Heating oil tank gauge (C) Daniel Friedman Heating Oil Usage Rate
How Long Will a Tank of Oil Last?

InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.

Heating oil usage rate calculations: how to determine the rate of home heating oil consumption:

This article describes how long you can heat your building with a known amount of heating oil in the tank, or how to determine how fast your heating oil consumption is likely to empty the heating oil tank.

If your oil fired heating boiler, warm air furnace, or water heater has stopped working, one of the first things to check is whether or not you've run out of fuel. If your oil tank is above ground indoors or outside it should have a fuel level gauge installed similar to the one shown in our photo.

We also provide a MASTER INDEX to this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need.

How Quickly Is My Heating System Using Up Oil in the Oil Storage Tank?

Heating oil tank gauge (C) Daniel FriedmanHow long will a quarter of a tank of heating oil last?

The thermostat and the temperature in my house is always kept at 68 degF.

If my oil tank gauge reading is 1/4 of a tank, how long will that last???

We have no other heating source, ( I'm comfortable).


Reply: It Depends ..

We cannot answer accurately how long your quarter of a tank of heating oil will keep your home heated from just the information you provided, but we can list the facts you'd need to know and how you could estimate or find out the answer:

What Determines How Long a Tank of Oil Will Last?

How long a tank or part of a tank of heating oil will last at a building depends on the following variables:

How to Make a Rough Guess at How Long the Oil Tank Will Last

You can make a very rough guess by noting how many minutes per hour or day your oil burner is running. Oil burners use a spray nozzle that delivers oil at some flow rate in gallons per hour, typically on a home, around .8 to 1.7 gallons per hour.

On your boiler or furnace will be a data tag that gives the maximum recommended flow rate in gallons per hour. With the gallons per hour (GPH) and minutes of run time you are observing you can multiply GPH x (minutes of on time per day / 60 minutes per hour) = number of gallons of oil being consumed a day.

Of course this varies widely as weather and temperatures and house leaks vary, as we outlined just above.

So if you know your oil tank size (say 500 gallons) you can make a very rough guess at how much oil is in the oil tank - say 125 gallons. I'd round down to 100 to be on the safe side since the tank is probably round or oval.

Example of Calculation of Days Supply of Heating Oil Remaining in an Oil Storage Tank

G = Gallons of oil remaining the tank

GPH = oil consumption rate when the oil burner is running, in gallons per hour - the largest number on your oil heater's data plate, or the actual GPH number for the oil burner nozzle actually installed on your oil burner (usually this is smaller than the data tag maximum)

MPH = minutes per hour that your oil burner is running, averaged over 24 hours per day, from observation

GPD = (GPH x MPH / 60) = gallons of heating oil used per day

Here is an example using some sample numbers: 100 gallons of oil in the oil tank and a 1 GPM oil burner nozzle.

G=100 gallons of heating oil in the tank

GPH = oil burner nozzle deliver rate in gallons per hour (from data tag on oil heater or number stamped on oil burner nozzle)

MPH = 15 minutes per hour that the oil burner is actually firing (from observation)

15 (minutes of "burner on time" per hour) x 24 (hours in a day) = 360 minutes of burner on time per day

GPD = 1 (GPH) x (360 (burner on time per day) / 60 (minutes per hour)) = 6 gallons of oil used per day.

100 G (gallons of oil in the tank) / 6 (gallons of oil used per day) = 16.6 days of heating oil supply remaining

Thanks to reader Cass for careful technical editing 3/23/2014 - Ed.

Watch out: calculating the number of days of heat that oil in your tank can provide is very rough, since outdoor temperatures, wind, and other conditions keep changing. Your oil company knows this and uses a more sophisticated approach using degree days - a factor that considers not only your oil burner's usage rate but how that rate will vary as a function of changes in outdoor temperature.

Bottom line: if your oil tank shows 1/4 full or less and it's during the heating season, you ought to call your oil company and ask for a delivery soon.

In an emergency if you are out or almost out of heating oil and your oil company can't make a delivery soon enough, the oil company can send a technician who can bring a 5-gallon container of oil to pour into your heating oil tank, or you can yourself purchase diesel fuel (in an emergency only) at a gas station and use that.

If you run out of heating oil, re-starting the oil burner may require a service call from your heating company as it may be necessary to bleed air out of the oil piping in order to properly re-start the oil burner.

Extreme danger: Double watch out: if you are purchasing fuel to use in your heating oil tank, be sure it's heating oil or in an emergency, diesel fuel or kerosene. If you put other flammables into your heating oil tank you are likely to blow up the building and kill everyone.

