Climate Zone Breakdown: Why a 4-Ton System Works in Georgia but Not in

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When you’re shopping for a new air conditioning system, you’ll often see claims like “a 4-ton unit covers up to 2,400 square feet.” Sounds simple, right?

Here’s the catch: that number assumes your home sits in an average climate. But there’s no such thing as average when you compare Savannah, Georgia, to Portland, Maine.

The same house size in two different climates can have wildly different cooling and heating needs — which means the same 4-ton system might be perfect in one place, but a costly mistake in another.

4 Ton 14.5 SEER2 120,000 BTU 80% AFUE Goodman Upflow Air Conditioner System with Models GLXS4BA4810, CAPTA6030D3, GR9S801205DN

Jake from The Furnace Outlet is here to explain how climate zones change HVAC sizing math — and why understanding your zone is the difference between year-round comfort and wasted energy.

🌎 1. The Climate Factor — The Missing Link in System Sizing

Most homeowners (and plenty of contractors) size systems based on square footage alone. But BTUs per square foot depend heavily on your region’s weather

Here’s the science behind it:

Hotter climates experience higher sensible loads — the heat your AC must remove to cool the air.
Humid climates add latent load — the moisture your AC must wring out to keep the air comfortable.
Cooler climates have smaller cooling loads but heavier heating demands.

That means a 4-ton air conditioner rated for 2,400 sq ft in Atlanta might only need 3 tons in Augusta, Maine.

Jake says:

“Sizing isn’t just about square footage. It’s about how your home fights the climate it lives in.”

👉 Reference: Energy.gov – Central Air Conditioning Sizing Guide

☀️ 2. How Cooling Loads Change by Region

Let’s look at how much heat (and humidity) a home gains in different regions. HVAC pros measure this as BTUs per square foot — or how many British Thermal Units your AC must remove to maintain comfort.

Region	Typical Summer Temp	Humidity Level	Recommended BTU per sq ft	Typical System for 2,400 sq ft
Georgia	95°F	Very High	25–30 BTU	4.0 tons
Tennessee	90°F	High	22–25 BTU	3.5–4.0 tons
Pennsylvania	85°F	Moderate	20–22 BTU	3.0–3.5 tons
Maine	80°F	Low	15–18 BTU	2.5–3.0 tons

So if your home is the same size, your climate zone may swing your cooling needs by 12,000–18,000 BTUs — or an entire ton of system capacity.

Jake explains:

“In the South, your AC fights both heat and moisture. Up North, it’s mostly about dry heat a few months a year.”

👉 See region-specific recommendations: AC Direct – HVAC Sizing by Region

💧 3. Why Humidity Changes the Math

Temperature tells only half the story. The real hidden enemy in southern states is humidity.

When air holds more moisture, your AC has to work harder to remove it — converting warm, damp air into cooler, drier air. That process eats up capacity known as the latent load.

Jake’s rule of thumb:

Each 10% rise in humidity can add 5–10% more cooling load.
A humid 2,400 sq ft home in Georgia might “feel” like a 2,700 sq ft load to your AC.

That’s why a 4-ton variable-speed system, like the Goodman GLXS4BA4810, is ideal in those climates. It runs slower for humidity control and ramps up for peak heat.

In Maine, however, that same 4-ton system would cool the house so quickly that humidity removal would stop early, leaving air damp and clammy.

👉 Learn how humidity affects comfort from Lennox – How Humidity Affects Comfort

❄️ 4. Heating vs. Cooling — The Dual-Sizing Dilemma

Homes in Maine spend far more energy heating than cooling. That changes your system balance.

In Georgia, where winter lows hover around 40°F, you can pair a 4-ton AC with an 80,000–100,000 BTU furnace comfortably.

In Maine, where winters hit 0°F, the same home might need a 100,000–120,000 BTU furnace but only 3 tons of cooling.

Jake’s advice:

“In the South, size for cooling first. In the North, heating rules the equation.”

For hybrid systems like Goodman’s 4-ton R-32 paired with a 120k furnace, this dual balance ensures each side of the system pulls its weight.

🧮 5. Using the DOE Climate Zone Map

The U.S. Department of Energy divides the country into seven climate zones based on temperature, humidity, and seasonal averages.

Zone	Example States	Cooling BTU/sq ft	Heating BTU/sq ft
1–2	FL, TX, GA	25–30	20–25
3–4	TN, NC, VA	22–25	25–35
5–6	PA, NY, ME	15–20	40–50

👉 Explore your region here: DOE – Building America Climate Zones

Jake uses this map when helping customers:

“Once I know your zone, your insulation level, and your square footage — I can tell within a half-ton what system you really need.”

🧱 6. Insulation, Windows, and Building Design

Homes aren’t created equal — insulation and window layout can change your load as much as the weather outside.

