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The Best oil furnace, costs & prices in 2021

Picking the right oil furnace is vitally important. Choosing the wrong one could leave you regretting it for the life of the furnace.. over 20 years!

This is a guide to the best oil furnaces, their running costs, and prices in 2021.

After working in the HVAC industry for over a decade I felt it was time to pass on some of my wisdom.

Picking the wrong oil furnace can be a costly mistake, sometimes costing thousands of dollars over the lifetime of the oil furnace, so I’ve put together this guide to ensure you make the correct decision for your home and your family.

Oil furnaces aren’t exactly new technology however there are some pitfalls that most people still aren’t aware that you need to watch out for.

Oil furnace buying guide in 2021

Buying the right oil furnace is key to keep your home warm and money in your pocket.

An oil furnace should last between 15 and 25 years, depending on the brand and usage. Some lucky people can keep them running for even longer.

This alone shows how important it is to pick the right one.. otherwise, you could be regretting it for over a quarter of a century!

Just quickly.. how does an oil furnace work?

You don’t really need to know how an oil furnace works.. but if you’re interested here’s a very quick overview.

The oil, usually stored in a tank, is burnt at a consistent rate but the oil furnace. When the oil is burnt heat is generated which is caught in an airflow, which is pumped into your home via a blower, or a variable-speed blower.

Pretty simple eh?

Oil furnace pros and cons

Oil Furnace pros
Up to 90% efficiency
Oil is widely available
Oil produces more heat per volume compares to propane and other natural gases
Oil Furnace cons
Compared to propane furnaces, efficiency is lower
Filters must be changed

Oil furnace efficiency

The efficiency of your oil furnace is probably the most important consideration when looking to make a new purchase.

AFUE (Annual fuel utilization efficiency)

The AFUE rating measures an oil furnace’s efficiency in converting fuel (oil) into energy. 

An oil furnace that has an AFUE rating of 85 means that it’s 85% efficient in converting oil into energy, leaving a 15% loss.

The minimal efficiency for a new oil furnace is 83%, which most oil furnaces hitting between 85 and 90%.

This is a vast improvement over oil furnaces of times past, where efficiency could be as low as 70%.. or worse!

In financial terms, an AFUE 85 oil furnace translates to a 15 cents inefficiency loss on each dollar you spend.. although it’s worth noting that no furnace of any fuel type is 100% efficient.

The key takeaway is: the higher the AFUE, the more efficient the furnace is, the more money you’ll save heating your home.

Why the inefficiency?

Oil furnaces typically just have one heat exchanger. This means when the oil is burnt in the combustion chamber, the exhaust gases generally go to waste.

There are a couple of oil furnaces that have two heat exchangers, however, these tend to become a maintenance nightmare so I wouldn’t really recommend them.

The alternatives to consider are a gas furnace or a natural gas furnace which have more energy efficiency but may increase the installation costs.

Oil Furnace running costs

Believe it or not, a more expensive boiler can actually save you money in running costs in as little as 5 – 10 years.

It really is a case of making a good investment now and earning (well, saving) dividends in the future.

Based on the section about AFUE (Annual fuel utilization efficiency) above, we know that oil new furnaces can range from 83% efficient to about 90%. However, your existing old oil furnace may be considerably less efficient.

How much can I save?

I’ve done some calculations to demonstrate the difference AFUE can have on running costs over the life of the boiler.

As a direct comparison, I’ve worked out the approximate saving between a 80,000 BTU 83 AFUE and  80,000 BTU 90 AFU oil furnace.

A 80,000 BTU oil furnace just means it burns 80,000 BTU per hour, which is reasonable to heat our average family home.

If we presume that your home uses the oil furnace for 5 hours a day over 6 months of the year, that totals 910 hours of running time a year.

(If you live in a much warmer climate (or much cooler) the months of usage will clearly differ)

We know that 1 gallon of oil holds approximately 138,500 BTU of energy, therefore:

  • An 83 AFUE oil furnace would extract 114,955 BTU per gallon.
  • A 90 AFUE oil furnace would extract 124,650 BTU per gallon.

This might be getting confusing but bear with me..

Based on the numbers above, each year:

  • A 83 AFUE oil furnace would burn 633 gallons of oil.
  • A 90 AFUE oil furnace would burn 584 gallons of oil.

As you can see, the 90 AFUR saves approximately 49 gallons of oil a year, whilst producing the same amount of heat.

Based on an approximate residential heating oil price of $2.90 per gallon, that’s a saving of $141 a year.

Over the year this can quickly add up:

5 year saving: $705

10 year saving: $1410

15 year saving: $2115

20 year saving: $2820

This doesn’t even take into account very old furnaces with terrible efficiency – this only compares two modern oil furnaces which are available to purchase today!

