Sizing for Smaller Spaces: 600‑700 sq ft Rooms, Portable ACs, and How

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Hey folks — Mike Sanders here. Today we’re going to dig into something that may seem simple at first glance, but gets surprisingly complex when you push into specifics: how to size an air‑conditioning system for smaller spaces — say around 600 sq ft to 700 sq ft — and how that compares to “full home” systems like the Goodman 3‑Ton bundle. Whether you’re considering a portable AC unit for 600 sq ft, a 700 sq foot portable air conditioner, or you’re wondering if you really need a full‑blown system when you’ve got a smaller space, this is the breakdown you want.

We’re going to cover:

What “600–700 sq ft” really means for AC sizing
How portable AC units perform for that space range
When a central (or large split) system like the Goodman 3‑ton bundle is still relevant — even for smaller spaces
Common mistakes I see in sizing and choosing portable vs full systems
My real‑world advice (yes, Mike Sanders style) for how to make the right choice

By the time we're done, you'll know whether a portable AC for ~600 sq ft makes sense for your use case — or whether you'd be better investing in an entire system such as the Goodman bundle for long‑term comfort and value.

Why 600‑700 sq ft is a Critical “Sweet Spot” for Cooling

Let’s start with the basics. Many homeowners have spaces in this range: a large living room, basement rec room, finished garage, or studio addition that's around 600 sq ft or 700 sq ft. You ask: “What size AC do I need?” and “Can I use a portable unit or do I jump into a big system?”

Here’s how the general sizing logic works:

Portable air‑conditioners are often rated and marketed by “rooms up to X sq ft.” For example, many portable models list “up to 600 sq ft.”
For full‑home or split system air conditioners, tonnage (e.g., 3‑ton) corresponds to BTU capacity (1 ton ≈ 12,000 BTU/h). A 3‑ton unit ≈ 36,000 BTU/h.
For smaller spaces (~600‑700 sq ft), the rule of thumb is often significantly less tonnage — maybe 5,000–14,000 BTU for portable units. (Logan Services A/C, Heat & Plumbing)
The challenge is: the portable units hit that size‑range sweetly, but they have limitations. Whereas when you use a system like the Goodman 3‑ton bundle, you’re well‑oversized for 600‑700 sq ft — unless you have special usage (e.g., you also want that system for the rest of the house).

So this size‑range invites important decision points: portable vs full system, budget vs future proofing, efficiency vs comfort.

How Portable AC Units Stack Up for ~600‑700 sq ft

If you’ve got a room (or connected space) around 600 square feet, you’ll often see marketing like “portable air conditioner for 600 sq ft,” “portable ac units for 600 sq ft,” or “700 sq foot portable air conditioner.” Let’s sift through that.

What the Research Shows

Portable AC units labeled for “501‑700 sq ft” are common. For example, one retailer grouped units under “501‑700 sq ft portable air conditioners” with models meant to cover that range. (Lowe's)
Another example: a portable model rated for “rooms up to 600 sq ft” was described in detail as doing so.
General guidance: portable units may range from “8,000 to 13,500 BTUs = 300 to 600 sq ft” for indoor spaces.

What That Means in Practice

For a room ≈600 sq ft:

If you use a portable model rated for 600 sq ft, you’re likely within the capacity range — assuming moderate insulation, normal ceiling height, and average sun exposure.
You’ll want to check “sizing” carefully: many portable units are sized for ideal conditions (moderate climate, low heat gain). If your room is south‑facing, has lots of windows, or is poorly insulated, you may need more capacity.
Portable units are appealing because they can be moved, don’t require full ductwork, and have lower upfront cost. But they often cost more per BTU, may be less efficient, and might be noisier or have more visible components than a built‑in system.

Limitations & Trade‑Offs

Portable AC units use exhaust hoses (often single‑hose or dual‑hose), meaning you’re venting hot air and possibly drawing air from the room to outside. If the room isn’t well sealed, efficiency drops.
They generally have lower efficiency (higher operational cost) compared to dedicated split or central systems.
If you ever expand your cooled area or want to support multiple rooms, portable units may reach limits quickly.

