By Alexandr Godonoaga, owner of Cob Services LLC. Illinois electrical contractor license #26-00032356. Over 10 years wiring homes in Naperville and the western suburbs.
The call usually comes on a Tuesday. The heat pump is being installed Thursday. The HVAC crew is booked, the equipment is already sitting in somebody’s warehouse, and nobody has looked inside the electrical panel yet.
Sometimes it’s fine. The panel has room, the service is 200 amps, and we run the circuit and the disconnect in a morning. Other times we open the cover and find a full 100-amp panel in a 1970s ranch with an EV charger already on it, and the honest answer is that the equipment on the truck cannot be energized on Thursday.
That conversation is much easier to have three weeks earlier. Here’s what to check before your HVAC contractor orders anything.
The nameplate is the spec, not the tonnage
Every heat pump has a data plate on the outdoor unit with two numbers on it that decide the whole electrical scope.
Minimum Circuit Ampacity (MCA) tells us how big the conductors have to be. Maximum Overcurrent Protection (MOCP) tells us the largest breaker allowed to protect it. They are not the same number and they don’t behave the way people expect. A unit might list an MCA of 24.5 amps and an MOCP of 40 amps. That doesn’t mean you get to run a 40-amp circuit on small wire, and it doesn’t mean 24.5 rounds up to 30 and you’re done.
If someone quotes your heat pump circuit off the tonnage alone, they’re guessing. Two three-ton units from different manufacturers can want meaningfully different circuits. We ask for the spec sheet, and if the equipment hasn’t been picked yet, we ask for the model numbers your HVAC contractor is considering and price the electrical for each one.
The backup heat is the load that surprises people
The outdoor unit is the part everyone talks about. The indoor side is where the load actually lives.
If your system uses electric resistance strips for backup heat, those strips get their own feed and they are large. A 10 kW strip package pulls roughly 42 amps at 240 volts on its own, before you count the outdoor unit, the air handler blower, or anything else in the house. Some installs use 15 or 20 kW. At that point you are adding something close to a second EV charger to a house that was never sized for one.
Dual fuel changes the math completely. Plenty of Naperville homes keep the existing gas furnace as the backup stage and let the heat pump handle everything above the changeover temperature. Nicor delivers the gas, the furnace does the cold snaps, and the electrical scope drops to the outdoor unit plus the air handler. If you’re deciding between all-electric and dual fuel and your panel is tight, that decision is partly an electrical decision. Ask your HVAC contractor to price both and send us the specs for each.
The disconnect, and where the inspector expects to see it
Under the 2023 NEC, which is the code Naperville enforces, the outdoor unit needs a disconnecting means within sight of it and readily accessible. In practice that means a weatherproof pull-out or fused disconnect mounted on the wall near the condenser, not around the corner, not inside the house, not behind the unit where you’d have to reach past a running fan to get to it.
Then there’s the whip: the short run of liquidtight conduit from the disconnect to the unit. On a clean install it’s a few feet. On a house where the panel is on the opposite side from where the equipment is going, the conductor run between the panel and the disconnect is where the cost quietly lives, the same way it does on a garage-to-driveway EV charger run.
One more thing worth knowing. The 2023 NEC requires GFCI protection on outdoor outlets serving this kind of equipment at a dwelling. Some heat pump models have a documented history of nuisance tripping on GFCI protection, and it is much better to find that out during the install than in February at two in the morning. We check the manufacturer’s guidance before we energize.
The load calculation, and what happens if it comes back short
Before any of the above matters, somebody has to answer whether your service can carry the new load at all. That’s a load calculation, not an opinion, and it accounts for the square footage, the existing heating and cooling equipment, the range, the dryer, the water heater, any EV charging, and then the heat pump on top.
Most Naperville houses built before the mid-1990s came with 100-amp service. That was generous in 1978. It gets tight fast once a house has central air, a finished basement, a home office, an induction range, or a car in the garage that charges overnight. We wrote about houses that were sized for a much smaller electrical life and this is the most common version of that problem we see now.
If the calculation comes back short, you have a few real options and one fake one.
The fake one is installing it anyway and hoping. That’s how you end up with a main breaker that trips on the coldest night of the year, which is exactly when the strips and the furnace fan and everything else run at once.
The real options are a service upgrade to 200 amps, a sub-panel if the issue is available breaker spaces rather than total capacity, or changing the equipment so it fits the service you have. That last one is underrated. Going dual fuel, or dropping from a 15 kW strip package to 10 kW, sometimes keeps a perfectly good 100-amp service in play. If you want to sanity check your own panel before you call anyone, our guide to what size panel a Naperville home actually needswalks through the same questions we ask, and the panel assessment we use for EV charger customers applies almost word for word to a heat pump. If it turns out you need extra capacity for other reasons too, the sub-panel versus service upgrade breakdown covers how we choose between them.
