# Replacing Oil Heat with a Mini Split in Portland, OR

> Replacing oil heat with a mini split in Portland: ductless heads sized for winter, the oil furnace removed, and the tank emptied under DEQ rules.

URL: https://firlandsportlandminisplits.com/oil-heat-to-mini-split/

Service

Replacing oil heat with a mini split: ductless heads sized for winter, the furnace out, and the buried tank handled under DEQ's rules.

(971) 458-4515

Last Updated: November 12, 2026

Room by room

Each head sized to its room, not to the square footage

Tested

Nitrogen pressure test and a deep vacuum on every line set

Drained

A planned drain or pump for every head, tested with water

Permitted

Mechanical and electrical permits on every install

The oil furnace in the basement is loud and old, every tank fill costs more than you’d like, and the house has never had cooling. You want off oil, and you’re not sure what to do about the tank in the yard.

Replacing oil heat with a mini split puts ductless heads in the rooms the furnace heated, takes the furnace out, and gets the tank emptied as Oregon law requires. [Firlands Portland Mini Splits](https://firlandsportlandminisplits.com/) plans the heat, removes the furnace, and schedules the tank work so nothing is left half done.

## Is a mini split the right replacement for your oil furnace?

It’s a strong fit when the old ducts are small, leaky or cramped, and you want cooling and room-by-room control.

| A mini split fits well | Look at a ducted heat pump instead |
| --- | --- |
| Ducts are small, leaky or run through a tight basement | Ducts are sound, sized well and reach every room |
| Rooms are used differently and want their own setting | You want one thermostat for the whole house |
| The house is one-and-a-half stories with rooms under the roof | A full basement and attic make new ducts easy |

A ducted central heat pump that reuses the old ducts is a different job, and not one we do. [Mini split vs central heat pump](https://firlandsportlandminisplits.com/guide/mini-split-vs-central-heat-pump/) sets the two side by side.

Project

## Inside a St. Johns oil-to-ductless conversion

### The problem

The oil furnace in the basement is old and loud, each tank fill costs more than the last, and the house has no cooling. The owner wants off oil completely.

### The house

Living and dining run together on the main floor next to one bedroom; two rooms under the roof share the upstairs. The oil tank is buried in the side yard, and the house's old ducts are small, leaky and run through a cramped basement.

### What we decide, and why

Three heads replace the furnace entirely: 15,000 BTU in the living and dining room, 12,000 for the upstairs rooms, which stay open to each other, and 9,000 in the main-floor bedroom. All are cold-climate models sized for Portland's 24°F design low. The bathroom keeps the small electric wall heater it already has. The owner chooses ductless over reusing the old ducts; a ducted central heat pump is a different job.

### The work

The heads go in first and run for a day before the furnace comes out, so the house is never without heat. We disconnect and remove the furnace, its oil line and flue pipe, and seal the chimney opening. A new 240-volt circuit runs to the outdoor unit on a pad at the back of the house. Then the tank: we schedule a DEQ-licensed heating oil tank provider to pump it out and decommission it in place.

Oregon law requires a heating oil tank to be emptied when the house stops using it, and it's illegal to disconnect one without pumping it out. Lining the tank work up with the furnace removal means the oil line is never cut while oil is still in the ground.

### What it changes

No oil deliveries, heat and cooling in every main room, and the tank provider's certification paperwork for the owner to keep for a future sale.

Location

St. Johns, North Portland

House

1930s one-and-a-half-story, about 1,400 square feet, oil furnace and a buried oil tank

Equipment

Three heads (15,000, 12,000 and 9,000 BTU) on one 36,000 BTU cold-climate outdoor unit

Price

$16,200, permits and furnace removal included; tank work priced by the tank provider

Time on site

3 days after permits, plus one day for the tank work

## What happens on the first visit

We look at the house the way the furnace heated it, room by room, and then at the tank.

We measure each room, note the windows, insulation and ceiling heights, and work out each room’s load. Where a house has rooms under the roof, they swing hardest between winter and summer, and they get their own heat. Then we check:

- **The panel.** An oil house often has spare breaker space, and sometimes a small electrical service that needs a look.
- **The outdoor spot.** Side or rear yard, under five feet tall, out of the front setback.
- **The furnace and flue.** How they come out, and how the chimney opening gets sealed.
- **The tank.** Buried or in the basement, where its fill and vent pipes are, and how it’s reached.

You get a written estimate listing every head and its capacity, the outdoor unit, the line-set routes, the drains, the circuit, the furnace removal, the permits, the price and what’s not included. The tank work is priced by the licensed tank provider.

