Fuel cost calculations?

grye

Hi everybody. Is there some sort of fuel calculator that can estimate how much fuel I should be using for the size of my home?

Just realized I filled by 275 gallon oil tank on 12/18 (for almost $500!) and I’m already at 1/4 of a tank. Wanted to see how extreme that was.

Jamie Hall

There's no one size fits all. The fuel used is related to how cold it is and the interior temperature -- the number of degree days for your location is a fair approximation for that; the size of the house and the rate of heat loss (how good is the insulation? How bad are the draughts? etc.); and the efficiency of the heating system.

Needless to say, the answers are all over the place -- even for one structure over time, since the weather related variables (particularly wind) are difficult to quantify with any accuracy at all.

How extreme is your usage? Your usage works out to around 10 gallons per day. I don't know the size of your house. The principle place I care for is 7,000 square feet -- and can quite happily burn more than 30 gallons in a day in this weather.

SeymourCates

@grye

Where are you located?

Size of house?

Type of construction and insulation?

Number and size of windows?


A rough estimate can be offered with aforementioned info. You don't want answers all over the place.

grye

I’m in New York.

House about 1800 square feet.

First floor one large bay window and 7 normal sized. Second floor 6 windows.

Wood frame, attic insulation decent.

SeymourCates

"New York" is a big state (from what I've been told). Need a major airport close to your location.

Also need to know if the oil boiler provides hot water as well as heating? If so, estimate the HW usage per day and advise.

KC_Jones

The lack of main venting is surely costing you money. Every extra minute it takes the steam to get down the main is a minute of wasted fuel.

It may not solve all fuel usage issues, but it's definitely not helping.

bob eck

It has been very very cold outside.
Does your boiler have a coil in it for domestic hot water?
Do you have a indirect water heater with the boiler?
What is the heat loss on your house?
What size BTU boiler is installed?
Is it a new boiler or old boiler?
Is this a water boiler or steam boiler?
Is your boiler cleaned every year? If not cleaned every year the soot sill build up in the heat exchanger and the soot will act as a insulation slowing down the heat exchange and causing you to use more fuel oil to heat the house.
What type of insulation?
New windows or old single pain windows?
How much attic insulation?
Do you have copper or cast iron baseboard?
Do you have cast iron radiators?
If you have CI radiators most likely they are over sized and if they are you should be able to run lower water temps. This will save on fuel used.

KC_Jones

To elaborate if you speed the steam up by 1 minute per call and you have 1 call per hour that is 24 minutes per day. In an average 30 day month that is 720 minutes or 12 hours of burner on time that you would eliminate. If you have a boiler firing at 140,000 BTU that saves roughly 12 gallons of oil per month. In this cold weather you are probably calling for heat more than that.

The above is just a theoretical example to illustrate what main venting can do for you other than improved comfort.

Jamie Hall

@SeymourCates is right -- New York is a big state.

I'm going to guess that since you state "New York" you really mean somewhere south of Poughkeepsie -- folks north of that realise that there is a lot more to the state. If that is so, your usage is not out of line, as a wild ballpark just based on your house size and construction.

grye

Ha ... yes. Sorry. Just north of NYC. It’s been bitter cold, it still just seemed like a lot to me. $500 in less than a month in oil. The joys of owning a home I guess.

Boiler was built 3 years ago. 114,000 btu. Separate electric hot water heater. New windows. Attic insulation pretty good (blown in).

I have to get that main put in, I think it will solve more than one issue. Only problem is it’s exoensive to have someone do it, and I’m weary or doing it myself when it’s this cold out. Too much/expensive heat is better than no heat

SeymourCates

@grye

I utilized NYC-Westchester County Airport as the location for calculations.

For the period commencing December 18, 2017 and ending today, the location recorded 823 degree days.

We are going to estimate your heatloss at 26 BTU/square foot @0°F. We are also going to use a base temperature of 65°F. We make the assumption that you keep the house no more than 70°F. If hotter, the fuel usage is greater and the calculated efficiency (below) is higher.

So, the total BTU required for the period is 14.2M.

We also make the assumption that a properly performing steam system can achieve a system efficiency of 70%.

Therefore, the total amount of oil required for the period is 146 gallons. Your utilization of 187 gallons puts the system efficiency at 55% which clearly shows that the steam system needs some attention if you want to reduce that fuel bill.

Understand that the vast majority of steam systems perform on a similar level as there are typically significant costs involved to effect the highest possible performance from these systems.

Jamie Hall

@SeymourCates -- interesting you picked 26 BTUh at 0 F. The principal place I care for, which is poorly insulated and draughty, has a measured heat loss of almost exactly that, based on the total envelope area (walls plus roof), at -10 F using the gross fuel input to the boiler. The installed radiation has a nominal capacity of 180,000 BTUh output. Since the actual heat loss is rather difficult to measure -- not being an experimental box! -- the real overall system efficiency (that is gross BTU in vs. usable BTU out) is a bit of a fudge, but as best I can determine is around 80% -- somewhat better than the 70% you quote, but not unreasonable.

SeymourCates

@Jamie Hall

I chose the value of 26 based upon experience and the attempt to be conservative with the fuel calculations. If I used 24, the situation would have been more dire for the OP.

Regarding your building, you make a serous error in attempting to calculate system efficiency by using installed radiation.

Since you have provided the square footage of the building, all that is necessary is the location and the base temperature for the structure to calculate the degree days. Once that is accomplished, we can utilize the fuel consumption and the heatloss per square foot to figure the efficiency.

It is highly unlikely that your building achieves a system efficiency of 80%. The best possible combustion efficiency is just about that level and all steam systems suffer losses of a minimum of 10% on top of the combustion efficiency.

EBEBRATT-Ed

One other big issue is that you don't get 275 gallons in a 275 gallon tank. The vent whistle sticks down into the tank several inches to allow for expansion. I used to deliver oil in another lifetime.

Most 275s if you fill one that's empty you usually get somewhere around 230 gallons in it give or take. That changes the equation

I come up with about 8.5 gallons/day. 50,000 btu/hr input.

Sounds reasonable to me

SeymourCates

@EBEBRATT-Ed

Your estimate of 50,000 btu/hr input is reasonably accurate for the building provided the outdoor temperature remained at 0F for the entire time period (432 hours).

Jamie Hall

@SeymourCates . Please. I made no errors in my calculations; I just didn't show all of them. Be a little more generous, perhaps, to others, even if we are just knuckle dragging engineers.

Solid_Fuel_Man

I do not question @Jamie Hall about much, and never about Cedric and steam!

Jamie Hall

Solid_Fuel_Man said:

I do not question @Jamie Hall about much, and never about Cedric and steam!

I dare say I've learned at least as much from you, @Solid_Fuel_Man , as you may have from me!