Fluctuations in the cost of oil

One this to keep in mind with these savings is the price of oil. As you can probably imagine, the price of oil is dictated by events from all amount the world and can vary 20% year on year.

That said, the price of oil does generally seem to rise over the decades. For example, in Jan 1992 a Gallon of oil was under 1 USD. Even taking into account inflation, we can see how the price has gradually risen over time.

This may make your long term savings even greater.

Oil furnace performance

Now that we’ve discussed the efficiency and running costs of heating oil in an oil furnace, it’s time to move on to the performance of the furnace itself.

Before you shout at me “isn’t this the same thing??”, I can assure you there is a difference!

The performance of an oil furnace is referring to the inner workings of the furnace itself. This depends on which models you choose.

Single stage vs 2 stage

Single stage oil furnaces just mean it’s either on or off. There is no 50% power mode.

2 stage oil furnaces, as you might have guessed, allow for a step (or stage) between on or off. This makes things more efficient, as you can burn less oil when the full amount of heat isn’t needed.

That said, the vast majority of oil furnaces on the market are single stage. I’d suggest about 95% of them.

I know that Riello makes at two stage oil furnace system.. but I’m not sure about the other brands.

The Oil furnace blower

The type of blower in the oil furnace also has an impact on performance.

There are variable speed blowers, single speed blower motor and multi-speed blowers.

That’s a lot of blowers!

The types are similar to the single and 2 stage explanation above. The single speed is either on or off, multi speed has different steps, and variable speed can go from 0 t0 full power!

In order of efficiency they go:

Variable speed blower (most efficient)

Multi speed blowers

Single speed blowers (least efficient)

The most efficient, the more money you save on oil.. and save the environment a bit too!

Best oil furnace brands

I would rank oil furnace brands in the following order.

As a warning, the ones towards the top of the list are likely to be the most expensive to buy (and maybe have higher installation costs). That said, the warranty is probably going to be better too. It’s something to speak to your installer about.

  • Carrier and Bryant
  • Kerr
  • Adams
  • Rheem and Ruud
  • Armstrong and Ducane
  • Comfort-Aire
  • Heil, Arcoaire, ComfortMaker (essentially the same brand)
  • Olsen
  • Thermo Pride

Oil furnace size

The size of the furnace is key to ensuring your home gets the right amount of heat at the lowest costs.

If the furnace is too small t your home won’t be warm enough and your furnace will be running overtime to try and keep up! This can’t be good for it and the maintenance costs.

If the furnace is too large it will be overly expensive to install and run, and will likely heat well past the set point.

As you can see, picking the right size oil furnace is particularly important.

How do I know which size I need?

A HVAC contractor is probably the best way of ensuring you pick the perfect size quality furnace.

You can ask them to provide you with a J load calculation.

This calculation, usually done on a computer or laptop, take various data points about your home and provides an accurate calculation for the furnace size.

Some of the information that is put into the calculation is as follows:

  • Home foundation type
  • Outside landscaping
  • Siding Types
  • Roof color
  • Paint / brick color
  • Number of windows
  • Square footage

… and this is just scratching the surface!

That’s why I’d recommend getting in a contractor to do this calculation.. there are just too many variables that you could get wrong.

Oil furnace prices

It’s often hard to find approximate furnace cost and installation.

I’ve put together this table of prices to give you an idea of the furnace cost and installation prices.

These should just be used as a guideline.

  • Kerr $4,500 $8000
  • Adams $4000 $6,500
  • Miller $4000 $6,250
  • Rheem $4,000 $6,250
  • Century $4000 $6,500
  • Olsen $3,500 $5500
  • Thermoflo $3,500 $5,500
  • Comfort-Aire $3000 $5000
  • Armstrong and Ducane $2,500 $3,900
  • Heil $2,500 $4,500
  • Olsen $2,200 $4,100
  • Rheem and Ruud $2,300 $4500
  • Thermo Pride $2,500 $4,500
  • Williamson/Thermoflo $1700 $4,500
  • Crown Boiler $2,200 $4900


What is the best oil furnace to buy?

I feel that the best furnace to buy is a high efficiency (around 90 AFUE) oil furnace, which is the correct size for your home. The right size can be found with the J load calculation.

Which brand of furnace is best?

My favorite brands are Carrier and Bryant, Kerr and Adams.

What is the average cost of a new oil furnace?

The average cost of purchasing the boiler is around $3000, with installation around $5000.


The best oil furnace is one with a high AFUE, which means high efficiency, which will pay for itself over the years.

The brands I’d suggest looking at first are Carrier and Bryant, Kerr and Adams.

It’s important to get the right size oil furnace, which your HVAC contractor can help with via a J load calculation test.

You can get 4 free, no-obligation quotes from local contractors for your new energy efficient furnace here.