## The tank: what Oregon requires

When a house stops using a heating oil tank, the tank has to be emptied. It’s illegal to disconnect one without pumping it out first.

That’s ORS 466.878, and Oregon DEQ sets out how the work is done. Homeowners can do it themselves, but anyone you hire has to be a DEQ-licensed heating oil tank services provider, who certifies the work to DEQ.

### Pump-out and decommissioning

- **Pump-out** removes the remaining oil and is the minimum the law requires.
- **Decommissioning** goes further: the emptied tank is cleaned and filled in place, or dug up and removed.
- **Certification** from the licensed provider is the record DEQ keeps and a buyer will ask for.

### Where oil heat is still common

About 1.8% of Portland homes still heat with oil, by the Census Bureau’s count. [North Portland](https://firlandsportlandminisplits.com/service-areas/north-portland/) has the highest share of any district, at 2.7%, and [Southeast](https://firlandsportlandminisplits.com/service-areas/southeast-portland/) has the most oil-heated homes by number.

### How we fit it into the job

We schedule the licensed provider and line their visit up with the furnace removal. The oil line is never cut while oil is still in the tank, and the house is never without heat.

## Heating the house without the furnace

When heads replace the only heat source, we size them for the coldest nights, not a mild day.

Portland’s design low is 24°F, and the January 2024 ice storm took the airport to 15°F. We choose cold-climate outdoor units by their published heating output in the cold.

- **Every closed room is covered.** It gets its own head or shares an open space with one.
- **Rooms under the roof get attention.** They lose heat fastest in January and gain it fastest in July.
- **A backup stays.** A small electric heater kept in the bathroom covers the rare winter repair.

[Do mini splits work in cold weather?](https://firlandsportlandminisplits.com/guide/do-mini-splits-work-in-cold-weather/) explains the ratings, and [how many mini splits do I need?](https://firlandsportlandminisplits.com/guide/how-many-mini-splits-do-i-need/) helps with the count.

## The order of the work

The sequence keeps the house heated the whole way through.

1. **Permits.** Mechanical for the heat pump and electrical for the new circuit.
2. **Heads and outdoor unit.** Holes, line sets, drains, the circuit, the pressure test and vacuum.
3. **Run the new system.** At least a day on the heads before the furnace goes.
4. **Furnace out.** The furnace, oil line and flue pipe removed, the chimney opening sealed.
5. **The tank.** Pumped out and decommissioned by the licensed provider.
6. **Finals.** The city’s final inspections and the provider’s certification handed over.

## What it costs

Firlands’ typical range for three or four heads is **$9,000 to $18,000 and up**; whole-house systems with five or more heads typically run **$15,000 to $30,000 and up**.

| Job | Typical range |
| --- | --- |
| Three or four heads on one outdoor unit | $9,000 to $18,000+ |
| Whole house, five or more heads | $15,000 to $30,000+ |
| A service upgrade if the panel can’t take it | $2,500 to $6,000 |

Furnace removal is on our estimate; the tank pump-out and decommissioning are priced by the licensed provider. Your price comes from the visit and the written estimate, with the city’s permit fees included.

Energy Trust’s ductless incentive is for homes replacing electric resistance heat, so an oil-heated house falls outside that offer; [mini split rebates in Oregon](https://firlandsportlandminisplits.com/guide/mini-split-rebates-oregon/) lists what else is open. [Mini split electric bill](https://firlandsportlandminisplits.com/guide/mini-split-electric-bill/) covers running costs.

## Related jobs

If your house needs more, or less, than a straight oil swap, one of these may fit better.

- **Every room, five or more heads:** see [whole-house mini splits](https://firlandsportlandminisplits.com/whole-house-mini-split/).
- **Only the main rooms for now:** a [multi-zone system](https://firlandsportlandminisplits.com/multi-zone-mini-split-installation/) can start there.
- **An old house with no ducts upstairs:** [adding air conditioning to an old Portland house](https://firlandsportlandminisplits.com/guide/adding-air-conditioning-to-an-old-portland-house/) covers the choices.

