Case Study 13-1: The Rodriguez Townhouse — 100-Amp Service at the Crossroads
Isabel and Miguel Rodriguez have been happy in their 1982 urban townhouse for eight years. Isabel's background as an architect means she thinks carefully about how spaces function, and over the past two years she's been building a mental picture of their home's electrical system — first by reading their electric bills carefully (as described in Chapter 12's case study), then by mapping their panel.
The map revealed a 100-amp service with 24 breaker spaces — 20 occupied, 4 empty. Their calculated load came to approximately 72 amps, which is 72% of service capacity. That felt like reasonable headroom.
Then they had a conversation about what they actually wanted to do to the house.
The Wish List
Miguel had been driving an older gas car, but his company was moving its fleet to EVs and he'd been offered a take-home vehicle. That meant they needed a Level 2 EV charger at home — the 240V kind that provides real overnight charging, not the slow 120V trickle from a regular outlet. Their electrician friend estimated a Level 2 charger circuit at 40 amps dedicated load.
Isabel had been tracking energy costs and was increasingly interested in switching their gas forced-air furnace (due for replacement) to an electric heat pump. A 3-ton heat pump for their townhouse footprint would add about 18 amps at 240V.
They were also considering a bathroom renovation that would add a new circuit for a ventilation fan, heated floor, and additional outlets — roughly one new 20-amp circuit.
And they'd been told, at their last home inspection, that their panel didn't have AFCI breakers on the bedroom circuits — a code deficiency for any new work.
Running the Numbers
Isabel, now comfortable with load calculations from Chapter 13, sat down to work through the math.
Existing calculated load: 72 amps (established from panel mapping and appliance inventory)
New loads: - EV charger (Level 2, 40A): +40A - Heat pump (18A at 240V): +18A - Bathroom circuit (20A at 120V, single-pole): +10A (half of 20A, since it loads one leg)
New total: 72 + 40 + 18 + 10 = 140 amps
Their 100-amp service had a maximum of 100 amps. She was looking at a 40% overrun.
There was also the physical space question. Their panel currently had 4 empty single-pole spaces. A 40A EV charger requires a 2-pole breaker (taking 2 spaces). The heat pump requires another 2-pole breaker (2 spaces). The bathroom circuit needs 1 space. That's 5 spaces needed and 4 available — one short, before even considering that some of the existing single-pole breakers might need to be replaced with AFCI types.
The conclusion was clear: a service upgrade wasn't something they could defer. It was a prerequisite for the improvements they wanted.
Getting Quotes
Isabel called three licensed electricians. She prepared a specific written scope:
"200-amp service upgrade from existing 100-amp service. New 200-amp panel in existing location. All permits and utility coordination included. Following panel replacement: install 40-amp 240V circuit for EV charger in garage, install 18-amp 240V circuit for heat pump (outdoor unit hookup), install one new 20-amp 120V bathroom circuit with GFCI, replace bedroom breakers with AFCI type as required by current code."
The three quotes:
Quote A — $4,200 total: Service upgrade: $2,800. New circuits as described: $1,400. Permit included. "We handle the utility call, typical lead time 2–3 weeks for utility appointment."
Quote B — $3,100 total: Service upgrade: $2,100. New circuits: $1,000. "Permit available at additional cost, approximately $175." No mention of utility coordination in the scope.
Quote C — $3,800 total: Service upgrade: $2,600. New circuits: $1,200. Permit included. "We always pull permits and schedule utility coordination — it's not optional, and any contractor who doesn't is doing you a disservice."
The low bidder (Quote B) gave Isabel pause. "Permit available at additional cost" meant the base quote excluded the permit — that $3,100 would become $3,275 minimum, and the lack of mention of utility coordination suggested the electrician might expect Isabel to handle that herself, or might not be accounting for it at all. She called the Quote B contractor back and asked directly whether the service upgrade price included the utility company coming out to disconnect and reconnect power.
The answer: "Oh, yes, you'd need to arrange that yourself. It's usually free, you just call them." This was technically correct but glossed over a real logistical complication — utility appointments in their urban area often have 2–6 week lead times, and coordinating a licensed electrician's schedule with the utility's availability requires the electrician to manage the timing.
Isabel chose Quote C — $3,800 all-in, permit included, utility coordination handled, contractor who volunteered the permit information without being asked. She felt more confident that nothing would be missed.
The Project
The work took two days.
Day 1: The electrician obtained the permit (already applied for during the quote process), coordinated the utility disconnect appointment, and did the pre-work: running the new service entrance conduit, pulling new service entrance conductors, positioning the new 200-amp panel.
Day 2: The utility came in the morning and disconnected at the meter. The electrician worked through the day: removed the old panel, mounted the new 200-amp panel (a 40-space Square D QO200 load center), connected the service entrance conductors, reconnected all existing circuits to the new panel, installed AFCI breakers on all bedroom circuits, ran the new EV charger circuit, ran the new bathroom circuit, and terminated everything properly. By 3 PM the electrician called the utility for reconnection; power was back on by 5 PM.
The inspection: The local building inspector came the following morning and spent about 20 minutes looking over the work. He noted that the heat pump circuit hadn't been installed yet (correct — the heat pump itself was on backorder). The inspector approved everything else and issued a partial final inspection; the heat pump circuit would get a final inspection when the equipment was installed. This is normal.
What They Learned
Miguel, who'd been skeptical about the cost, said something Isabel found worth writing down: "I kept thinking $3,800 was a lot of money for work that doesn't look like anything. No new room, no new fixture, nothing you can see from outside. But then I thought about what we actually got: we can charge the car, we can add the heat pump, the bedrooms are now protected from arc faults. And we went from a panel that was over capacity to one with 20 open slots. We could add anything for the next 20 years without ever thinking about the service again."
Isabel added the completed permit paperwork to their home's file, photographed the new panel with its fresh circuit directory, and emailed a copy to herself.
She also noted: the inspector's visit had been routine and brief. There were no corrections required. The permit process had been genuinely friction-free. "I don't know why I thought permits were difficult," she said later. "The hard part was picking the contractor. After that the permit process was essentially invisible."
Discussion Questions
- Why was it important that Isabel developed a full scope of work before calling for quotes, rather than just asking "how much for a panel upgrade"?
- The Quote B contractor's "permit available at additional cost" phrasing is a flag. What are the risks of hiring a contractor who treats the permit as optional?
- Isabel's new 200-amp panel has 40 spaces and only approximately 25 occupied. Is this "wasted capacity" or is the extra space valuable?
- Miguel described paying $3,800 for work "that doesn't look like anything." How would you explain to a skeptical homeowner why electrical capacity is worth paying for even when there's nothing visible to show for it?