Geothermal Heat Pump Tonnage: What a 4-Ton Quote Means

The quote on your kitchen table says "4-ton geothermal heat pump." A ton here is a rate of heat transfer — 12,000 Btu per hour, nothing to do with weight — and that one number shapes the size of the equipment, the length of pipe going into your yard, the circuit in your electrical panel, and — partly — the price.

What size your house needs is a different question — a load-calculation question, covered in our guide to how geothermal systems are sized with Manual J. This page assumes the number is already on the table and explains what it commits you to.

What a Ton Actually Measures

A ton is a rate, not a weight. ASHRAE's terminology database defines a ton of refrigeration as a "time rate of cooling equal to 12,000 Btu/h (approximately 3517 W)." That's the whole definition: how fast a machine can move heat, expressed in British thermal units per hour.

So the arithmetic behind the common residential sizes is simple:

The definition is written as a cooling rate — tonnage is a nominal capacity label, and a unit's actual delivered heating and cooling at your operating conditions comes from its performance data, not from the label. And because a ton is a rate, "bigger" means "moves heat faster," not "better." A 5-ton unit attached to a house that only ever needs 3 tons of heat moved is not a safety margin; it's a mismatch. Our sizing guide covers why that mismatch costs you money in both directions.

What One Manufacturer Actually Builds

If a contractor quoted you a 3, 4, or 5-ton unit, that lines up with what's actually on the market. Here is what WaterFurnace currently lists for its residential lineup, taken from its own product comparison page:

• The residential span is 2 to 6 tons. Between them, the four current series cover sizes from 2 tons up to 6 — no series in the lineup sells below or above that span.
• Half-ton sizes appear in WaterFurnace's own catalogs. The 7 Series explicitly starts at 2½ tons, and WaterFurnace's older Envision catalog spelled the steps out directly: "2, 2.5, 3, 3.5, 4, 5, 6 Ton Single Speed." (That is an older R-410A catalog, but it shows the 3.5-ton size has been a published catalog item, not a contractor improvisation.)
• Nothing here goes below 2 tons or above 6. If you've seen searches or quotes for 1-ton or 10-ton units, note that neither appears in these residential product lines.
• The same tonnage comes in different machines. In this one brand alone, a 4-ton unit appears in the 3 Series, in the dual-capacity 5 Series lines, and in the variable-speed 7 Series. Tonnage names the size, not the technology — our brand and model guide walks through those tiers.

These are WaterFurnace's ranges, verified from its current page; we have not checked other manufacturers' current lineups here. Treat 2–6 tons as a well-documented example of what a major residential line covers, not as an industry-wide law.

There Is No Square-Feet-Per-Ton Rule

There is no reliable square-foot number for a 4-ton unit — or any other tonnage — and the check on a tonnage quote is a Manual J load calculation, not division by square footage. That is why this page won't print the table you may have come looking for.

No authority publishes a square-feet-per-ton rule for geothermal. Not the Department of Energy, not ENERGY STAR, not the manufacturer literature cited on this page. We went looking for one specifically, and it does not exist. Any table mapping "2,000 sq ft" to "4 tons" is a guess — the author's, not an authority's.

What the authorities do publish is the method. ENERGY STAR's guidance on heat pump installation says it plainly:

"Make sure your contractor verifies the proper size system for your home using a tool called 'Manual J' – a calculation of the amount of heating and cooling your home requires to keep you warm in the winter and cool in the summer."

— ENERGY STAR, Clean Heating & Cooling

Ask the contractor for the Manual J load calculation behind your quote. A contractor who ran one can hand it over. A contractor who sized your system from square footage alone skipped the published method — and on a system where the equipment and a field of buried pipe are both specified by the ton, a wrong guess is expensive in both directions.

A square-foot table is an appealing thing to publish: it feels like an answer and it is easy to type. But two houses of identical footprint can carry very different heating and cooling loads — which is exactly why the published method measures the house instead of measuring the floor.

