Guide
Electrical requirements for a heat pump: circuits, disconnects and old Bellingham panels
Every heat pump needs a dedicated circuit and a service disconnect, and pre-1960 Bellingham houses on 100-amp service sometimes need more. All electrical work is done by a licensed electrical contractor — we do not hold that licence.
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- We pull the permit City of Bellingham or Whatcom County, and we meet the inspector
The electrical scope is where heat pump projects surprise people, and it is also the part we do not perform. All electrical work on our projects is performed and permitted by a licensed electrical contractor, and Bellingham Heating and Cooling does not hold an electrical contractor licence. What we do is coordinate that scope, sequence it with the mechanical work, and make sure you know what it involves before you sign anything. A heat pump needs a dedicated circuit sized to the equipment, a service disconnect within sight of it, and correct conductor and overcurrent protection. Pre-1960 Bellingham stock on 100-amp service sometimes needs a service upgrade to carry that, and removing electric baseboard can free up the capacity instead.
What we do and do not do, stated plainly
Bellingham Heating and Cooling LLC is registered with Washington L&I as a general contractor under registration BELLIHC808NM. There is no electrical contractor licence under our UBI, and no plumbing contractor licence either.
So the correct description of our role on the electrical side is coordination, not performance. A licensed electrical contractor sizes and installs the circuit, the disconnect and any panel work, and pulls the electrical permit for that scope. We install and commission the mechanical equipment, pull the mechanical permit, and meet the mechanical inspector.
We are telling you this because it changes how you read a quote. If a contractor’s heat pump quote silently includes electrical work, ask who holds the licence and who pulls the electrical permit. It is a fair question and the answer should be immediate.
What a heat pump needs electrically
A ducted heat pump typically needs a dedicated 240-volt circuit for the outdoor unit, sized to the equipment’s minimum circuit ampacity and protected at or below its maximum overcurrent protection rating. Both numbers are printed on the unit’s data plate and are equipment-specific rather than generic.
It needs a service disconnect at the outdoor unit, so a technician can positively de-energise the equipment while standing next to it. If the system includes electric resistance backup heat in an air handler, that is usually its own circuit and often the largest single load in the project.
A ductless system needs a dedicated circuit as well, and depending on the manufacturer the indoor heads may be powered from the outdoor unit or independently. Multi-zone systems need control wiring between the outdoor unit and each head, run alongside the refrigerant lineset.
| Project | Circuits involved | Where the surprises come from |
|---|---|---|
| Single-zone ductless | One dedicated 240-volt circuit plus a disconnect at the outdoor unit | Distance from panel to unit, and whether a route exists that does not mean opening finished walls |
| Multi-zone ductless | One dedicated circuit for the outdoor unit plus interconnecting control wiring to each head | Control wiring routes to heads on the far side of the house |
| Ducted heat pump with electric backup | Outdoor unit circuit, air handler circuit, and backup heat strip circuits | Backup heat is often the largest load and the reason a panel runs out of room |
| Furnace to heat pump conversion | New outdoor and air handler circuits; the old furnace circuit is rarely adequate | People assume the existing furnace circuit is reusable, and it usually is not |
| Heat pump water heater | A dedicated circuit, plus condensate handling that is not an electrical question but arrives at the same time | A location that satisfies the 40°F to 90°F requirement may be far from the panel |
Pre-1960 Bellingham stock and 100-amp service
A substantial share of Bellingham’s older housing — the 1890s to 1930s cottages and four-squares — is still on 100-amp service, and some is on less. That was ample for a house heated by a stove or a furnace and lit by a few circuits, and it is tight for a modern all-electric house.
The question a licensed electrician answers is not "is 100 amps enough" in the abstract but a load calculation for your specific house and your specific new equipment. Sometimes 100 amps is genuinely fine. Sometimes the panel has no physical space left even though the service is adequate, which is a cheaper problem to fix.
What pushes a project over the line is usually electric resistance backup heat, an electric range, an electric water heater and an EV charger arriving in the same decade. If more than one of those is in your plans, having the load calculation done once, covering all of them, is much better than discovering the limit twice.
