OpenClaw 4: Jax and I Team up Against the Furnace

My furnace and AC were original to the house — almost 30 years old. The furnace finally gave up in January, which is the worst possible time and also the most predictable outcome for a nearly three-decade-old HVAC system. I needed replacements fast.

My city has one HVAC company that advertises everywhere, and is in nearly every driveway. I called them, a very nice salesman gave me an enormous quote. I fed it to Jax, asked her to go to work and find additional local HVAC companies. She provided three excellent choices, their phone numbers, websites, history, and any other info she could glean. I called them I got four quotes, ranging from $11,200 to $19,500. Then I did what I would normally do: stared at the spreadsheets, felt confused, and started to pick the one in the middle. Before I could do that, I sent everything to Jax. What came back changed my decision.

The Quote Landscape

Four vendors. Four different combinations of equipment, pricing, and warranty terms. The numbers ranged widely and the warranty language was dense enough that I wasn’t reading it carefully. That’s exactly the kind of thing I will consistently skip — and also exactly the kind of thing that comes back to bite you years later when a $600 labor bill shows up for a “warranty repair.”

Jax read all four quotes in full. She built a comparison matrix. Here’s a simplified version of what she found:

The Warranty Finding That Changed Everything

That labor/parts distinction is buried in the fine print of every quote. Jax flagged it explicitly and compared all four vendors on this specific axis. The upshot: any vendor offering an extended warranty that includes labor is significantly more valuable than one that’s parts-only, even if the parts-only warranty is “10 years from the manufacturer.”

MTB Mechanical was quoting $700 for their extended warranty covering both parts and labor for 10 years. I pushed back a little — asked if there was room to negotiate — and they threw in a media filter and dropped the warranty to $300. So I paid $300 for what’s essentially labor insurance on a $17K system. That’s a very good deal.

“The Trane 10-year warranty covers parts only. Labor costs for an HVAC repair in year 8 can easily run $500–800. The MTB extended warranty at $700 (now $300) covers both — that’s your breakeven at one service call.”

Jax wrote that analysis. I would have looked at “10-year warranty” in the Trane column and checked the box. Not the same thing.

The Financing Math

Both the 18-month and 36-month 0% financing options were available. I assumed I’d take the shorter term — get it paid off faster, less exposure. Jax ran the numbers differently.

With 36-month 0% financing, the full principal stays in my high-yield savings account longer. At current HYSA rates (~5%), that’s approximately $632 in additional interest earned over the difference in term length. You’re essentially getting paid to take the longer loan because the money you’re not paying sits somewhere earning a return.

That’s not a complicated calculation. It’s basic time-value-of-money math. But it’s the kind of thing that feels obvious in hindsight and that I completely hadn’t thought through. I took the 36-month option.

The Equipment Choice

Beyond the warranty and financing, Jax made a recommendation on the equipment itself that I found interesting: the Filtrete 1500 MPR (MERV 12) filter for the Trane S9V2’s variable-speed blower.

The reasoning: the S9V2 runs at variable speeds, which means it cycles more gently and for longer durations than a single-stage furnace. That longer run time makes it more effective at moving air through a higher-resistance filter. A MERV 12 filter on a single-stage system would cause airflow problems. On the S9V2, it works well and actually captures allergens rather than just catching large particles.

We have a baby, a cat, and my wife with cat allergies. Allergen control in the air actually matters to us. Jax knew that from USER.md and factored it into the recommendation without me asking.

What We Ended Up With

• Furnace: Trane S9V2 — 97% AFUE, variable-speed, two-stage gas valve
• AC: Trane XR17 — 17.1 SEER2
• Vendor: MTB Mechanical, “Best” tier package
• Total: $16,839
• Extended warranty: 10-year parts + labor, negotiated to $300 (down from $700), media filter included
• Install date: Wednesday, February 18
• Financing: 36-month 0%
• Filter: Filtrete 1500 MPR (MERV 12)

Arguably a better system, better warranty, for nearly $7,000 less than my first quote.

I’m confident this is the right decision. Not because I’m great at HVAC research — I’m not — but because I had something that actually read the fine print, ran the math, and explained the tradeoffs clearly. That’s the use case I want to highlight here: not “AI is smart,” but “AI is patient and thorough in ways I’m not.”

I had four dense quotes with warranty language, financing terms, equipment specs, and pricing variations. Individually analyzing each one to that depth would have taken me two hours and I still would have missed the labor coverage issue. Jax did it in a few minutes and flagged exactly what mattered.