Most DFW homes do not need 400 amps. It makes sense when a load calculation shows several large loads arriving at once: EV charging, a heat pump with electric backup heat, a pool or a shop. Our published range for 200 A to 400 A is $4,500–$7,500.
Most homes in Dallas-Fort Worth do not need 400-amp service, and a 200-amp service is enough for a typical house. A 400-amp service makes sense when a load calculation shows the house adding several large loads at once, such as EV charging, a heat pump with electric backup heat, a pool or a shop. Three parties are involved: your electrician builds the new service, the city permits and inspects it, and Oncor handles the meter and the disconnect and reconnect. Our published range for a 200 A to 400 A upgrade is $4,500–$7,500.
When does a house actually need 400 amps?
A load calculation decides it, not a rule of thumb. The National Electrical Code's load calculation (Article 220) adds up the house's general lighting and receptacle load, its appliances and its heating and cooling, then applies the code's demand factors. If the total with the new equipment is near or over the rating of the existing 200-amp service, you can manage the load, upgrade the service, or both.
The loads that push DFW homes past 200 amps draw a lot of power for hours at a time:
- EV charging. A Tesla Wall Connector on a 60-amp circuit draws 48 amps continuously, and a second EV doubles that (see our EV charger cost guide).
- Heat pumps with electric resistance backup heat. On the coldest mornings, the backup heat strips are often the largest single load in the house.
- Electric tankless water heaters, which can need several large circuits of their own.
- Pools, spas, and detached shops or casitas with their own subpanel.
- Switching from gas to electric for cooking, drying and water heating.
A standby generator does not add load to the utility service. It affects the transfer switch: a transfer switch at the service entrance has to be rated for that service. If a 400-amp upgrade is likely, plan it before the generator, not after. The Cummins units we install cover most 2,000–3,500 sq ft homes with the 17 kW RS17A or 20 kW RS20A air-cooled models. Our generator cost guide has the installed prices.
Is there a cheaper option than 400 amps?
Sometimes. An EV load management device pauses charging when the rest of the house nears its limit, and some chargers can split one circuit between two cars. Charging overnight, when the air conditioner is not at full load, also helps a borderline calculation. We run the calculation first and tell you which side of the line you are on. We will not sell a 400-amp upgrade to a house that does not need one.
What does Oncor do, and what does the electrician do?
| Part of the job | Who |
|---|---|
| Load calculation and the decision to upgrade | Electrician |
| City electrical permit | Electrician |
| New meter base, service entrance conductors, mast or conduit | Electrician |
| New panel or panels, grounding and bonding | Electrician |
| Disconnecting the service so the work can be done safely | Oncor |
| The meter itself, set on the new meter base | Oncor |
| Any change to the service drop, underground line or transformer | Oncor |
| Inspecting the new service | City inspector |
| Reconnecting power | Oncor |
In practice, the electrician coordinates the job. We pull the permit, request the disconnect and reconnect, build the new service to Oncor's metering requirements, and schedule the inspection. Oncor decides whether its own equipment, meaning the wires to your house and the transformer that feeds them, has to change for a larger service. That decision and its timing are Oncor's, and they are the biggest variable in how quickly a 400-amp upgrade finishes.
Most residential 400-amp services are built as two 200-amp panels fed from one larger meter base. That also gives you more breaker spaces, so the panel does not fill up again.
Do I need a permit and inspection for a service upgrade?
Yes. Service upgrades are permitted and inspected work in the DFW cities we serve, and the licensed electrical contractor pulls the permit. The edition of the National Electrical Code the inspector enforces depends on the city. The Texas Commission of Licensing and Regulation adopted the 2026 NEC as the state electrical code, effective September 1, 2026 (TDLR rule adoption notice, September 2026). Grand Prairie's published adoption notice lists the 2023 NEC, adopted December 12, 2023, and Mansfield's building codes page lists the 2023 NEC, adopted in 2024. We build to whatever the city enforces.
One common confusion: Texas Senate Bill 1202 (89th Legislature), effective September 1, 2025, lets a licensed master electrician or electrical inspector review and inspect home backup power installations, such as generators and battery systems, in place of the city. Mansfield's guidance on the law says it does not cover electrical service or panel upgrades. A 400-amp service upgrade still goes through the city's normal permit and inspection, even when a generator is part of the same project.
What does a 200 to 400 amp upgrade cost in DFW?
Our published range is $4,500–$7,500, from the 2025 figures in our Federal Pacific replacement guide. The same guide lists two separate items for jobs that need them: $400–$900 for a meter base and $350–$700 for grounding upgrades. The written quote shows what is and is not included before any work starts.
What moves a job within that range:
- Where the meter and panel are, and whether the panel has to move
- Overhead service with a mast, or underground service
- One 400-amp panel, or two 200-amp panels
- How many existing circuits have to be reconnected or extended to reach the new panels
- Whether Oncor has to change anything on its side, which mostly affects the schedule
Financing is available on larger projects such as service upgrades (see financing options). If you are not sure you are at the limit yet, our list of signs a panel needs upgrading is a good place to start.
How long does a 400-amp upgrade take?
On site, a 400-amp upgrade usually takes one to two days, with the power off during the changeover. The time around it varies by city: permit issuance, Oncor scheduling, the inspection, and whether Oncor has to change anything on its side. We give you the sequence in writing with the quote.
Adding an EV, a heat pump or a generator?
Load calculation first, then a written flat-rate quote. Same-day visits, 7 AM to 7 PM weekdays. TECL #40628.
400-amp service questions
Only if a load calculation says so. Most Dallas-Fort Worth homes run well on 200-amp service. Houses that need 400 amps are adding several large loads at once, such as one or two EV chargers, a heat pump with electric backup heat, a pool or a shop. Sometimes an EV load management device keeps a borderline house on 200 amps.
Oncor disconnects the service so the work can be done safely, supplies and sets the meter, and reconnects power. It also decides whether its own equipment, the wires to the house and the transformer, needs to change for a larger service. The electrician handles the permit, meter base, service entrance conductors, panels, grounding and the city inspection.
Clements Electric's published range for a 200-amp to 400-amp upgrade is $4,500–$7,500. Meter base work ($400–$900) and grounding upgrades ($350–$700) are listed separately for jobs that need them. Every job gets a written flat-rate quote after an on-site look.
Not usually. A standby generator does not add load to the utility service. A transfer switch at the service entrance has to be rated for that service, so if a 400-amp upgrade is likely, do it before the generator. Cummins 17 kW and 20 kW air-cooled units cover most 2,000–3,500 sq ft DFW homes.
No. SB 1202, effective September 1, 2025, allows third-party review and inspection of home backup power installations such as generators and battery systems. The City of Mansfield's guidance on the law says it does not cover electrical service or panel upgrades, so those still go through the city's normal permit and inspection.
