The myth that Florida ground is too warm for geothermal

Correcting the belief

Ask around St. Augustine and you’ll hear it: geothermal is for Minnesota, where the ground is warmer than the winter air. Down here the ground is cooler than the summer air, so what’s the point?

That is the point. A geothermal heat pump doesn’t care whether the ground is warmer or cooler than outside; it cares that the ground is a steady temperature, and under St. Johns County it is, in the low 70s a few feet down, every month of the year. In July, a conventional air conditioner has to dump heat into 92-degree air. A ground-source system dumps it into 72-degree earth, which is dramatically easier work. In January, the same ground is a warmer heat source than a 48-degree morning. The system runs with no outdoor fan, no outdoor coil, and no condenser sitting in salt air waiting to corrode.

Florida’s warm, wet soil is actually among the better geothermal environments in the country for cooling-dominated homes. The belief has it exactly backwards.

Repair it, replace the pump or redo the loop: a decision tree

Geothermal systems have been in this county long enough that some early installs are reaching the age where owners ask what to do next. The two halves of the system age at very different rates, and the decision tree follows that.

Start: the system isn’t performing.

• Is the loop holding pressure and flow? Check the flow center gauges and look for air in the loop.
• Yes. The loop is fine. Go to the heat pump branch.
• No. A loop leak or a failed circulating pump. Pumps are a straightforward repair. A loop leak is rare, and locating it is specialized work; we bring in the loop contractor.
• Heat pump branch: how old is the indoor unit?
• Under about twelve years, single fault. Repair it. Compressors, reversing valves, blower motors and boards are all replaceable, and the loop that feeds it is doing most of the work.
• Over fifteen, major fault. Replace the heat pump only. The loop field outlives the equipment by decades; a new indoor unit on an existing, tested loop is the most cost-effective upgrade in HVAC.
• Unknown age, repeated faults. Have us test the loop and the unit together. Repeated compressor trouble sometimes traces to a loop that was undersized for the house at install.
• The house has grown or been renovated. The loop may now be too small for the load. Add loop capacity or supplement with a conventional system for the addition; we’ll model both.

Talk through your system

Equipment we install and service

Geothermal and solar-compatible installs are within Cook’s certifications. For ground-source heat pumps we work with the major manufacturers’ water-source lines and pair them with Lennox air handlers and controls where the design calls for it. Closed horizontal loops suit the large lots of Flagler Estates, Hastings and the rural stretch along SR 13; vertical bores suit the tight lots of Nelmar Terrace, Fullerwood Park and the beaches, where there is no room to trench. We’ll say which fits your property after walking it. [[CONFIRM WITH JERRY]]

On the service side, we maintain and repair existing geothermal systems regardless of who installed them. The annual visit covers the indoor unit much as a conventional heat pump’s would, plus loop pressure, flow rate, antifreeze concentration if the loop uses it, and the circulating pumps.

What the paperwork guarantees

Three warranties overlap on a geothermal install, and it helps to know which is which:

1. The loop. Manufacturer warranties on HDPE loop pipe run for decades. The fusion joints are the loop contractor’s responsibility, and we’ll put the workmanship terms in writing.
2. The heat pump. A parts warranty from the manufacturer, usually with an extended compressor term when the unit is registered, and usually conditional on annual professional maintenance.
3. Our labor. Cook’s stands behind the installation with a satisfaction guarantee. If something we put in isn’t right, the return trip to correct it is ours.

No warranty on earth covers a unit that ran for five years on a dirty filter, so the maintenance visit isn’t optional if you want the paper to mean anything.

Paying for a loop field over time

A geothermal system costs more up front than a conventional heat pump, almost entirely because of the loop. The loop is also the part that lasts the longest and the reason the monthly FPL bill drops. Cook’s puts geothermal on the same monthly installment footing as any other efficient system, and for many St. Augustine households that payment lands near what the old system was costing in extra electricity. The generous federal credit geothermal enjoyed for years lapsed with the 2025 calendar, so it does not enter our math. We don’t quote lender names or rates on this page because both change.

Where geothermal makes the most sense in St. Augustine

• Bayfront and island homes tired of replacing corroded condensers every decade.
• Historic-district properties where the review board limits visible outdoor equipment and a buried loop solves the problem entirely.
• Acreage lots in Flagler Estates, Elkton and Hastings with room for a horizontal field and owners who plan to stay a long time.
• New construction in Palencia and the Nocatee edge, where the loop can go in before the landscaping does.
• Flood-prone streets in Davis Shores, where putting the entire system indoors and above the base flood elevation removes the tide from the equation.

Where it makes less sense: a short-term rental the owner plans to sell in three years, or a small condo lot with no ground to work with. We’ll tell you which category you’re in.