Does Your Houston Home Have Enough Panel Capacity?
How to work out whether your Houston home can take an EV charging circuit as it stands, before anyone quotes you a panel upgrade.
By Houston EV Installers
This post is about working out whether you have a problem. If you already know you do and want to understand what fixing it involves, that is a separate question about cost.
Look at the main breaker first
At the top of your panel there is a large breaker with a number on it. Commonly 100, 125, 150 or 200 amps. That is your service rating — the total capacity coming into the house.
Write it down. It is the number everything else is measured against.
Slot count is a different question
A widespread confusion worth clearing up: the number of empty breaker positions in your panel has almost nothing to do with whether you have capacity.
A panel can be physically full while the service has ample headroom. It can equally have empty slots on a service already close to its limit.
Where the panel is full but the service is fine, tandem breakers (where the panel is listed for them) or a subpanel create space without touching the service. That is a much smaller job than a service upgrade, and being told “your panel is full, you need an upgrade” without any further analysis is not an answer.
What your build year suggests
A useful first indicator across the Houston area.
Likely to have room. Post-2000 construction, which covers most of Fulshear, Cypress, Shadow Creek in Pearland, Sienna in Missouri City, and the newer Katy subdivisions. These were built with 200-amp services for households already running heavy air conditioning.
Worth checking carefully. 1980s and 1990s stock — much of Atascocita, the older Sugar Land sections, Kingwood.
Frequently the constraint. Pre-1980 housing. Pasadena, the Klein area of Spring, Jersey Village, older Baytown and Deer Park, Quail Valley in Missouri City. Original 100 and 125-amp services are still in place across these areas.
This is an indicator, not a verdict. A 1975 house that has been rewired has a different answer from one that has not, and a 2005 house with a pool, a workshop and a second HVAC system may have less headroom than its build year suggests.
What has been added since
The thing that most often overturns the build-year guess.
Pool equipment. A second air conditioning system. A workshop or detached garage with its own circuits. An electric range replacing gas. A tankless electric water heater. Each consumed some of the margin the house was built with.
If several of those apply, the assumption that a 200-amp service has room stops being safe.
Why the calculation is the only real answer
A load calculation totals your fixed loads against the service rating using a defined method, and shows what remains.
That produces one of three outcomes: capacity available, capacity available with load management, or a genuine need to grow the service. Those are very different projects, and nothing except the calculation distinguishes them.
It is a small piece of work. Doing it first means you find out which project you are buying before someone quotes you the largest of the three.
The middle answer people are rarely offered
Load management deserves to be known about, because it is frequently the correct answer and it produces the smallest invoice.
The equipment monitors household draw and pauses or throttles charging when the rest of the house is working hard. Your air conditioning and your charger stop competing at six in the evening. Overnight, when the house is quiet, the charger takes full current — which is when it was going to charge anyway.
For a great many Houston homes with modest shortfalls, that is the entire problem solved, without involving the utility.
Before you accept a quote
Ask what the load calculation showed, and ask whether load management was considered and why it was ruled out.
Call (346) 406-1223 and we will run the calculation first.