So yes — for a 600‑700 sq ft room, a portable AC can absolutely make sense. But you need to align expectations: cooling a single room, likely not whole‑house, and plan for optimization (venting, insulation, sealing).

When a “Full System” (Like the Goodman 3‑Ton Bundle) Makes Sense Even for a Smaller Space

Now let’s shift gears and talk about why someone might look at the Goodman 3‑Ton 14.5 SEER2 R‑32 Bundle even if their immediate need is something like a 600‑700 sq ft area. Here’s where the “big system vs small portable” debate gets interesting.

Why Consider a Full System

If your 600‑700 sq ft area is part of a larger home and you anticipate future expansions (finished basement, extra rooms, etc.), investing in a full system prepares you for the future.
If your current equipment is old or failing, and you’d rather upgrade everything once than tinker with multiple smaller units.
Full systems provide better dehumidification, more consistent comfort, quieter operation, and more efficient operation long‑term. For example, the Goodman bundle offers R‑32 refrigerant, matched air handler, and a 14.5 SEER2 rating.
If you have central ductwork already in place (or it’s feasible to add), using that ductwork with a properly sized system yields better distribution across multiple rooms.

Why the Goodman 3‑Ton Bundle Is A Strong Option

A 3‑ton system (36,000 BTU) provides capacity that covers much more than 600‐700 sq ft — typically multiple rooms or full floors. So using it for 600 sq ft might seem overkill unless you’re future‑proofing.
The “bundle” nature means it includes matched condenser + air handler. That means better performance and reliability compared to random replacements.
Using a high‑quality system now avoids incremental fixes later.
A system like the Goodman bundle gives you flexibility: you could cool the 600‑700 sq ft now, expand later, or maintain whole‑house comfort without needing a second system.

But Let’s Be Clear — It Might Be Overkill

If your only goal is cooling a single 600‑700 sq ft room and you have no plans to expand, then a full 3‑ton system might be more than needed. The higher upfront cost may not justify it compared to a well‑sized portable or smaller split unit. That’s why matching capacity to actual need is crucial.

How to Make the Right Decision for Your 600‑700 sq ft Space

Here’s how Mike Sanders recommends you work through the decision:

Step 1: Clarify Your Scope

Is your cooling need strictly 600–700 sq ft (one room, rec area) or is it part of a larger home?
Is the space standalone or integrated with the rest of the house (same ductwork or separate)?
Do you foresee expansion (additional rooms, finishing basement, etc.)?

Step 2: Evaluate Room Conditions

Ceiling height: Are they standard 8 ft or taller? Higher ceilings increase load.
Insulation: How well insulated are the walls, ceiling, windows?
Sun exposure: Does the room have large south or west‑facing windows?
Ventilation/ductwork: Does the room share with the rest of the house or is it independent?

Step 3: Compare Portable vs Full System Costs & Benefits

Portable AC for the room:

Lower upfront cost
Simpler installation
Likely higher operational cost and fewer features
Full system (Goodman bundle or similar):
Higher upfront cost
Better comfort and features
Longer term value, especially if you’ll expand

Step 4: Investigate Long‑Term Value

If you plan to stay in the space for many years or expand, investing in a full system likely pays off.
If your need is short‑term (e.g., rental space, seasonal use), a well‑sized portable may suffice.
Consider lifecycle cost: installation, electricity, maintenance, replacements.

Step 5: Size Appropriately

If you opt for a portable AC for ~600 sq ft: aim for something rated for that space or slightly above (maybe ~10,000‑14,000 BTU) depending on conditions.
If you opt for a full system and your home is larger or you plan expansion: something like the Goodman 3‑Ton bundle is strong — but confirm load calculations.

Helpful sizing and selection resources exist; for example, HVACDirect provides a guide for sizing your air conditioner or heater. (HVAC Direct)

Real‑World Scenario: Cooling a ~650 sq ft Bonus Room

Let’s walk through a realistic scenario where you have a 650 sq ft space (finished bonus room above garage) and you need to decide how to cool it.

