there? Were any rooms closed? Was the house vacant for part of the year? What thermostat settings were typical? Did fireplaces, space heaters, window air conditioners, or dehumidifiers carry part of the load? The answers do not invalidate the bills. They tell you how closely those bills resemble your expected use.
Identify every piece of comfort equipment
Make a list of the furnace, boiler, heat pump, air conditioner, mini-splits, thermostats, humidifier, dehumidifier, electronic air cleaner, condensate pumps, and powered ventilators. Photograph each nameplate. Record model and serial numbers, installation dates if documented, fuel type, and which rooms or zones each unit serves.
Do not treat age as a diagnosis. An older system may be operating correctly, while a newer installation may have drainage, airflow, control, or workmanship problems. Ask for invoices showing installation, maintenance, refrigerant work, motor replacement, leak repairs, and recurring fault codes. A verbal claim that the system was serviced is less useful than a dated work order describing what was tested and changed.
Give the inspector better questions
A general home inspection should identify visible conditions, but buyers should clarify what will actually be operated and measured. Ask whether the inspector will run each mode that outdoor conditions safely permit, check temperature change across the equipment, inspect accessible ductwork, test condensate disposal, note filter size and condition, and identify obvious combustion or venting concerns.
Ask what is excluded. If performance, combustion, refrigerant charge, boiler operation, or concealed ductwork falls outside the inspection, get an HVAC contractor's evaluation before the contingency deadline. Do not ask only whether the system works. Ask what is failing, what cannot be tested, and what deserves a repair estimate.
Look beyond the mechanical room. Attic duct damage, roof penetrations, blocked soffit ventilation, and water stains can cross trade boundaries. If moisture appears near a flue, rooftop unit, or attic air handler, coordinate the HVAC inspection with a roofing contractor such as Keys Roofing so each contractor can define the part of the assembly being evaluated.
Collect estimates that can be compared
For every flagged item, request a written estimate with the equipment or component identified, the proposed scope, permit responsibility, electrical or gas work, access work, disposal, warranty terms, and exclusions. Separate urgent repairs from optional upgrades. A replacement quote should also state whether duct changes, drain changes, controls, pads, line sets, or electrical work are included.
Do not reduce several different scopes to one bottom-line number. One contractor may be pricing a component repair, another a complete system, and a third a system plus duct correction. Put them on the worksheet before deciding what belongs in your offer, immediate move-in budget, or longer-term plan.
Printable home HVAC comparison worksheet
Property: __________ Visit date: __________ Inspector: __________
Utility record: Months supplied ____ Electric usage range ____ Gas or fuel usage range ____ Occupancy notes ____ Thermostat settings ____ Supplemental heating or cooling ____
Equipment: Type ____ Brand and model ____ Documented installation date ____ Area served ____ Service records available: Yes / No ____ Observed operating mode ____
Inspection questions: All zones tested: Yes / No ____ Accessible ducts checked: Yes / No ____ Condensate route checked: Yes / No ____ Combustion or venting review needed: Yes / No ____ Specialist follow-up required ____
Estimate comparison: Contractor ____ Repair scope ____ Replacement scope ____ Included electrical, duct, drain, permit, and access work ____ Exclusions ____ Warranty ____ Estimate total ____
Buyer budget: Work needed before occupancy ____ First-year work ____ Optional later work ____ Unresolved conditions ____ Documentation still requested ____
Print one sheet for each property. The goal is not to turn a home tour into a mechanical audit. It is to keep attractive finishes from burying the operating history, inspection gaps, and repair scopes that will shape your real comfort budget.