Sizing first, then the system type, then efficiency, then features. Homeowners usually work that list backwards, and the two decisions that matter most get made last.

Sizing Is the Decision That Matters Most

The most consequential choice is capacity, and the most common error is matching the BTU rating of the furnace being removed.

That is fast, it feels safe, and it perpetuates whatever mistake was made originally. Oversizing is the usual error, and it produces short cycling, uneven temperatures, and accelerated wear on ignition components.

Correct sizing comes from a load calculation using your home’s square footage, insulation, window area and orientation, ceiling height, and air leakage. Hill Country homes vary enormously — a 1920s limestone house and a 2015 build with the same footprint have very different loads.

A bigger furnace is not a better furnace. A correct one is.

Consider the System Type Before the Furnace

Before choosing a furnace, it is worth asking whether a furnace is the right equipment at all.

Our cooling season runs roughly seven months and our winters are short and mild. That profile favours a heat pump, which handles both heating and cooling from one system and spends nearly the whole heating season in its efficient range.

A hybrid fuel system pairs a heat pump with a gas furnace and switches automatically by outdoor temperature — often the best fit for homes that already have gas service and want efficiency without giving up furnace heat during a freeze.

If you are replacing an aging air conditioner at the same time, this question is worth real consideration rather than a default.

Efficiency, Honestly Assessed

Efficiency is rated in AFUE. Modern furnaces range from the low eighties to the high nineties, with condensing models at the top.

Here is the local reality: Fredericksburg winters are short, so furnaces here accumulate far fewer runtime hours than in cold climates. That is why they routinely outlast their national average lifespan — and also why there are fewer hours over which to recover an efficiency premium.

Condensing furnaces also require different venting — PVC rather than metal flue, plus a condensate drain — which adds installation cost.

For many Hill Country homes, a good mid-tier furnace is the better value, with the difference spent on duct sealing or insulation, both of which deliver more comfort per dollar in this climate. We will show you the numbers rather than assuming the top tier is right.

Staging and Blower Type

These affect daily comfort more than the efficiency rating does.

Single-stage furnaces fire at full output every time. Two-stage and modulating furnaces run at lower output most of the time, which holds temperature in a much narrower band and cycles less.

The blower matters year-round, because the same blower moves your air conditioning. A variable-speed ECM blower runs longer at lower speed, which removes far more humidity during a Texas summer — and in this climate humidity control is comfort.

If you are only going to spend extra on one upgrade, the variable-speed blower usually delivers more noticeable benefit than a higher AFUE.

Your Ductwork Constrains Everything

A new furnace cannot outperform the duct system it feeds. Undersized returns force the blower against static pressure it was not built for; leaking supply ducts deliver heated air into your attic.

Higher-end equipment is more sensitive to duct problems, not less. We measure static pressure and inspect the ductwork before quoting.

Installation Quality Outweighs Brand

A mid-tier furnace installed correctly outperforms a premium one installed poorly, every time. Sizing, venting, gas pressure, and commissioning are all installation work, and none of it is on the box.

Ask any contractor how they size, whether commissioning is included, and whether permits are in the price.

Details are on our furnace replacement page. Financing is available.

Contact 72 Degrees or call (830) 240-1835.