Choosing the right-sized heat pump for your home isn’t just about matching square footage—it’s about tailoring your system to your lifestyle, location, and comfort goals. A 3-ton heat pump system like the Goodman GLZS4BA3610 with the AMST36CU1300 vertical air handler offers a compelling balance of power and efficiency—but is it right for your home?
This guide explores how heat pump sizing works, what “3 tons” really means, and when a 3-ton system hits the sweet spot—or misses the mark. Whether you’re replacing an old unit or outfitting a new build, here’s everything you need to know.
📏 What Does “3 Ton” Actually Mean?
Let’s clear up a common misunderstanding: heat pump “tonnage” doesn’t refer to weight. It’s a measurement of cooling and heating capacity.
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1 ton = 12,000 BTU/hour
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3 tons = 36,000 BTU/hour
In plain terms, a 3-ton system can remove 36,000 BTUs of heat per hour from your home during cooling season—or deliver that much heat during winter.
✅ Key takeaway: Sizing your system too small means inefficient operation and poor comfort. Sizing it too large leads to short cycling, higher energy bills, and moisture issues.
📍 What Size Heat Pump Do I Need?
Most homeowners are surprised to learn that square footage is just the starting point. While rules of thumb exist, a proper system selection requires analyzing several home-specific variables.
🧮 Rule of Thumb: Square Footage vs. Tonnage (Approximate)
| Home Size (sq ft) | Recommended Tonnage |
|---|---|
| 600 – 1000 | 1.5 tons |
| 1000 – 1300 | 2.0 tons |
| 1300 – 1600 | 2.5 tons |
| 1600 – 1900 | 3.0 tons |
| 1900 – 2200 | 3.5 tons |
| 2200 – 2600 | 4.0 tons |
🚨 But beware: These are rough estimates and don’t account for insulation, climate zone, window orientation, or ceiling height.
🌡️ Climate Zone: A Critical Factor
Where you live affects how much heating and cooling power your home needs. For instance:
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Hot, humid zones (Florida, Texas) demand more cooling, sometimes justifying a 3-ton unit in homes as small as 1400 sq ft.
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Northern climates (Minnesota, New York) might need supplemental electric strips in winter—but smaller AC loads.
📌 Use the DOE’s climate zone map here:
👉 U.S. DOE Climate Zones Map
🧱 Other Key Factors That Affect Sizing
A proper Manual J load calculation (what pros use to size systems) takes into account:
1. Insulation Levels
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R-value of attic, wall, and crawlspace insulation
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Poor insulation means you’ll need more capacity to compensate
2. Window Size and Quality
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Double-pane, Low-E windows reduce cooling loads
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South-facing windows can significantly increase solar gain
3. Ceiling Height
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A 2,000 sq ft home with 10 ft ceilings needs more BTUs than one with 8 ft ceilings
4. Occupancy & Lifestyle
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People = heat. A home with 6 residents will have different needs than one with 2
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Appliances, computers, and even pets generate heat!
5. Ductwork Efficiency
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Leaky or undersized ducts can compromise performance—no matter how well-sized your heat pump is
📎 Read more: Manual J Load Calculations Explained
🛠️ How to Calculate the Right Size
Your HVAC contractor should perform a Manual J calculation using approved software. But to get a ballpark estimate, you can try this formula:
✏️ BTUs Needed = Square Footage x 20-30 (based on insulation and climate)
For example, a 1,800 sq ft home in a temperate zone:
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1,800 x 25 = 45,000 BTU
That equals 3.75 tons—which may push you to a 3.5 or 4-ton unit, especially if your insulation is lacking.
⚠️ Always round up in colder climates and if your windows or attic are under-insulated.
🏠 Ideal Home Profiles for a 3 Ton Heat Pump
✅ Perfect Fit:
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1,600–1,900 sq ft home in temperate climate (Zone 3 or 4)
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Proper insulation (R30+ attic, R13+ walls)
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Energy-efficient windows and doors
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Sealed, insulated ductwork
⚠️ Maybe Too Big:
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Homes under 1,400 sq ft
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Tight building envelope (spray foam, passive house standards)
🚫 Too Small:
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Homes over 2,100 sq ft in humid climates
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Multi-story homes with large sunrooms or cathedral ceilings
🔄 What Happens If You Oversize or Undersize?
❌ Oversized:
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Short cycling = system turns on/off frequently
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Higher energy bills
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Poor humidity control → sticky air
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More wear and tear = reduced lifespan
❌ Undersized:
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Can’t keep up on hot or cold days
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Runs constantly, increasing your power bill
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May never reach setpoint
🧰 How the Goodman 3 Ton System Matches the Profile
The Goodman GLZS4BA3610 paired with the AMST36CU1300 vertical air handler is:
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✅ Rated at 15.2 SEER2, making it 10–15% more efficient than many legacy systems
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✅ Equipped with a multi-speed ECM blower, which adjusts airflow for precision comfort
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✅ Matched with a durable all-aluminum coil that resists corrosion
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✅ Pre-charged with R-410A (with 2025 R-32 compatible models pending)
This system is ideal for medium-sized homes in zones 2–5 that want a dependable, no-frills solution with Goodman’s 10-year warranty coverage.
🔗 Goodman SEER2 Ratings – Goodman Manufacturing
💵 What About Energy Costs?
According to Energy Star, switching from a 10 SEER system to a 15.2 SEER2 heat pump can save 30%+ on cooling bills per year.
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A 3-ton, 15.2 SEER2 unit running 1,200 hours per year may cost ~$650 in cooling electricity per year (depending on kWh rate)
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Higher SEER2 = lower annual operating cost
💡 Pro Tip: Don’t Skip the Load Calc
Even if you’re buying online, don’t skip a Manual J calculation. Many utility companies or local contractors offer low-cost or free load calculations with energy audits.
📎 Home Energy Audit Info – U.S. Department of Energy
🧑🔧 When to Call in the Pros
A licensed HVAC contractor can help:
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Run proper sizing models (Manual J, S, D)
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Inspect your ducts for compatibility
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Handle local permit requirements
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Confirm whether 3-ton equipment is the best fit vs. oversizing/downstaging
Ask them to provide:
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The full load calc summary
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System match documentation (AHRI certificate)
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Efficiency projections
📦 Conclusion: Is a 3 Ton System Right for You?
A 3-ton heat pump is a versatile, popular size that fits many homes in the 1600–1900 sq ft range, assuming standard insulation and climate conditions. When matched with a smart air handler like the AMST36CU1300, the Goodman GLZS4BA3610 system offers efficient, reliable comfort for years to come.
However, HVAC is never one-size-fits-all. Confirm your needs through a proper load calc—not guesswork.
🔗 External References Recap
In the next topic we will read about: What’s New in SEER2? How the Goodman 15.2 SEER2 System Compares to Older Models
