AC & heating repair · San Marcos, Texas
AC repair and HVAC service in San Marcos, TX
AC quit, heat pump struggling, or a system near the end of its life? In San Marcos, 71% of homes heat with electricity[1] and half were built before 2001. Request service from HVAC contractors working here. San Marcos, in Hays County and Caldwell County and Guadalupe County — ZIP 78666, counts 77,830 residents (2025 estimate)[2].
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San Marcos HVAC snapshot: the key figures
- Population (2025 est.)
- 77,830[2]+14.9% since 2020
- County
- Hays / Caldwell / Guadalupe[2]city spans more than one county
- Land area
- 40.4 sq mi[3]
- Homes heated with electricity
- 71%[1]the 4th-highest share of the 15 Austin-area suburbs we cover
- Homes heated with utility gas
- 26%[1]plus 2% propane/LP
- Heat & excessive-heat days, hays zone
- 8[4]2016–2025
- Winter-storm & freeze days, hays zone
- 19[4]2016–2025; heating demand and freeze-related furnace failures
- Lightning-damage reports within 10 mi
- 0[4]2016–2025; power surges damage HVAC control boards
- Damaging-wind reports within 10 mi
- 35[4]2016–2025; wind-blown debris damages outdoor condenser units
- Homes built before 2000
- 48%[1]of 30,349 housing units
- Median year built
- 2001[1]the oldest of the 15 Austin-area suburbs we cover
What the local data means for HVAC in San Marcos
San Marcos counts 77,830 residents (2025 estimate), growing at a middle-of-the-pack 14.9% since 2020[2]. On the map that's 40.4 square miles holding 1,925 residents per square mile, the 9th densest of the suburbs here; it spans Hays County and Caldwell County and Guadalupe County, with ZIP code 78666[3].
With 33% of homes built in 2010 or later[1], a good share of San Marcos's equipment may still be under builder or manufacturer warranty; the 48% built before 2000 is where replacement jobs cluster.
The entire city sits in ZIP code 78666[5].
The tracked suburbs closest by are Kyle (8.9 mi N), Buda (14.8 mi N) and Dripping Springs (24.2 mi NW)[3].
71% of occupied San Marcos homes heat with electricity, 26% with utility gas and 2% with propane[1] — the 4th-highest electric share of the 15 Austin-area suburbs we cover; nearby, Kyle (51%), Buda (48%), and Dripping Springs (69%) heat electrically. Electric heat usually means one outdoor unit doing both jobs.
Hays County forecast zone, 2016–2025: 8 heat or excessive-heat days (latest Aug 20, 2024) and 19 winter-storm or hard-freeze days[4].
Storm exposure for HVAC hardware: 0 lightning-damage reports within 10 miles; 35 damaging-wind reports within 10 miles in 2016–2025[4]. Most recent: May 26, 2025, 0.5 miles from the city center.
48% of San Marcos's 30,349 housing units were built before 2000 and 33% since 2010[1] (pre-2000 share nearby: Kyle (13%), Buda (14%), and Dripping Springs (17%)). Check builder-installed equipment for a registered warranty.
Measured against the 15 suburbs on this site, San Marcos records the oldest housing (by median year built) (2001)[1] and the 3rd-lowest share of homes built since 2010 (33%)[1].
How air moves through a central system
How the loop runs: return duct to filter to air handler to supply ducts. A dirty filter slows everything downstream.
Get HVAC help in San Marcos
Requests go to AC & heating repair contractors serving the San Marcos area — ZIP code 78666.
Before reaching out: repair or replace? what a good hvac visit covers
The data underneath this San Marcos page
| Measure | San Marcos | Median of 15 | Difference |
|---|---|---|---|
| Built before 2000 | 48% | 17% | 32 pts higher |
| Damaging-wind reports (10 mi) | 35 | 24 | 11 more |
| Built 2010 or later | 33% | 50% | 17 pts lower |
| Utility-gas heat | 26% | 37% | 11 pts lower |
| Electric heat | 71% | 60% | 11 pts higher |
| Propane / LP heat | 2.5% | 2.2% | about the same |
| Median year built | 2001 | 2010 | 9 years older |
Sorted by largest difference. Each median is the middle value across the covered Austin-area suburbs, from the same sources.