How removing baseboard can pay for the upgrade
Here is the piece of good news that gets missed. If you are converting from electric baseboard or wall heaters, you are removing load at the same time you are adding it, and baseboard circuits in an older Bellingham house can add up to a lot of amperage.
That means a conversion project sometimes needs no service upgrade at all, even in a house that would fail a load calculation with the baseboards left in place. The panel may need reconfiguring and the abandoned circuits properly dealt with, but that is a fraction of a service upgrade.
It also means the sequence matters. Tell the electrician what is being removed, not just what is being added, and make sure the load calculation reflects the finished condition of the house rather than a snapshot mid-project.
When a panel or service upgrade is genuinely needed
Sometimes the answer is a service upgrade, and it is better to know that at quoting time than at install time. The signs to look for are a 100-amp or smaller service with no spare capacity, or a panel with no available spaces and no legal way to add them. An obsolete or recalled panel type, or aluminium branch wiring an electrician wants to address anyway, points the same way.
A service upgrade involves the utility as well as the electrician, because PSE owns the service drop and the meter, and that adds coordination and schedule. It is not a same-week item.
On cost, there is one genuinely useful incentive: Washington’s HEAR program explicitly includes electrical panel and wiring upgrades as an eligible category, administered locally through Sustainable Connections, the Opportunity Council and Lummi Nation for income-qualified households. Per-household amounts are set by the administrator and are not published, so the honest advice is to ask them directly rather than to assume a figure.
Permits, inspections and sequencing
Electrical work is permitted separately from mechanical work. The licensed electrical contractor pulls the electrical permit and their scope gets its own inspection; we pull the mechanical permit and meet the mechanical inspector.
Sequencing matters because the equipment cannot be commissioned until it has power, and the electrical inspection may need to happen before concealment. On a project with any wall opening, get the order agreed in advance: rough-in, inspections, close up, then mechanical commissioning.
We will name the electrical scope on the quote as a separate line, and we will tell you whether it is included in our price as a coordinated subcontract or whether you are contracting the electrician directly. Both are workable. What is not workable is leaving it unstated until install day.
Questions Bellingham homeowners actually ask
- Do you do the electrical work?
- No. All electrical work on our projects is performed and permitted by a licensed electrical contractor, and we do not hold an electrical contractor licence. We coordinate that scope, sequence it with the mechanical work, and make sure it is on your quote as a named line rather than a surprise.
- Will my 100-amp panel run a heat pump?
- Often yes, and a licensed electrician answers it with a load calculation for your specific house and equipment rather than a rule of thumb. Converting from electric baseboard helps considerably, because you are removing load as well as adding it. Electric resistance backup heat is usually what tips a marginal service over the line.
- What is the disconnect for?
- It lets a technician positively de-energise the outdoor unit while standing next to it, rather than trusting that the right breaker was switched off inside the house. It is a required part of the installation and it is genuinely the difference between safe service work and hoping.
- Can I reuse the circuit from my old electric furnace?
- Sometimes for the air handler, rarely for the outdoor unit, and never on assumption. Conductor size, breaker rating and the equipment’s minimum circuit ampacity all have to line up with the new data plate, and that is the electrician’s determination based on the specific equipment.
- Is there help paying for a panel upgrade?
- For income-qualified households, yes: Washington’s HEAR program lists electrical panel and wiring upgrades as an eligible category, administered locally by Sustainable Connections, the Opportunity Council and Lummi Nation for households at or below 150% of area median income. Per-household amounts are set by the administrator and are not published, so contact them for your number.
- Does a mini split need less electrical work than a ducted system?
- Usually yes, and that is one of its quiet advantages. A single-zone ductless system typically needs one dedicated circuit and a disconnect, with no electric resistance heat strips to feed. A ducted system with backup heat can need several times the capacity.
Have us apply this to your house
Reading it is one thing. Send us the address, the panel size and what you heat with now, and we will tell you what it means for your project.
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