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Heating oil tank gauge (C) Daniel Friedman Heating Oil Usage Rate

How Long Will a Tank of Oil Last?

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.

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

Probing a buried oil tank (C) Daniel FriedmanThese questions & answers about the rate at which your heating equipment will use up a tank of heating oil were posted originally at x - be sure to read that article too.

Question: how many liters of kerosene is my house using per hour?

I would like to know how much liters is my house heating using per hour. I bought 181 liters of Kerosene for my heating, how long will it last? Our thermostat has a scale that goes from 7 to 1 and right now is at 1.

I've been using 4 hours of heating per day. My heating has a power of 17.6 kW and efficiency of 65%. Any clues on how much liters it is consuming per hour and how long my 181 liters will last? Thank you - L.F.S. 3/15/2013

Reply:

Your oil burner sprays oil through a nozzle whose job is to aerosolize the oil so that it can be ignited and burned in the combustion chamber. Every oil burner nozzle has a number stampled into its body that gives a flow rate in gallons per hour or GPH (convertible to liters per hour or LPH if you like).

For example a nozzle marked 1.25 is rated to burn 1.25 gallons of No. 2 home heating oil per hour, presuming that the oil burner's pump is also pushing oil through the nozzle at a specified pressure (typically 100 psi).

If your oil burner is set to a higher pressure (say 140 psi) then more oil per hour is going to pass through that nozzle.

So you could ask your heating service tech to tell you what sized oil burner nozzle is on your heater and what pressure the system runs-at.

But this data is only conceptual - it will NOT tell you how many days of heat you have in your 181 liters of kerosene.

Translating your question in to how long your tank of kerosene is going to last is a bit more tricky than just knowing the kerosene or heating ol burn rate.

The number of hours per day that your oil burner will be "on" depends on

How could we know the heat loss rate of your home from just your email? If someone leaves a window open or turns the temperature up or the outside temperature drops, all of the data changes.

You could look at the oil burner or kerosene burner consumption rate - the nozzle gives a gallons-per-hour flow rate for an assumed flow pressure - and calculate the theoretical numbrer of "on-hours" your burner can run before you've burned up all the fuel, but that will NOT tell  you how many days of heat you have.

Your heating oil company keeps track of "degree days" - that factors in the outdoor temperatures in your area along with the heating fuel consumption rate they have observed for your home in the past - that's how they know when to make an automatic delivery.

So the best answer is to give your heating company a call and ask them what their computer says is your consumption rate based on a theoretical "average degree day" temperature range, then you'd have to watch the actual outdoor temperatures or local degree day data (which you can obtain locally) to know what to expect.

What I do is take a look at the heating oil storage tank gauage every week or so, more often in very cold weather and always if I read that a big cold snap or storm are coming; if the gauge is at 1/4 or below I call and ask for an extra delivery.

Reader Comment:

3/23/2014 cass said:

Hello,
Great site!
Just wanted to let you know, the math on the home heating oil is slightly inconsistent.
inspectapedia.com/oiltanks/Heating_Oil_Consumption_Rate.php

"Here is an example using some sample numbers:
MPH = 15 minutes per hour that the oil burner is actually firing (from observation)"

Here you jump from 15m/hour to 30min/hour...

30 (minutes of "burner on time" per hour) x 24 (hours in a day) = 720 minutes of burner on time per day

GPD = 1 (GPH) x (720 (burner on time per day) / 60 (minutes per hour)) = 12 gallons of oil used per day.

Now you put 6 gal / day, but calculate on 12 gal per day...

100 G (gallons of oil in the tank) / 6 (gallons of oil used per day) = 8 days of heating oil supply remaining"

I was confused by this for a bit, until I realized this.

Thanks again for putting this out there!
-Cass

Reply:

Thanks Cass, I have corrected the math. We appreciate your careful reading and your taking the time to comment - working together makes us smarter.

Daniel

Question: wonders about heating oil usage rate

(Jan 2, 2013) Karen said:

Something seems very off in these calculations. I live in New England and at my old 1,500-square-foot house, I would usually use 500-600 gallons of heating oil PER WINTER (and this is with the thermostat set at 68-72 during the day and 62 at night).

My current house has 2,400 square feet and typically goes through about 800 gallons PER WINTER.

Your calculations above show that 100 gallons of oil = 8 days of heating, which would mean the homeowner would go through 400 gallons in just over a month!

Unless the house is a mansion with no insulation at all AND outside temps are way below normal, that is just insane.

Reply:

Karen: you can sanity check heating oil usage rates if you know the GPH rating of your oil burner nozzle. If your burner uses a 1 GPH nozzle and IF the burner is staying on 50% of the time (for example in very cold weather or in a house with a high heat loss rate), your system will be using 12 gallons of oil per day.

To have a meaningful understanding of your high heating costs and oil usage rate, you will need to consider other things that affect how much heating oil is used, of which here are just a few examples:

(Jan 5, 2013) Anonymous said:

Well Karen don't ever move because I live in new england too and unless your house is super insulated.....which mine clearly is not! I rent. This is very actuate!

(Mar 1, 2013) Anonymous said:

Wow so you're going through 400 gallons of heating oil a month? At the price of heating oil now that means you're paying $1400 a month in heat. I rent too, the bottom floor of a not-well insulated house. I've been going through about 100 of heating oil a month, by keeping my heat at 55 degrees when I'm at home (day and night) and 50 when I'm not. It sucks.

I'm paying $350 a month to barely heat the place which is almost as much as my rent. I've only lived in places with electric heat before, and never paid more than $100 a month, and that was keeping the heat at 75. I am so moving out of this place once my lease is up.

Question: can I change the oil burner nozzle to a different spray pattern

(Jan 6, 2013) nathan S said:

Can I use 1.0 80A nuzzel instead of 1.0 70A? How is it effect my oil heater?

Reply:

While small oil burner nozzle range adjustments usually don't cause trouble among oil burner nozzle sizes,

Watch out: Don't change the nozzle spray pattern to one that is not recommended by the burner/boiler manufacturer. A too wide spray for the combustion chamber, if it impinges on chamber sides, may not burn oil properly.

Question: can we use all of the oil in an oil storage tank or not?

(Mar 10, 2013) Chloe said:

Hi,
we still have about 3- 4 inches deep left in out tank which is about 6-7 ft long and 2 ft wide. The engineer is telling us we dont have enough heating oil left thats why our heating is not working but this seems reidiculous to me. Does this sound normal or am i right in thinking this is hooey.
Thanks

Reply:

Chloe,

Your engineer is probably right - especially if oil lines come off of the top of the oil tank; the installer doesn't want to pick up oil from the very bottom - in an attempt to avoid picking up water and crud that will clog the oil burner.

Mar 16, 2013) Anonymous said:

once the oil level goes below the intake valve your kaput! less than 4 inches in the tank no heat!

Question: ran out of oil, pick up tube experiments

(Mar 20, 2013) Middletown H&C said:

My Armstrong 80 quit.Tech said it was out of oil.I found the pickup tube 24" above bottom I added an extension and then had 100 gals. delivered on 02/27/13.

The second tech said it was the oil filter,which was very old,I had the updated # and he had one,installed it,good oil and heat.When the room met thermostat temp ,it did not come on again.

He replaced the pump,and I have heat.Problem: bad oil smell ,used 100 gal in less than a month in a very small 1 bed room apt. .

My research pointed to a wrong size nozzle.They changed the nozzle.They will not replace my oil.

Any ideas how I can approach this,I'm a renter,DAV, on limited income..

Reply:

Middle:

Sounds like a combination of inadequate oil burner maintenance that finally caught up with you. The oil filter needs to be changed at least annually, along with nozzle at the oil burner along with system cleaning and tuning.

Extending the oil pickup down in your oil tank got at more oil but also may have sent extra sludge and crud through the system, speeding up the clogging problem.

Search InspectApedia for

Heating Oil Tank & Piping Sludge Problems & Cures

to read details about improving your system's operation and reliability.

In the More Reading links at the end of this article see

HEATING COST SAVINGS METHODS

that may also give you a hand.

Question: ran out of oil, how long will 5 gallons of kerosene last?

(Feb 13, 2014) Rob said:

I ran out of oil yesterday about 3:30 pm and bought 5 gallons of kerosene and so far I still have heat I am just wondering is it going to last through the I won't get a delivery until tomorrow around 3:00 my house is about 1400 sq. ft. and I keep my temp. at 68 degrees

Reply:

Rob, I would go out for another 5 gallons now before you run out. A typical home heating oil burner consumes fuel at a rate set by the burner nozzle size rated in GPH and adjusted by oil pressure as well. Higher pressure settings make a 1 GPH noaale consume fuel at a faster rate.

If you knew the nozzle size you'd know it's nominal fuel use rate per hour of on time. If you knew if pressure was set above 100 psi we could look up the true GPH usage rate. If then you had an idea how many hours your burner is ON in each 24 hour period you could computhe the gallons of fuel youll use. Of course you can conserve fuel by lowering the thermostat setting too.

Without those details I can only advise buy more fuel and set back the thermostats.

Question: increase in oil consumption rate

(Mar 15, 2014) patrice michaud, stranorlar said:

the consumption of heating oil in my home became very big this last 3 months,i use 300 liters every 5 weeks,i get a burner service but nothing change!

there is no sign of leaking or smell of oil and i know nobody who's abble to told me what's happened,i realy need help for this problem,thanks

Reply:

Patrice,

Please see

HEATING COST SAVINGS METHODS 

for help with your question.

Start by noticing how much of the time your thermostat is calling for heat - in cold weather and in a building with a high rate of heat loss, the heating system may be acting normally.

Question: moving out, I don't want to fill my oil tank

(Mar 24, 2014) Kathy said:

I have a 275 gallon tank. I am moving soon and do not want to fill my tank. I have a quarter of oil now but was thinking of getting 50-75 gallons. How much would 50 or 75 gallons of oil give me?

Reply:

Kathy,

No one can say with just the information you are giving me, except your oil company who has oil usage data for your home. Give them a call with the question. Alternatively you can ask your heating service technician what oil burner nozzle size (in gallons per hour) is installed on your oil burner.

With that information you could guesstimate by using the calculation I explain in the article above on this page.

It should be apparent that the oil usage rate for your home is going to depend on the outdoor temperature, indoor thermostat settings, and house energy loss rate. Those are data that the oil company factors into a "degree day" calculation for your home.

In real estate this problem is solved by filling the tank completely and charging the new owner/occupant for a full tank of oil.

Comment:

(Dec 19, 2014) sara stout said:

This seems pretty complicated to get a good idea of how long your home heating oil will last.

But once you have gone a couple of months of heating you will have a pretty good understanding. Using that as a starting point you can make a pretty good guess.

Question:

(Jan 5, 2015) Wondering..... said:
I used 189 gallons in 61 days at a constant thermostat reading of 71 degrees F. Assuming everything else is the same, how long would that oil last if I kept the temperature at a constant 74 degrees F?

My previous question was: I used 189 gallons in 61 days at a constant thermostat reading of 71 degrees F. Assuming everything else is the same, how long would that oil last if I kept the temperature at a constant 74 degrees F?
Now assume the heating degree days for the 61 days came to 1500.

I ask the same question but also assume that the heating degree daays increas from 1500 to 1700 for the next 61 day period.

Question: missing shut-off valve on oil line vs. heating oil consumption?

(Jan 12, 2015) Upstate said:

I discovered this year that the oil company that installed my new boiler LAST year apparently forgot to install a shut-off valve between the boiler and the studio apartment (12x15') that is on the same boiler.

The boiler was installed in October in upstate NY, and the problem not reported until the studio tenant moved out in May and I noticed it was 78 degrees in there and the heat was at full blast even though the thermostat was set at 60.

I had the thermostat replaced, thinking that was the problem, and shut off the boiler since it was spring anyway.

This fall, the new tenant reported that it was still heating excessively, so I called in the service technicians. Turns out they 'forgot' to install the valve, and said they wouldn't charge me for the visit to fix it (gee, thanks).

My question is, how much fuel would it have needlessly burned through over 8 months cranking at full bore to heat that one zone?

The oil company is trying to say I owe them $350 for another service call (which the technician -- embarrassed they'd screwed up so badly -- said at the time he wouldn't charge me for). I contend that the amount of fuel burned by their mistake was worth far more than that at an average price of $3.90/gal.

How do I estimate what that might have been? I hate having to use fossil fuels and keep my house at 55 when I'm not here, and 62 when I am here, so the thought of heating a room to 80 degrees for 8 months just makes me sick!

Reply:

Up

I'm unclear on why a shutoff valve would be needed between two areas that have separate heating zones and thermostats.

If a thermostat is not calling for heat then no heat should be delivered to that zone. It sounds more as if there was a thermostat but it was not connected to a zone valve or that controls were mis-wired.

You can get a more accurate answer to this problem by contacting your heating oil supplier, asking them how many degree days were in the period in question, and how much oil your building used. You'll then need to do a heating cost apportionment between the different house areas based on rough gesses on square footage and heat loss rate.

Question: what happened to our heating oil - it just disappeared?

(Feb 11, 2015) what happen said:
I got some weatherized oil last month to bring my level to 3/4.

we have been havin very nippy days and a lot of snow. I cleared off the tank yesturday and saw in a month we lost 1/2 of tank. What happen to all our oil? we left our thermostat at 69 degrees.

Reply:

What

If there is no leak in your oil piping or oil storage tank, then you burned the oil.

Keep in mind that if your tank is like most, it is oval in cross-section. The oil tank level gauge is only really accurate in three positions: empty, half full, and full.

On the other hand a leak in an underground or inaccessible oil tank could indeed step up the apparent oil consumption rate.

Question: does the homeowner have to notify the oil company of a change in oil usage rate?

(May 15, 2015) Stanley Chamrin said:
Homeowner uses residence seasonally and the home is mostly vacant during the winter.

Owner is on automatic delivery and maintains the temperature of the house between 55-60 degF (mostly 24/7) when the house is not occupied. When the house is occupied the temperature is raised to 70 degF.

If the homeowner decides to make this house a full time residence in which the house will be fully occupied during the winter the house temperature will be 70 degF day and 60 degF night.

Does he have to notify his oil company about a change in use so the oil company can make adjustments on their automatic delivery?.

Reply:

Stanley:

"Have to" is a phrase that's harder to answer than "should" - it would certainly make sense for a building owner to inform their oil company of changes that will change oil consumption rate.

If the owner or occupant does NOT do that then the only way the oil company will find out that new information is by receiving a "no heat - out of oil" call (which is not the most convenient for anyone involved) and worse there's the risk of loss of heat and frozen, burst pipes, water damage, and other costs.

On 2019-01-14 by (mod) - oil consumption rate for a vacation home in Dutchess County NY

Jan

The rate of heat losses in homes varies enormously - not just by how good is the insulation but also by how well-sealed the home is against air leaks; in fact air leaks will overwhelm insulation.

The efficiency and state of tune of your oil burner as well as other factors discussed in this article determine how long your oil tank will last.

For example, what's the GPH rate of the oil burner nozzle on the oil burner?

But you can pretty easily get the actual heating oil usage rate for your home from your servicing oil company.

Or if you haven't yet gotten an oil delivery company on automatic delivery give a call to

or the other delivery companies

or a host of others.

We use Bottini and combine oil delivery with a heating boiler service contract.

The oil company keeps track of degree days (factoring in changes in outdoor temperature) as well as the delivery history for your particular home, so that they know when to deliver oil to you on automagic delivery. Just give them a call and you'll be far more accurate than what someone could make up.

Or I can make up a number: in the coldest months of January and February in Dutchess County NY you could easily use up a 275 gallon tank of oil in a month or 6 weeks.

On 2019-03-19 by Jan Cohen

I have an oil heat vacation house I Dutchess county NY that I go to about 2-3 times per month. It is about 2800 square feet, well insulated.

When we are there we set the thermostat to 70 degrees and 58 when we leave.

About how much oil should I need per month?

On 2019-03-13 by dm

how can you go though 150 gals of fuel in a month? Last year it lasted 2 month at 150 gallons of oil

On 2019-01-14 by (mod) - how to guess at how long your supply of heating oil will last

Jean

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.

On 2019-01-14 by jean

We keep thermostat on 74 after buying 100 gal of heating oil. Approx how long should it last??

On 2018-12-20 by Anonymous

Given that you keep your house at 68. If you are away from your house for 8 hours is it more efficient to turn the thermostat down to 62 or to just turn it down to 65?

On 2018-03-24 by (mod) - I had gotten 275 gallons of oil on January 8, 2018. How long does it last

Anon

The answer to "how long will my oil tank last" depends basically on the outdoor temperature, the rate of heat loss from the building, the thermostat settings, and furnace or boiler efficiency. So there is not one single right answer.

The article above and an example calculations given below for other readers describe the steps in calculating how long your specific heating oil tank fill-up can be expected to last.

On 2018-03-24 by Anonymous

I had gotten 275 gallons of oil on January 8, 2018. How long does it last

On 2018-01-05 19:04:26.458840 by (mod) -

38 divided by the oil burner nozzle size in gph gives hours of oil burner on- time. If you have, for example a 1 gph nozzle thats 38 hours of running constantly.

On 2018-01-05 10:27:58.764720 by Bonnie

How long will 38 gallons of oil last

On 2017-12-09 by randi

I had bought 340 litres of oil in the beginning of novemebr I set my furnace at 64 degrees it is now December 9 and I am unable to go home for another 2 weeks due to medical reasons will that oil last until them or am I out of fuel already?

last yyear I bought oil 3 times at 340 litres at a time with my furnace set at 72-78 at times and wol dlast more than a month but beeeeeing I am not home to check I am afraid I am out can I get a general idea pleaee as to what I might be looking at here

On 2017-04-02 by (mod) - Where would the gauge be on a 275gallon oil tank if 160 gallons of oil were to be put in

Donna:

Before adding 160 gallons to a 275-gallon heating oil storage tank, presuming that the delivery driver were to completely fill the tank, the gauge would read just above half-full, or 58% full.

However because drivers, wanting to avoid risk of spilling heating oil, may stop filling the tank the very second that the tank alarm sounds, the tank will be slightly less than 100% full.

In turn, that means that the heating oil tank gauge might have read about half or just slightly below half full before the fill-up.

Remember that these are not precise lab grade instruments and that the tank, being oval in cross shape, will mean that the gauge is accurate only at empty, half full, and full.

Please see OIL TANK GAUGES at https://inspectapedia.com/oiltanks/Heating_Oil_Tank_Gauges.php for details.

On 2017-04-02 by Donna Perry

Where would the gauge be on a 275gallon oil tank if 160 gallons of oil were to be put in

On 2017-03-14 by (mod) - How long 20 gallons of kerosene in my oil tank last

Mariluz and Anon:

Be sure to check out the example calculation in the article above where we take you through, step by step, how to calculate how long any given volume of heating oil should last.

More generally, there is non single right answer and I can't answer your question from just your brief e-text since you don't specify (and probably don't know) the details needed:

The basic factors are:

1. the GPH (gallons per hour) firing rate of the nozzle in your oil burner, where GPH is at an assumed 100 psi - so

2. the psi at which oil is being fed through the nozzle - higher than 100 psi means higher GPH - there are tables for the specifics

3. the number of hours per day that your oil burner runs - or an average per day - typically that's a function of outdoor temperatures (Degree days) tracked by your oil company, AND the specific heat loss rate of your home, so a leaky drafty poorly-insulated home will mean the oil burner runs more often and longer.

4. Those factors give the oil usage rate per day - divide that into 20

On 2017-03-14 by Anonymous

How long 20 gallons of kerosene in my oil tank last

On 2016-10-26 by Mariluz - How long will a 1 gallon of oil last me just for heat

How long will a 1 gallon of oil last me just for heat


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