Loop Length Per Ton: Why the Numbers Disagree

The published figures for ground-loop sizing are all expressed per ton of capacity — and the two public-sector sources that publish them give different numbers:

Both are right, because each describes a different kind of loop.

The DOE figures cover horizontal loops — pipe laid in trenches — and even within that geometry the range runs from 600 to 1,800 feet per ton depending on region. The NYC DDC figure describes vertical closed loops in heating-dominated buildings, where "the heating dominated vertical closed loops typically require only 300-400 linear feet of pipe per ton." The same NYC document adds that a cooling-dominated vertical loop may need nearly twice that.

• There is no universal feet-per-ton rule. The published figures span 300 to 1,800 feet per ton — a 6× spread — and every number in that span belongs to a specific geometry, climate balance, and region.
• The numbers are not interchangeable. You cannot check a vertical-loop quote against the DOE's horizontal figures, or vice versa. If a loop length in your quote looks wrong compared to something you read, the first thing to check is whether you're comparing the same geometry.
• Pipe length is not bore depth. These figures count linear feet of pipe. How deep vertical bores actually go — and what sets that depth — is its own topic, covered in our geothermal well depth guide.

For a 4-ton system, the published ranges multiply out to anywhere from roughly 1,200–1,600 feet of pipe (vertical, heating-dominated, per NYC DDC) to 2,400–7,200 feet (horizontal, per DOE, depending on region). That spread is not sloppiness — it is why loop design is site work, not table lookup.

Electrical Specs by Size: One Catalog's Real Numbers

Tonnage also shows up in your electrical panel. There is no universal amp requirement per ton — but one manufacturer's published catalog shows how, within its own lineup, the larger models draw more current and call for larger circuits.

The figures below are from WaterFurnace's Envision series catalog (SP1585) — an older, R-410A-era document — for units on 208-230 V single-phase, 60 Hz power:

These are one manufacturer's numbers, from one older product line, at one voltage — not requirements for your system. When your installer starts talking about whether your panel has room for a dedicated 50-amp circuit, this is the kind of table that conversation comes from; the numbers that govern your installation are on your specific unit's spec sheet and nameplate.

What Tonnage Does — and Doesn't — Tell You About Cost

Searches like "4 ton geothermal heat pump price" and "geothermal cost per ton" assume tonnage maps to a price. Tonnage sets the scale of the job without settling the price.

What scales with tonnage: the machine and the ground loop. A larger nominal capacity means a larger heat pump, and — as the DOE and NYC DDC figures above show — the published loop figures are written in feet of pipe per ton. More tons, more machine, more pipe in the ground.

What tonnage doesn't pin down:

• Loop geometry. A heating-dominated vertical loop carries a published figure of 300–400 feet of pipe per ton; horizontal loops run 600–1,800. Two 4-ton systems with different loop designs are two very different digging jobs.
• Equipment tier. As the WaterFurnace lineup shows, the same tonnage ships in several different series — dual-capacity and variable-speed models among them. Same "size," different machines, different prices.
• Region and load balance. Even with the geometry fixed, the figures move: DOE's horizontal range is 600–1,000 feet per ton in the North and 700–1,800 in the South, and NYC DDC's vertical figure nearly doubles when the loop is cooling-dominated instead of heating-dominated.

Comparing per-ton prices across quotes is only meaningful if you know the loop geometry and equipment tier behind each one. If one 4-ton quote is dramatically higher than another, look at those two lines of the proposal before blaming the tonnage. For the full component-by-component breakdown of where the money goes, see our geothermal installation cost guide.

Through the end of 2025, a 30% federal tax credit under IRC §25D applied to residential geothermal, and pricing content published before 2026 may quote figures net of that credit. The credit expired for property placed in service after December 31, 2025 — so check the date on any per-ton number you find, and do not let a pre-2026 "after-credit cost per ton" anchor your budget. (As of August 2026; this is not tax advice — confirm your situation with a tax professional.)

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