AAON vs LII: Which Is the Better Buy in 2026?

Same yardstick, side by side (as of September 2026). Valuation lined up like this is most meaningful for two names in the same corner of the market, which these are. Figures are approximate; verify before investing.

Reading it: LII is the cheaper of the two on forward earnings, but cheaper is not the same as better. Pair the valuation with growth (how far the forward P/E sits below the trailing P/E) and risk (beta) before you decide.

The metrics above tell you which is the marginally better business. The bigger risk for most people is not picking the slightly worse stock, it is over-concentrating. AAON and LII share themes, so owning both, or adding either to what you already hold, can quietly push a large share of your portfolio into one bet.

This is the part a generic comparison page cannot answer, because it depends on what you own. Connect your brokerage and Walnut shows your real, combined AAON and LII exposure, flags overlap with your existing positions, and tells you if adding one would tip you past a concentration you are comfortable with, read-only by default, with your login staying at your broker. Walnut is not an investment adviser.

AAON, Inc. engineers and manufactures premium commercial and industrial HVAC equipment, including semi-custom and custom rooftop units, air handlers, energy recovery units, condensing units, water-source heat pumps, and controls. Its 2021 acquisition of BASX and expansion into cleanroom systems and data center thermal management turned a niche rooftop-unit specialist into a supplier of liquid-cooling solutions for AI and cloud data centers, sold under the BASX brand alongside the flagship AAON-branded product line.

Full AAON guide

Lennox International designs, manufactures, and distributes heating, ventilation, air conditioning, and refrigeration (HVACR) equipment across North America under the flagship Lennox brand and related labels. The business runs in two segments: Home Comfort Solutions (residential furnaces, air conditioners, heat pumps, and related equipment sold largely through dealers and distributors) and Building Climate Solutions (commercial rooftop units, controls, and refrigeration for light-commercial customers such as retailers, restaurants, and convenience stores). A large share of demand is replacement rather than new construction, which gives the model a more stable, recurring feel than pure cyclicals, and the company has leaned on manufacturing efficiency, direct-to-dealer distribution, and pricing to expand margins over time.

Full LII guide

Both fit overlapping themes, but they are not interchangeable. The useful comparison is which set of drivers and risks you want exposure to.

• AAON drivers: Data center liquid cooling (BASX); Record backlog and raised guidance.
• LII drivers: Replacement demand and installed base; Regulatory tailwinds and product mix.

A faster-growing, richer-valued name usually swings harder, so it suits a longer horizon and a higher tolerance for volatility; a steadier, more cash-generative business suits a more conservative or income-minded investor. The honest test is which set of risks you could hold through a drawdown: Valuation is the central risk: AAON trades at a rich multiple (trailing P/E well above 70), so any growth disappointment could compress the stock sharply. For LII, lennox trades at a premium mid-20s earnings multiple, so any slowdown in volumes, pricing, or margins can compress the stock quickly.

Growth-minded investors who believe the theme has years to run tend to accept the richer multiple for more upside; value-minded investors lean toward the cheaper forward earnings and steadier profile. Pick AAON if you believe its drivers more; LII if you believe its. Many investors hold both, but since they share themes, that is a concentrated bet, not diversification. Decide deliberately and check overlap. For the full detail, see the AAON and LII guides.

AAON. AAON carries a premium growth valuation, with a trailing P/E well into the double digits and a forward multiple that assumes the data center cooling ramp continues. The record backlog and raised guidance frame the bull case, while the elevated multiple leaves limited margin for error. Gross margin near ~25% reflects ongoing capacity ramp costs.

LII. Lennox reported Q1 2026 revenue of about $1.14 billion (up roughly 6%) and diluted EPS of about $3.35, beating estimates even as operating margin slipped on cost inflation and higher interest expense. Management guided full-year 2026 revenue growth to about 8%, adjusted EPS of roughly $23.50 to $25.00, and free cash flow of $750 to $850 million. With shares around the low-$500s, the trailing multiple sits in the low-to-mid 20s, a premium reflecting the replacement-driven, high-margin model.

Headline figures (approximate, July 2026): AAON shows revenue (ttm) ~$1.6B, q1 2026 revenue ~$497M (+54% YoY), backlog ~$2.13B (record), market cap ~$11B; LII shows revenue (ttm) ~$5.3B, q1 2026 revenue ~$1.14B (up ~6% YoY), q1 2026 diluted eps ~$3.35 (down ~8% YoY), 2026 adjusted eps guidance ~$23.50 to $25.00.

AAON and LII are related but distinct: same themes, different businesses and risks. Neither wins in the abstract; the right pick is whichever thesis you actually believe, sized so you are not over-concentrated in one theme. Walnut can show your combined AAON and LII exposure against your real portfolio. It is not an investment adviser.