If your lights already dip when the AC compressor starts, take that as a hint. Adding a heat pump to that house without looking at the service is asking for a repeat performance in January.
Naperville is not ComEd territory, and it matters here
This trips up contractors from outside the city constantly.
Naperville owns and operates its own municipal electric utility. It has since 1899, and it serves roughly 60,000 meters inside the city. If your heat pump project ends up needing a service upgrade, the meter pull, the service drop, and the equipment approval all go through Naperville Electric, not ComEd. ComEd’s rebate and rate programs do not apply to an address inside city limits.
There’s a practical consequence for your metering equipment too. On projects that involve the service entrance, the city’s electric utility wants to approve the metering equipment before the contractor orders it. Finding that out after the parts are on site adds days you didn’t budget.
If an electrician tells you they’ll “call ComEd to schedule the disconnect” for your Naperville house, they have not done a service upgrade here. That’s a reasonable question to ask on the phone before you hire anyone.
The permit, and who’s allowed to pull it
A permit is required before any electrical work inside Naperville city limits, and the work has to be performed by a state-licensed electrical contractor who is also registered with the City of Naperville. That registration is separate from the Illinois license, and plenty of otherwise legitimate contractors from neighboring towns don’t have it. Applications go through the city’s Civic Access portal, and the City of Naperville’s electrical permit page lays out the requirements.
Two details worth insisting on. The permit should be pulled in the contractor’s name, not yours. A contractor who asks the homeowner to pull the permit is moving liability onto you. And the electrical permit is separate from whatever your HVAC contractor files for the mechanical work, so somebody needs to own it. On our jobs, that’s us. If you want the general picture on when permits are required, we covered electrical permits for Illinois homeowners separately.
Sequencing, so nobody stands around
Heat pump installs go badly when the two trades show up in the wrong order or on the same morning without a plan.
What works: we run the dedicated circuit and set the disconnect ahead of the mechanical install, with the whip left ready. The HVAC crew sets the equipment and makes their connections. We come back to terminate and verify. If a service upgrade is part of the job, that happens first and on its own schedule, because it involves the utility and it is not something to attempt on installation day.
Send your HVAC contractor’s spec sheet to us as soon as you have it. We can size the circuit, run the load calculation, and tell you whether the panel takes it before anyone orders equipment. That single step prevents most of the bad Tuesdays.
Questions we get on heat pump installs
Can my 100-amp service handle a heat pump? Sometimes. It depends on the unit’s MCA, whether you’re using electric backup heat or a gas furnace, and what else is already on the service. A dual fuel system in a modest house often fits. An all-electric system with 15 kW of strip heat usually does not. Only a load calculation answers it, and it takes us a short visit.
Who runs the electrical, my HVAC contractor or an electrician? Some HVAC companies subcontract it, some don’t touch it. Either way, the electrical work in Naperville has to be done by a licensed electrical contractor registered with the city, under a separate electrical permit. Ask your HVAC contractor directly which parts they are and are not doing, in writing.
How far ahead should I call an electrician? As soon as you have model numbers. If a service upgrade turns out to be needed, that involves permit review and utility scheduling, and it does not compress into a few days.
Do I need a disconnect if the panel is right next to the unit? Under the 2023 NEC the outdoor unit needs a disconnecting means within sight and readily accessible. Whether the existing panel satisfies that depends on the specific layout, and it’s a judgment an inspector will make. We’d rather set a disconnect than argue about it at final inspection.
What does a heat pump circuit cost to install? It depends on the conductor run from the panel to the equipment, whether the panel has an open space of the right size, and whether backup heat needs its own feed. We do free estimates with no trip charge and no dispatch fee, so getting a real number costs you nothing.
Talk to a licensed electrician before you commit to equipment
Cob Services LLC is a family owned electrical contractor based in Naperville. We handle heat pump circuits, disconnects, load calculations, panel upgrades, and the permit through the City of Naperville, and we coordinate our schedule around your HVAC contractor’s install date.
Send us the spec sheet and we’ll tell you what your house can take.
Cob Services LLC 2020 Calamos Ct Suite 200, Naperville, IL 60563 Phone: (630) 427-5923 Illinois electrical contractor license #26-00032356 Licensed, bonded and insured. Free estimates, no trip or dispatch fee. Office hours: Monday through Friday, 9:00 AM to 5:00 PM. Emergency line 24/7. Serving Naperville, Lisle, Aurora, Plainfield, Bolingbrook and Downers Grove.
Request service or call (630) 427-5923.