| City | Freeze days | Lightning reports | Damaging-wind reports |
|---|---|---|---|
| San Marcos | 19 | 0 | 35 |
| Kyle 8.9 mi | 19 | 1 | 29 |
| Buda 14.8 mi | 19 | 3 | 19 |
| Dripping Springs 24.2 mi | 19 | 0 | 8 |
| Bee Cave 30.0 mi | 22 | 2 | 26 |
| Lakeway 33.4 mi | 22 | 1 | 20 |
| Date | Wind | Distance |
|---|---|---|
| May 26, 2025 | 64 mph (est.) | 0.5 mi |
| May 23, 2025 | 64 mph (est.) | 9.0 mi |
| May 22, 2025 | 61 mph | 4.2 mi |
| May 9, 2024 | 70 mph (est.) | 3.4 mi |
| May 9, 2024 | 60 mph (est.) | 1.8 mi |
| May 9, 2024 | 70 mph (est.) | 6.0 mi |
| Main heating fuel | Homes | Share | Margin of error |
|---|---|---|---|
| Electricity | 19,824 | 70.8% | ±1,136 |
| Utility gas | 7,340 | 26.2% | ±742 |
| Bottled or tank gas (propane, butane, etc.) | 687 | 2.5% | ±301 |
| No fuel used | 127 | 0.5% | ±80 |
| Coal or coke | 16 | 0.1% | ±25 |
| Solar energy | 10 | 0.0% | ±17 |
| Other fuel | 9 | 0.0% | ±15 |
| Built | Units | Share | Margin of error |
|---|---|---|---|
| 2020 or later | 2,153 | 7.1% | ±467 |
| 2010 to 2019 | 7,830 | 25.8% | ±774 |
| 2000 to 2009 | 5,734 | 18.9% | ±792 |
| 1990 to 1999 | 3,327 | 11.0% | ±623 |
| 1980 to 1989 | 4,319 | 14.2% | ±725 |
| 1970 to 1979 | 2,839 | 9.4% | ±548 |
| 1960 to 1969 | 1,341 | 4.4% | ±344 |
| 1950 to 1959 | 1,357 | 4.5% | ±308 |
| 1940 to 1949 | 742 | 2.4% | ±319 |
| 1939 or earlier | 707 | 2.3% | ±237 |
ACS 2020–2024 estimates; margins of error are the Census Bureau's 90% intervals.
| Measure | Value |
|---|---|
| Housing units | 30,349 |
| Detached single-family | 10,628 (35%) |
| Occupied homes | 28,013 |
| Owner-occupied | 8,630 (31%) |
| Renter-occupied | 19,383 (69%) |
| Median home value | $310,400 |
ACS 2020–2024 estimates.
| ZIP (ZCTA) | Share of San Marcos's land | Share of the ZIP inside the city |
|---|---|---|
| 78666 | 91% | 17% |
Dated heat and freeze records for the HAYS forecast zone: see the county list.
Common San Marcos HVAC questions
Are heat pumps common in San Marcos?
71% of San Marcos homes heat with electricity[1], which means a heat pump or electric resistance heat.
How old are San Marcos's homes — and their HVAC systems?
The median home dates to 2001, and 33% were built in 2010 or later[1]. Your own system may have been replaced since — the outdoor unit's data plate shows when it was made.
Which San Marcos ZIP codes are covered?
78666[5], Hays County. Nearby pages: Kyle (8.9 mi), Buda (14.8 mi), and Dripping Springs (24.2 mi)[3].
A lot of San Marcos homes predate 1980 — what does that mean for HVAC equipment work?
23% of San Marcos's housing units were built before 1980, 9.2% before 1960[1] — the highest share of the 15 Austin-area suburbs we cover. The ductwork in an older house is often original even when the equipment is not — ask for a duct leakage check with any replacement quote.
I rent in San Marcos. Who arranges the repair?
69% of occupied San Marcos homes are rented[1], the highest share of the 15 Austin-area suburbs we cover. Tell your landlord or property manager in writing first; your lease says who arranges repairs.
Sources
- Census ACS 2020–2024 5-year (keyless bulk)
- Census population estimates, Vintage 2025
- Census Gazetteer 2025
- NOAA Storm Events Database
- Census 2020 ZCTA–place file
Data pulled Sep 28, 2026. Full citations and method.