Who Pays for the Transformer on a New Home’s Electric Service?

For most new single-family homes, the utility owns the transformer, and whether you pay for it depends on one document: your utility’s line extension tariff. Some tariffs leave it out of your bill entirely. Arizona Public Service, for example, excludes the cost of one single-phase transformer when it prices a new home’s extension. Others count the transformer as part of the extension cost and give you a credit against the total: Holy Cross Energy in Colorado applies a $1,000 allowance, and Xcel Energy’s Colorado tariff bills $1,441 per lot in a residential subdivision after its allowance. A few, such as Austin Energy, charge the full estimated cost of the facilities needed to serve you.

This article covers only the transformer question. For distance, poles, free footage and worked budgets for 200 to 1,000 feet, see cost to run power to a property; for how far each tariff builds at no charge, see free power line footage by utility.

The short answer, utility by utility

How each tariff treats the transformer for an ordinary single-phase home. Wording paraphrased from the documents linked; checked September 24, 2026.

Two patterns cover most utilities: the transformer is carved out and you pay for line only, or it is one item in a total extension cost that an allowance offsets. Ask which pattern applies.

How the allowance decides your share

Arizona Public Service: a cap, with the transformer carved out

APS Service Schedule 3 builds extensions for new permanent single-family homes on an allowance. If the total cost of primary, secondary and service is under $10,000 per applicant, you pay nothing for the extension; anything over $10,000 is a non-refundable contribution in aid of construction. Section 3.4 says the cost used for that test excludes the cost of one single-phase transformer. In practice, the transformer does not count against the $10,000 cap for a single home.

The carve-out does not apply everywhere. In an APS “lot sale” development, where a developer sells lots and each buyer builds, the lot purchaser is responsible for the cost of service, which the tariff says may include backbone, transformer and service. In a residential subdivision the developer advances all project costs, with a refundable portion based on a $3,500-per-lot allowance. If you are buying a lot, ask which section of Schedule 3 the lot was developed under. Water and sewer fees raise the same builder-or-buyer question; see who pays tap and impact fees. See Arizona utility connection costs.

Xcel Energy Colorado: transformer inside a per-lot price

Xcel’s Colorado tariff defines on-site distribution extension facilities to include primary lines, feeders, transformers and related equipment inside a residential subdivision. Its worksheet on sheet R228 prices that on-site work at a standard $2,511 per lot, subtracts the $1,070 residential construction allowance, and leaves $1,441 as the customer’s responsibility (advice letter 1800, effective October 1, 2019). The tariff also says Xcel provides and owns the step-down transformer at the point of delivery. You pay toward it through the extension price, but you do not own it.

Holy Cross Energy: transformer counted, $1,000 credit

Holy Cross, a Colorado cooperative, lists transformers among the costs of a line extension, alongside primary and secondary lines, rights of way, metering and tap fees. It then applies a standard construction allowance of $1,000 per qualifying line extension. For underground service, the point of delivery is the pad-mounted transformer’s secondary connectors, which is where the co-op’s ownership ends and yours begins.

Oncor: the 20 kW line

Oncor, a Texas wires company that delivers power for retail electric providers, splits customers by expected demand. For a permanent customer under 20 kW of estimated maximum annual demand, it builds up to 300 feet of overhead single-phase line (primary, secondary and service drop) at no charge, and underground service at no charge if the cost does not exceed that of 300 feet of overhead line. That section lists no separate transformer charge.

At 20 kW or more, or for any three-phase service, the formula changes. The customer’s contribution equals direct cost minus a standard allowance, and the tariff’s direct cost explicitly includes transformers. The allowance for secondary service is $291 per kW of maximum demand. Ask Oncor how it estimated your demand. See Texas utility connection costs.

SRP and Austin Energy: priced per project

Neither SRP nor Austin Energy prints a residential transformer price. SRP’s rules say it will furnish and install the transformation equipment needed to serve you at a standard voltage, and that it may require a contribution in aid of construction whenever it installs facilities to serve a customer. It may compute that contribution from standard unit costs.

Austin Energy’s FY2026-27 fee schedule lists the line extension fee, for facilities to establish new service, at estimated cost. Its Design Criteria Manual adds that in underground residential areas the customer installs the civil work for Austin Energy’s facilities on the property and pays any cost difference between overhead and underground construction. See the Austin tap fee page for the water side.

Pad-mount vs. pole-mount

A pole-mount transformer serves overhead lines; a pad-mount sits in a locked cabinet on a concrete pad and serves underground lines. The tariffs attach different customer duties to each.

• Civil work shifts to you with a pad. Austin Energy requires the customer to install the civil work for its facilities, set pad-mount transformers on concrete pads, and grant an easement. SRP requires the customer to provide trenching, backfill, boring and conduit for underground service laterals, or pay for that work.
• Underground can carry a premium. Austin Energy bills the difference between overhead and underground costs where underground is used. Oncor limits free underground work to the cost of 300 feet of overhead line.
• Clearances and access. SRP requires a clear, dry area three feet around transformer pads. Holy Cross reserves the right to approve every transformer location and can refuse permanent service until the location is acceptable. A pad site that fails those rules can force a redesign.
• Ownership boundary. With a pad, the utility’s ownership often ends at the transformer’s secondary terminals, as it does at Holy Cross. Everything from there to your panel may be yours to trench, install and maintain. On a manufactured home that run usually ends at a meter pedestal; see mobile home utility hookup costs.

When the customer owns the transformer

Homeowners rarely own a transformer. It happens in three situations:

• Primary-voltage service. If you take service at primary voltage, you own the transformers. Xcel’s Colorado tariff says all transformers beyond the primary connection belong to the customer in that case, and Holy Cross’s primary service rate, which is offered to non-residential customers using 500 kW or more, says the consumer provides and maintains transformers beyond the point of delivery. Austin Energy’s primary service is also a commercial option, and the customer owns everything on its side of the point of service.
• Transformers beyond the point of delivery. Xcel’s tariff says the customer provides and owns any transformer needed beyond the point the company designates, for example to serve a distant outbuilding at a different voltage.
• Special types or voltages. Xcel will not provide transformers of special design, at voltages other than its standard distribution voltage, or beyond a single voltage step. If you need one, you buy and maintain it.

What drives the transformer part of the bill

1. Spare capacity nearby. If an existing transformer can serve your load, there may be nothing new to buy.
2. Your declared load. Utilities size transformers from the load form. A larger service, electric heat, or EV charging can move you to a larger unit or, at Oncor, past the 20 kW threshold. Xcel treats transformer capacity requested above what it would normally design as excess facilities, which the customer pays for.
3. Single-phase or three-phase. APS’s carve-out covers one single-phase transformer only. Oncor puts all three-phase service under its direct-cost formula.
4. Development type. A single custom home, a lot-sale development and a subdivision fall under different sections of the same tariff, as APS’s Schedule 3 shows.
5. Overhead or underground. Underground adds pad, conduit and civil work, which several utilities assign to the customer.

Questions to ask your utility

• Which tariff section applies to my project, and does it include the transformer in the extension cost?
• Is an existing transformer being used, or is a new one being set for my service?
• What load did you assume, and would a different panel size change the transformer?
• Where is the point of delivery, and who owns the equipment between it and my meter?

Related guides: utility extension cost, utility trenching cost, cost to bring utilities to land, new construction utility costs, Colorado utility connection costs, and the utility connection cost calculator.

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