Scenario Details

Room size ≈ 650 sq ft
9‑ft ceilings
Two south‑facing windows
Moderate insulation, existing heat gain from garage below
Ductwork currently not tied to main HVAC system

Decision Options

Option A: Portable AC Unit

Choose a portable unit rated for ~650 sq ft (e.g., 12,000‑14,000 BTU)
Lower upfront cost, less installation work
Might have higher operational cost; may be less efficient than a full system
Could be noisy, may require window/hose setup

Option B: Add to Existing Central / Install New System

Tie the room to the main system or install a properly sized mini‑split or full 3‑ton system
Higher upfront cost, more installation required
Better comfort, efficiency, and expansion capability
Long‑term investment

Recommendation (Mike Sanders)

If the room is the only space you care to cool for now and you don’t plan expansion: go with a high‑quality portable AC unit sized for ~650 sq ft.
If you foresee finishing more space or want to avoid dealing with multiple units in the future: invest in a system like the Goodman 3‑Ton bundle (or appropriate size depending on full home load) and integrate the space now.

Why I Keep Bringing Back the Goodman 3‑Ton Bundle

Now you might wonder: “Mike, I came here for a 600‑700 sq ft solution — why do you keep talking about a 3‑ton full home system?” For several reasons:

It’s a great benchmark for capacity, efficiency, and long‑term value. It’s a “real HVAC system” rather than a niche portable.
It helps you understand the ceiling of benefit: if you opt for a full system, you’re investing in long‑term solutions that serve more than just the one room.
It gives homeowners a comparison point: “Would I be better off spending more now on a system that covers more vs. a portable that only covers one room?”
For many homeowners, even if the immediate need is smaller, the “full system” option becomes more cost‑effective when you consider future seasons, resale value, and comfort.

In short: the Goodman bundle defines the premium side of the choice. Portable units define the lower‑cost one‑room side. Your job is choosing where you fall on that spectrum.

Key Mistakes to Avoid (In Portable or Full System Planning)

Here are the most common mistakes I see homeowners making when dealing with smaller‑space cooling or deciding between portable vs full system:

Size by Square Footage Alone Without Considering Other Factors
- Don’t assume 10,000 BTU = “room size number” without checking insulation, windows, heat load, ceiling height.
- The sizing guide from Logan‑Inc emphasizes this. (Logan Services A/C, Heat & Plumbing)
Assuming Portable Was Cheap Upfront Means It’s Cheaper Long‑Term
- Operation may cost more; efficiency may be lower; you might upgrade again soon.
Skipping Installation Quality
- Even a perfect portable unit needs correct venting and placement. A full system needs proper ductwork or design.
Ignoring Future Usage
- If you’re going to expand, finish other spaces, or resell — think bigger now.
Oversizing “Just in Case” Without Load Calculation
- Bigger isn’t always better. Oversized systems can dehumidify poorly, cycle inefficiently, cost more on electric bills.
- The HVAC sizing tool from HVACDirect shows this. (HVAC Direct)

My Final Recommendation (Mike Sanders’ Verdict)

Here’s my summary, straight talk:

If you’re dealing with a dedicated 600–700 sq ft room (bonus room, finished attic, studio) and you don’t plan to add more space, a well‑sized portable AC unit for 600‑700 sq ft is a practical, cost‑effective solution.
But if you own the home and are thinking long term — comfort, resale, multiple rooms — then investing in a full system like the Goodman 3‑Ton bundle (or the correct size for your home) is likely the smarter move.
The key is: match size, consider future, and don’t pick the cheapest unit just because it’s advertised for your square footage.
And above all: get a professional load calculation (Manual J) or at least a thorough assessment. It’s worth the peace of mind.

So if I were advising you today: evaluate your space, check your budget, think about the next 5–10 years, and pick accordingly. For a one‐room portable, make it good. For a whole‐home investment, go for the system.

Tags: Cooling it with mike