## What's included

- A room-by-room heat plan, with a backup-heat decision written down
- Ductless heads sized to each room, and matched cold-climate outdoor units
- Line sets, drains and pumps for every head
- Dedicated 240-volt circuits and disconnects
- Removal of the oil furnace, its oil line and flue connector, with the chimney opening sealed
- Scheduling the tank pump-out and decommissioning with a DEQ-licensed provider
- Pressure tests, deep vacuum, startup and a walk-through of every head
- Permits and the final inspections

## Leaving oil: what are the choices?

|  | Ductless mini split | Ducted central heat pump | Keep the oil furnace |
| --- | --- | --- | --- |
| Uses the old ducts | No | Yes, if they're sound and big enough | Yes |
| Cooling | Every room with a head | Whole house | None |
| The tank | Emptied, usually decommissioned | Emptied, usually decommissioned | Stays in service |
| Typical range | $9,000 to $18,000+ (three or four heads); $15,000 to $30,000+ (whole house) | A different job, not ours | Fuel and repairs |

## Related resources

- [Learn**Do mini splits work in cold weather?** Portland's winters are mild with sharp exceptions: freezing rain, an east wind and a few nights in the teens.](https://firlandsportlandminisplits.com/guide/do-mini-splits-work-in-cold-weather/)
- [Decision Guide**Mini split vs central heat pump: which fits a Portland house?** It comes down to your ducts: whether they exist, where they reach, and what shape they're in.](https://firlandsportlandminisplits.com/guide/mini-split-vs-central-heat-pump/)
- [Learn**How many mini splits do I need?** Count the rooms you close a door on, not the square feet. Then group the heads onto outdoor units.](https://firlandsportlandminisplits.com/guide/how-many-mini-splits-do-i-need/)
- [Learn**What mini split rebates are available in Oregon?** What Energy Trust pays, which homes qualify, how state and city programs work, and what's changed for the federal credit.](https://firlandsportlandminisplits.com/guide/mini-split-rebates-oregon/)
- [Learn**How much will a mini split add to my electric bill?** Running costs worked out from PGE, Pacific Power and NW Natural rates, against baseboards and a gas furnace.](https://firlandsportlandminisplits.com/guide/mini-split-electric-bill/)
- [Learn**How do you add air conditioning to an old house in Portland?** Adding air conditioning to an old house in Portland: bungalows and foursquares with no ducts upstairs, after the heat dome.](https://firlandsportlandminisplits.com/guide/adding-air-conditioning-to-an-old-portland-house/)

## How a job runs

### The call

You tell us the rooms and send a few photos; we give a rough range.

### The visit

We measure each room, look at the walls, the panel and where the outdoor unit can go.

### The estimate

A written estimate: each head, the line-set route, drains, circuit, permits and price.

### Install and handover

Pressure test, vacuum, startup, a walk-through, and the permits closed out.

## Oil heat to mini split: questions

### What happens to the oil tank when I switch to a mini split?

Oregon law requires the tank to be emptied once the house stops using it, and it's illegal to disconnect a heating oil tank without pumping it out. You can also have it decommissioned, filled in place or removed. If you hire anyone for that, DEQ requires a licensed heating oil tank provider, who certifies the work to DEQ.

### Can mini splits replace an oil furnace completely?

Yes, if every room the furnace heated gets heat from a head or shares an open space with one, and the outdoor units are cold-climate models sized for Portland's 24°F design low. A small electric heater kept in the bathroom is a simple backup.

### Is a mini split cheaper to run than oil heat?

It depends on what oil costs when you fill the tank and on your electric rate, both of which move. A heat pump delivers several units of heat for each unit of electricity, and an old oil furnace loses heat up the flue and through leaky ducts. Your bill also loses the tank fills and the furnace service.

### Does Energy Trust pay toward replacing oil heat with a mini split?

Energy Trust of Oregon's ductless heat pump incentive requires the heads to replace electric resistance heat in the main living space, so a house moving off oil doesn't fit that offer. Check our rebates guide for other programs and their current funding.

### Do I need the tank paperwork when I sell the house?

Yes. Under ORS 466.878 the seller gives the buyer documentation that the tank was emptied. A decommissioning by a licensed provider comes with the certification it files with DEQ, which is the paper a buyer's inspector will ask for.

## Related services

- [Service**Whole-house systems** Whole house mini split installation: every room heated and cooled by ductless heads, planned as one system with a winter backup plan.](https://firlandsportlandminisplits.com/whole-house-mini-split/)
- [Service**Multi-zone installation** Multi zone mini split installation: two to five rooms on one outdoor unit, each head sized to its own room and set to its own temperature.](https://firlandsportlandminisplits.com/multi-zone-mini-split-installation/)
- [Service**Baseboard to mini split** Replace baseboard heat with a mini split: ductless heads take over in the rooms that use the most heat, and add cooling.](https://firlandsportlandminisplits.com/baseboard-heat-to-mini-split/)

## Get an estimate for oil heat to mini split

Which rooms, when they're uncomfortable, and what heats them now. We'll call back with a rough range and set up the visit.

(971) 458-4515