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# calculating actual heating costs

#1
05-25-15, 07:58 AM
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Join Date: Apr 2008
Location: Massachusetts
Posts: 95
calculating actual heating costs

Ok my Son might buy a brand new freshly built home. It has R48 factor insulation in the ceilings and is supposed to be inexpensive to heat....BUT it has propane heat, and stuff isn't cheap here in Southern New England. ALL the new homes in this area are going this route and the building contractors are being adamant about not swapping out to oil. And, their was a brief mention of some sort of 'contract' the new homer gets 'tied to' with a supplier HE does not get to chose AND no other supplier will fill your system if you attempt to go with another supplier! That is what my Son was told.

We can't get a total gallons of propane to be used per year for this new home, so he can't accurately calculate how expensive it will be to produce 1 million BTU's of energy. Travis Industries puts out a worksheet to do the calculating and comparing of all kinds of fuel, all you need is the cost per unit. BUT that does not tell me how many of these units I will use.

He could use my usage but this new home should be much more efficient than my home is...but how much more efficient will it be?

Now I found a guide put out by eiadotgov states that the average 1500 sq ft home in NE will use 109,000,000 BTU's of energy. BUT in my current home built in the late 60's which has had many upgrades like duel pane windows and 8" bats of insulation added in the loft I only consume 72,840,000 BTU's of energy to stay warm.

How ta heck can he get an actual number he can believe about the BTU demands of a given home design? Does he have to find a current home owner and ask them if they have lived there a year, and how many gallons of propane they used??

BTW I am also asking that now for any new 1500 -2000 square foot home.

#2
05-25-15, 12:27 PM
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Join Date: Oct 2008
Location: New England
Posts: 9,457
There is a classification of energy auditors caller HERS Raters who can take a set of drawings and give you an estimate of the expected energy use. BUT, it all depends upon the builder and sub-contractors. If they are experienced in building energy efficient homes, that average 109 million btu number could be cut by 75%. In oil terms (I live in oil heat country) we estimate a yield of 100,000 btus per gallon, so they are saying 1,090 gallons is average, sorry not even close. A new 1,500 sq ft home in Southern New England should be easily heated with 30 million btus (300 gallons of oil) and if great attention to energy efficiency were used it could be far less. The good news is that those energy efficiency details are not all that expensive, like good air sealing.

If you have the details on the house, like wall thickness, window area, basement exposed to the weather, and number of stories I can run the basic numbers for you. There are also heat load calculators available online if you want to dig through it yourself.

But, a HERS Rater would pack some persuasion when it came to telling the builder what standards e/he needs to meet. Example, the quality of the installation of the insulation gets a grade, basically how neat they were. If the house uses forced hot air, then the ducts are tested for air leakage. When completed the house should meet some predetermined air tightness level.

My guess is, if you start talking any of these improved efficiency measures you will either find out they know what they are doing, or they will refuse to follow your advice, which would mean they don't know what they are doing.

Determine what energy codes that area is following, IECC 09 or other. International Energy Conservation Codes.

Bud

#3
05-25-15, 01:02 PM
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Join Date: Mar 2006
Location: Wet side of Washington state.
Posts: 16,321
Now I found a guide put out by eiadotgov states that the average 1500 sq ft home in NE will use 109,000,000 BTU's of energy.
Energy usage is not the same as energy used for heating. That figure may very well include electricity used for anything and everything from refrigerators and kitchen ranges to air conditioning, Nintendo games and Internet modems.

I think that Bud has given you excellent advice, especially when it comes to how well the builder pays attention to details. The gross amount of insulation in a house is nowhere near as important as the care taken in sealing air leakage and properly installing insulation.

#4
05-25-15, 02:37 PM
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Join Date: Apr 2008
Location: Massachusetts
Posts: 95
Hello Bud9051 & Furd!
Thanks for the quick response. Bud9051, you have given me some great details but the home is already built. I will look online and see if I can locate a heat load calculator online. Do you have a link to any that are accurate? Based upon what the builder will tell him about the home's innards we may very well be able to get what we are seeking. Not necessarily to the dime cost but get me within \$3-500 of what I might expect it to cost.

Furd I think you are right about the BTU load. We figured out today after lunch that the BTU load of 109M BTU;s has to be the TOTAL amount used not simple the amount necessary for heat.

My 72.8M BTU use was based on my exact oil usage only and me home is not nearly as well insulated as these new homes are even if they skimped a bit here and there during the build. BUT in Mass inspections are at every step of the build so it is easier to do it once right then do it over again.

#5
05-25-15, 04:08 PM
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Join Date: Mar 2006
Location: Wet side of Washington state.
Posts: 16,321
There are lots of heat loss/heat gain calculators available on the Internet. Some are free and most have a fee, either a limited time usage or a complete program. The free ones are worth every penny of their cost but they do serve a purpose in showing a halfway decent guesstimate. Biggest problem is that they often so over inflate the requirements as to make them almost useless for real-world results. One popular calculator which is otherwise very good overestimates by about 20% the heating requirements.