Maine homes typically feature tight envelopes, double-pane windows, and attic insulation of R-49 or higher.
Georgia homes often have open floor plans, more windows, and lighter insulation.

So while both houses might be 2,400 sq ft, one keeps heat out naturally, and the other needs mechanical help.

Jake explains:

“Insulation is your first line of defense. The better your house holds temperature, the less tonnage you need.”

📊 7. Real-World Comparison: Georgia vs. Maine

Let’s break down two identical homes — same size, different climates.

Home A – Atlanta, GA

2,400 sq ft, 9-ft ceilings, standard insulation
Outdoor summer highs: 95°F, humidity 70%
Cooling load: ~60,000 BTU
Recommended: 4.0 tons
Furnace: 80–100k BTU

Result: Long cooling season, heavy humidity — 4-ton system runs smooth, dehumidifies well.

Home B – Portland, ME

2,400 sq ft, 8-ft ceilings, upgraded insulation
Outdoor summer highs: 80°F, humidity 40%
Cooling load: ~42,000 BTU
Recommended: 3.0–3.5 tons
Furnace: 100–120k BTU

Result: Short cooling season, lower load — 4-ton system would short cycle, leaving air sticky and bills higher.

Jake points out that both homes are identical in size but require 30% different cooling capacity.

⚙️ 8. Why SEER2 Ratings Vary by Region

SEER2, the new national standard for cooling efficiency, measures performance under realistic duct pressure and 95°F outdoor temps.

But not every state runs at those conditions. In fact:

Georgia homes often operate at or near 95°F for months.
Maine homes may see that only a few days a year.

That means a 14.5 SEER2 Goodman system in Maine effectively performs like a 15–16 SEER2 system in practice — because it runs fewer full-load hours.

In contrast, the same unit in Georgia faces heavier demand, operating closer to its limit most of the year.

Jake notes:

“Efficiency ratings are national averages — your real SEER2 depends on your climate zone.”

🔋 9. Balancing Year-Round Comfort

A 4-ton R-32 system shines in humid southern climates where dehumidification and long run times are essential.

But in northern climates, those same systems can short-cycle — cooling the home so quickly that humidity control fails.

Jake often recommends variable-speed systems or two-stage compressors for border states like Tennessee, Pennsylvania, or Virginia, where both heating and cooling seasons matter equally.

“You want your system to breathe with your weather, not fight against it.”

🧰 10. How to Calculate Sizing Using Climate Zones

Jake’s DIY method for climate-adjusted sizing:

1️⃣ Find your climate zone using the DOE map.
2️⃣ Measure your home’s conditioned square footage.
3️⃣ Apply BTU-per-square-foot factor from your zone:

Zone 1–2: 25–30 BTU
Zone 3–4: 20–25 BTU
Zone 5–6: 15–20 BTU
4️⃣ Multiply and convert to tons:
Example: 2,400 sq ft × 25 BTU = 60,000 BTU ÷ 12,000 = 5 tons (Zone 2)
Example: 2,400 sq ft × 17 BTU = 40,800 BTU ÷ 12,000 = 3.4 tons (Zone 6)
5️⃣ Adjust ±10% for insulation and window exposure.

👉 Double-check your results with the AC Direct Load Calculator

💵 11. Cost and Efficiency Impacts of Wrong Sizing

Oversizing and undersizing both cost money, just in different ways:

Oversized in Maine:
- Higher upfront cost (+$800–$1,000)
- Shorter runtime → humidity problems
- More cycling → faster wear on parts
Undersized in Georgia:
- Constant runtime → higher power bills
- Warmer indoor temps under peak heat
- Reduced SEER2 efficiency

Jake says:

“A well-sized 3.5-ton in Maine will outperform a 4-ton every time — comfort beats horsepower.”

🧩 12. Why Builders Often Oversize (and Why You Shouldn’t)

Many older homes were equipped with oversized units because construction standards were looser — low insulation, single-pane windows, and leaky ducts.

But modern homes are much tighter, meaning older “rules of thumb” overestimate loads by 20–30%.

Jake explains:

“If your home’s been updated since the 1990s, chances are your new system should be smaller than your old one.”

🔧 13. Climate and Duct Design Go Hand-in-Hand

Airflow requirements differ by climate too.

In humid regions, slower airflow helps dehumidify air longer.
In dry regions, faster airflow cools quickly without condensation.

So even if your tonnage is right, duct size and speed must match your climate’s needs.

Jake’s pro tip:

“In Georgia, aim for 350 CFM per ton; in Maine, 400–420. That’s the difference between crisp and clammy air.”

🧠 14. R-32’s Role in Climate Efficiency

Because R-32 refrigerant transfers heat more effectively than R-410A, it amplifies climate differences.
A 4-ton R-32 condenser can actually cool up to 10% more efficiently — great for southern climates, but too aggressive for short cooling seasons up north.

👉 Learn more: Daikin – R-32 Refrigerant Overview

Jake says: