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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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
Here is an example using some sample numbers: 100 gallons of oil in the oil tank and a 1 GPM oil burner nozzle.
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.
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
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 / multifuel stoves.
eireheat [dot] com provides a nice description of vaporizing heaters from Nestor Martin (Belgium). We excerpt:
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:
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!
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Frequently Asked Questions (FAQs)
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
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.
3/23/2014 cass said:
"Here is an example using some sample numbers:
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!
Thanks Cass, I have corrected the math. We appreciate your careful reading and your taking the time to comment - working together makes us smarter.
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.
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?
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:
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..
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 links along the left of this page near the top 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
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
Patrice, near the top of this page in the article links at page left click on
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?
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.
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