One product, a three month trial for \$49, is often mentioned by people that have used it as being the best fifty bucks they have ever spent. I personally have only done heat loss calculations using the manual method and that was some forty years ago. The biggest problem you might find in using them is that they are going the other direction from what you want, i.e. they are for calculating the needed size for a furnace or boiler and then the size of ducts or pipes to terminal units for maximum comfort and economy. In your (your son's) case the equipment is already in place and you want the operating costs. This add a step or two to the process.

Even asking others what they spend for heating is problematic. No two households will have the exact same lifestyle and that alone can skew the results significantly. Some people never adjust their thermostats and either add layers of clothing if cold or open a window if hot. Others try to micro control their homes to a half-degree throughout the entire house. Kids (or cats) running in and out will cause a higher usage than will a single adult that stays indoors and only opens the door a couple of times a week.

So if your son is able to ask people in the area have him remember that the true costs will will be +/- about 20% and that "comfort" is a moving target with lots and lots of variables driving it in either direction. Remember also that people often don't have a clue as to what it costs to heat (or cool) their homes and that ANY figure given is subject to interpretation.

#6
05-25-15, 04:33 PM
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Join Date: Oct 2008
Location: New England
Posts: 9,457
I have also done most of my energy calculations manually, but when I have to do many runs to adjust variables the closest calculator for my needs has been from the Builditsolar.com web site. It uses the basic sum of loss through all 5 major areas and adds no margin as some calculators do, just heat loss. I will at least get you familiar with where the heat is going. Take a look and if you need help filling in something like air leakage we can give you default numbers.
file:///C:/Users/Home/Documents/My%2...c/HeatLoss.htm

Bud

#7
05-25-15, 04:45 PM
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Join Date: Apr 2008
Location: Massachusetts
Posts: 95

Again we appreciate this very much.

Buying a home is a big decision. Today heating costs have to be considered.

#8
05-25-15, 04:58 PM
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Join Date: Apr 2008
Location: Massachusetts
Posts: 95
Don't bother! I found the site!

#9
05-25-15, 05:01 PM
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Join Date: Oct 2008
Location: New England
Posts: 9,457
Sorry, I have that copy on my pc, but had both open, just grabbed the wrong one. Here is the web link:
Home Heat Loss Calculator

Gary runs that web site and you can copy this calculator. He had to help me activate it as you can tell I'm a computer idiot. Maybe challenged would be a better word.

Bud

You were faster than I am.

Last edited by Bud9051; 05-25-15 at 05:03 PM. Reason: addition
#10
05-25-15, 06:58 PM
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Join Date: Apr 2008
Location: Massachusetts
Posts: 95
Thanks!! It looks this site has quite an amount of information. Much appreciated.

#11
06-14-15, 07:46 AM
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Join Date: Apr 2008
Location: Massachusetts
Posts: 95
Update on this issue AND a simple solution

Ok, I had a brain fart a while back about how can figure what it would cost to heat a given home with a given fuel. IF you own your own home or know someone who does there is a history of fuel used for that home.

All you need to know is how many BTU's does this current home need to heat it!

We already know how many BTU's of natural gas are used in my Son's home. Now we just needed to convert his current home to propane by figuring how many BTU's of propane he would need to heat it!

Then we calculated the cubic footage of his current home to get a number of BTU's used for each cubic foot of space in his current home.

Next was figure out how many cubic feet were in any new home he may look at that has propane as a fuels source.

The only 'guesstimate' part was how much more efficient were the new homes over his older late 80's home. He often hears they are 50% better but that might be a bit of 'salesmanshipspeak' if you know what I mean.

Even if they only use 60% of the fuel he currently uses, the cost of propane isn't that important a factor as how much propane he needs to buy, to create the BTU's he needs to keep one of these new energy efficient homes heated!

#12
06-14-15, 08:22 AM
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Join Date: Oct 2008
Location: New England
Posts: 9,457
It is hard to accurately predict what a new home will require based upon your approach and that is why many people are pushing to make an energy audit a mandatory part of any purchase and sale of a home. That requirement is in effect in some areas, but "everywhere" will take a lot more time. However, that option is always available, just a question of getting the seller to agree and who pays for the audit, technically called a rating.

A rating doesn't just look at the volume of a home, it looks at the windows, walls, floor, ceiling, foundation, and air leakage, and includes many other smaller details, like solar and wind exposure. If a builder or real estate sales person is pushing their claims about the home being energy efficient, ask them to show you the energy rating. Don't settle for some simplified energy audit, you want to see a HERS Rating, it is the standard. If their claims are valid they should welcome having one done. If it is just 'salesmanshipspeak' they will not. People in the energy efficiency field refer to it as the MPG for homes.

Bud

#13
06-14-15, 02:03 PM
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Join Date: Mar 2006
Location: Wet side of Washington state.
Posts: 16,321
I agree with everything that Bud has written.

If you just want to compare different fuels on a cost-to-BTUs basis here is the calculator.

Warmair.com - Fuel Cost Comparisons