Geothermal For A Small Apartment Building Or Duplex In Oklahoma

Landlords across Oklahoma ask me a version of the same question: for a duplex or small apartment building, do I drill one loop field for the whole property, or does every unit get its own system. I have 47 years in HVAC and 15+ years running my own shop in Kingfisher, and geothermal is where I’ve put my real attention. It’s IGSHPA accredited work, and my license covers me statewide, even though my daily service calls stay inside Kingfisher, Canadian, Oklahoma, Garfield, Major, Logan and Blaine counties. Here’s how I think through a multi-unit job, including the one real DOE case study worth knowing.

One Shared Loop Field, Or A System Per Unit

There are two ways to build this: one shared ground loop field feeding a separate water source heat pump in every unit, or a fully separate system per unit, its own loop and heat pump, nothing shared. The easy assumption is that sharing the field always drills cheaper. I won’t tell you that. The DOE project below found the opposite, and drilling cost turns on your tonnage, your soil, and how the bores lay out. What reliably differs is failure containment.

Shared Loop Field	Separate System Per Unit
One loop field for the whole property	A separate loop field for every unit
Sized against the property’s combined tonnage	Sized unit by unit
A problem in the field can reach more than one unit	A problem stays with that unit

What The DOE Autumn Gardens Case Study Actually Shows

The U.S. Department of Energy documented an apartment property that faced this decision. Autumn Gardens is a senior apartment complex in Lockport, New York, owned by the City of Lockport Housing Authority. DOE reports the authority chose several separate closed loop systems, one for each building, over a single shared field. DOE’s stated reason was reliability: because each building has its own system, if one fails the others aren’t impacted. DOE also reports the separate design ran cheaper to operate, and its loop field cheaper to install, on a smaller footprint with less piping.

Read the money side carefully before you borrow it. The conversion was paid for with accumulated federal housing capital grant money plus a state energy authority rebate, and the property is master metered, so the housing authority pays the utility bills itself. That’s why the savings DOE credits to the project landed with the owner, who was the ratepayer. If your tenants pay their own power, you can’t move that result onto your building without changing who holds the meter. What Autumn Gardens settles is the design question: DOE’s engineers went with separate systems to keep one failure from taking down the whole property.

Metering And How Each Tenant Gets Billed

Here’s the part most owners don’t expect. A geothermal system pulls power in three places, not one: the compressor in each unit’s heat pump, the blower moving air through that unit, and the pump circulating fluid through the ground loop. On a fully separate system, that pump sits on the same meter as the rest of that unit. On a shared field it’s a common load, like a hallway light, so decide whether it goes on a house meter you pay or into rent. The heat pumps themselves can be metered individually either way, so a tenant who runs the thermostat at 65 in July pays for it.

The other option is a master meter, one account for the whole building, with you paying and folding it into rent. A study in The Energy Journal found occupants who pay their own utility bills are measurably more likely to turn the thermostat down overnight. That’s the split incentive: whoever isn’t paying the bill has less reason to run efficiently, and a tenant who doesn’t own the equipment can’t capture an upgrade’s value. Individual meters keep that incentive pointed right. A master meter is simpler bookkeeping, but you absorb the swings.

What A Loop Actually Costs For A Multi-Unit Property

I price ground loops at roughly $3,000 per ton, with about 200 bore feet of drilling per ton. A driller bills for bore feet, the actual depth drilled, not the feet of pipe fed down the hole, so those aren’t the same number when comparing quotes. A shared field gets sized against the property’s combined tonnage, separate fields one unit at a time. Which uses your lot better depends on the property and the drilling conditions. I bring in a driller I trust before anybody promises you a layout. An undersized loop is the most common reason a system underperforms. Every new system gets a free estimate first, so I size the loop against your real tonnage before I hand you a number.

Oklahoma Utility Rebates: OMPA And Alfalfa Electric

On a municipal electric account in Kingfisher, Okeene, or Watonga, OMPA pays up to $800 per ton toward a geothermal install, a cap, not a guarantee, and it requires a desuperheater. In Garfield or Major county on Alfalfa Electric Cooperative, the numbers go the other direction: $1,050 per ton for ground source against $150 per ton for air source. What I don’t have in writing from either utility is who they pay on a rental, the account holder or the owner. Confirm the eligible applicant with them before you settle your metering plan, and don’t budget around rebate money until they say it’s yours.

The Federal Tax Credit Picture For A Rental Property

The federal residential geothermal tax credit, 25D, has expired. I won’t tell you otherwise. Commercial geothermal property falls under a different part of the tax code, Section 48, not Section 48E, with its own rules. Whether your building counts as residential or commercial for tax purposes is a question for a CPA, not something I’ll guess at on a service call. Check current IRS and ENERGY STAR guidance before you build your numbers around a credit.

What A Visit Costs And Keeping Multiple Doors Running

A geothermal diagnostic on a duplex or small residential rental runs $348 flat, any hour, no credit and no refund. It’s a full performance check: loop pressure, refrigerant charge, the desuperheater, controls, and the heat exchanger, with a written report before I leave. A commercial classified property, light commercial up to 15 tons, runs a $389 flat diagnostic, day or night. There’s always a dispatch fee and always a diagnostic fee, I don’t waive either one. A brand new system always gets a free estimate.

For an owner running several units, I offer maintenance agreements that scale with the property, from one seasonal visit up to full year coverage with filter changes and priority scheduling. A job like this can be financed. Call and I’ll walk you through it.

Frequently Asked Questions

Do I need a separate loop for every apartment, or can they share one?

Either works. A shared loop field can feed a separate heat pump in each unit, or each unit can get its own complete system. DOE’s Autumn Gardens project went with separate systems building by building, for reliability. I size it to your lot and risk tolerance.

Who pays the electric bill on a geothermal apartment building?

Whoever is on the meter. Each unit’s heat pump can be individually metered either way, but on a shared loop field the circulating pump is a common load, so decide up front whether it lands on a house meter you pay.

Is there a real example of geothermal working on an apartment building?

Yes. DOE documented Autumn Gardens, a senior apartment complex in Lockport, New York, that cut its energy costs with geothermal. It’s a bigger, publicly owned, master metered property, and the owner pays the utility bills, so treat it as a design lesson, not an investment template.

How much loop do I need for a fourplex?

Roughly $3,000 per ton and about 200 bore feet per ton, sized to your real combined tonnage. Every new system gets a free estimate before anything gets drilled.

Can I get a tax credit for adding geothermal to my rental property?

The federal residential credit, 25D, has expired. Commercial geothermal falls under Section 48, not Section 48E. Talk to a CPA about your ownership structure first.

If one heat pump breaks, does the whole building lose heat?

Only if it’s built that way. A shared loop with separate heat pumps already isolates most failures to one unit. Separate systems isolate it further, which is why DOE built Autumn Gardens as several systems, one per building.

Are there rebates in Oklahoma for adding geothermal to a rental?

On a municipal account in Kingfisher, Okeene, or Watonga, OMPA pays up to $800 per ton with a desuperheater required, a cap not a guarantee. Garfield and Major county customers on Alfalfa Electric Cooperative see $1,050 per ton ground source versus $150 per ton air source. Confirm with the utility who the eligible applicant is before you apply.

I’ve built my business in Kingfisher on geothermal work most shops won’t take on, backed by a Master HVAC license, NATE certification, and BBB A+ standing for 11 years, with 4.8 stars and 300+ Google reviews behind it. If you’re weighing a shared loop against separate systems anywhere in Oklahoma, call 405-375-4822.