Your Oil Company Knows How Long Your Oil Tank Will Last

If you are on automatic oil delivery the question of how long the oil tank will last is easier to answer - your oil company will have computerized data showing your home's oil consumption rate as a function of "degree days" - a rough measure of how many hours at what outdoor temperature your home is being exposed to winter weather. They can tell you your home's energy consumption rate more accurately.

How Much Oil is in the Oil Tank (if no gauge is installed)?

Probing a buried oil tank (C) Daniel FriedmanYour oil company can provide a stick, a folding rule, or even a string and weight that can be placed into an oil tank to locate the bottom of the tank and to determine the level of oil in the tank.

The depth of the oil in the tank is measured by marking the top of the tank on the stick or oil tank gauge, then placing the stick into the oil tank and withdrawing it. The oil level seen on the stick is compared with the distance from bottom of the stick (bottom of the oil tank) to top of the oil tank (which we marked on the stick).

In the old days people kept an oil tank stick that was already marked and calibrated to tell them how much oil was in their tank.

Today if we use a folding measuring rule or a generic "stick" to "stick the oil tank" to check oil level, we need to know the volume and shape of the tank as well as the depth of oil on the stick in order to calculate the number of gallons in the oil tank accurately.

In the photo our client is discovering a surprise buried oil tank at a farm we were inspecting.

Vapourising oil heating equipment

Wyn Parkin said:

I note that there is no mention on the site about vapourising oil boilers such as the Harmony range from Efel or Nestor Martin

Reply: free-standing space heaters that use a vapourising oil burner

Thanks Wyk, I'm working on that interesting addition.

It's worth noting that the heaters you cite are typically free-standing auxiliary heating sources. They are not central heating boilers nor central heating furnaces. They're more like an alternative to a wood or coal stove. However there are indeed (by other brands and applications) vaporizing oil burners and boilers used including in some commercial applications. Here we will address the type of heaters you cited:

Euroheat (a UK energy company) provides information about the Harmony Range and Efel, describing them as wood-burning / multi fuel stoves.

Eireheat [dot] com provides a nice description of vaporizing heaters from Nestor Martin (Belgium) heaters. We excerpt:

Nestor Martin stoves are equipped with a high-effi ciency stainless steel vaporizing burner to ensure clean, thorough combustion. The burner is fed a monitored fl ow of oil into the bottom of its cylindrical body, where the oil is heated and becomes vaporized.

As the vapor rises, it draws into the burner the air necessary for combustion through critically positioned and sized inlets.

The flame is stabilized and the combustion process maintained at the correct temperature by the catalyser.

The heat output of the burner is controlled by a carburetor which is manually controlled, giving you total command of the flame height at all times.

If you have other citations I'd appreciate receiving them (you can use our email found at our CONTACT link)

and we'll be glad to expand on the topic.

(Oct 17, 2014) Wyn Parkin said: Harmony range & Efel (Nestor Martin) heaters

Thanks for your answers, however, a few of the harmony range are fitted with 2-part boilers that form an L shape inside the unit. One supplies the domestic hot water and the other goes to the home heating.

I note that some of the oil fired boilers mentioned, eat up the fuel in Gallons Per Hour, whereas the Harmony 2 with its 10 inch burner (also supplied in 8 inch size)(and 6 inch for other models) on its lowest setting uses approximately 5 cc of fuel per minute (300cc per hour) of kerosene fuel.

The boiler is virtually silent in operation as it has no moving parts, and we have found that it is more than adequate for our 3 bedroom detached house, used mainly on setting no 2 out of 6.

Unfortunately, I have recently found (while searching for a spare part) that Efel (Nestor Martin) have gone into liquidation following a massive fire at their foundry in one of the Scandinavian countries.

Most parts are still available but the part I needed was a new coals bed (artificial coals that glow) was not available for my model, but I succeeded in replacing it with a coals bed from a Harworth Heating, Bubble 2 boiler. Looks almost the same!


Continue reading at HEATING COST SAVINGS METHODS or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.


Suggested citation for this web page

HEATING OIL USAGE RATE at - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.


Or use the SEARCH BOX found below to Ask a Question or Search InspectApedia


Frequently Asked Questions (FAQs)

Click to Show or Hide FAQs

Ask a Question or Search InspectApedia

Try the search box just below, or if you prefer, post a question or comment in the Comments box below and we will respond promptly.

Search the InspectApedia website

HTML Comment Box is loading comments...

Technical Reviewers & References

Click to Show or Hide Citations & References

Publisher's Google+ Page by Daniel Friedman