# Thread: calculate cost to heat or cool house

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Originally Posted by doogan123
I am on the final stretch on selecting a HVAC system. As mentioned i have 2 systems competing at this time. On is 25% more than the other. The premium system is a bryant evolution hybrid. I think its a fantastic system. (15 Seer, 11.7 EER The second is a straight hydro Air with AC. Boiler would be a Buderus Propane GB142/30. 94% AFUE

My last hurdle is to determine ( or closely estimate) the operating cost of each and the difference. I am trying to determine how long the payback will take on the premium system vs the Hydro.

Beenthere - To respond to your items ( and hopefully you can help again ) I have compiled the below. I am unable to get everything but i hope its sufficient

Electric Rate - 11 cents/KWH ( Fixed for 2009)
Propane - 2.80
Oil - 3.05
HP Balance point - 32 Deg
Bin Data - not sure what this is - however i got the average Heating degree days - 4804 and cooling degree day - 1190 for my area. Let me know if i need to get something different
Ratings of equipment. I have not identified this. Cannot locate. I have a call into my contractor - however if this helps - the bryant furnace (2) are model # 355BAV042060
The bryant HP (2) are model # 286AWA036000. 15 Seer, 11.5 EER

For the second system - the heating is a buderus GB 142 / 30. First company Air handlers 24MBXB-HW (2)

So - I would love to be able to understand how to calculate the operating costs. What else am i missing to do this?

I have this asked of both contractors - however I need to be able to independently understand how to get this to move forward comfortably.

Thanks guys
Based on your costs for electricity and propane, you should use electric resistance heating for backup and forget the propane.

Your cost for 1000000 btus on propane will be \$45.63
For the same energy w resistance heating \$32.24
For the same energy w an air to air heatpump with a COP of 2 \$16.12

If you go all electric a lot of the electric companies will give you lower electric rates for the winter season which may help even more. Also check for rebates BEFORE you buy anything as they may have specific requirements you will have to meet.

I'm changing my own house over from propane to electric, so all I had to do was plug in the numbers in the spreadsheet I already created. I have a 3200 sq ft home and will save about \$2000 per year. This is enough to justify the air to air heatpump, but not a geothermal, mostly because I can get a \$.04/KW rate for the winter heating season from my utility.

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Originally Posted by beenthere
New York City.

0to5 1hr, 5to10 10hrs, 10to15 26hrs, 15to20 2hrs, 20to25 188hrs, 25to30 330hrs, 30to35 603hrs, 35to40 858hrs, 40to45 838hrs, 45to50 796hrs, 50to55 722hrs, 55to60 745hrs, 60to65 754hrs.

I come up with 145,358,147 Total yearly heating BTUs.
Presuming you set your stat at 70°F.

Its 4009 more if you use your heat when its 68 outside.
Ok - let me use that number. -thanks

3. I'm confused about the boiler. How is this house heated and cooled?
In ny? Use get energy smart. 10% incentive plus tax cred in 09 plus audit for low hanging losses.

Carrier/Bryant infinity is truely mind boggling but \$.

Might be good Acadia hp application, also \$

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Originally Posted by doogan123
Ok - let me use that number. -thanks
lol - it's a little after the fact now - but I was going to suggest using the average of your fuel consumption estimate (2000 gal /yr + 1500 gal /yr / 2) minus estimated hot water heating fuel (200 gal /yr), yielding

(1550 gal / yr) (139,000 btu / gal) (65&#37; everall efficiency) = 140,042,500 btu /yr.

Lucky guess.

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Originally Posted by larobj63
lol - it's a little after the fact now - but I was going to suggest using the average of your fuel consumption estimate (2000 gal /yr + 1500 gal /yr / 2) minus estimated hot water heating fuel (200 gal /yr), yielding

(1550 gal / yr) (139,000 btu / gal) (65&#37; everall efficiency) = 140,042,500 btu /yr.

Lucky guess.
you were pretty close alright - and its all making sense to me now

Let me ask - is conceevable that 145 MM BTU of heat normal for a very well insulated 2500 SQ ft house in NY. Sounds high - but then again - i am not sure what high is....

thanks

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Originally Posted by doogan123
you were pretty close alright - and its all making sense to me now

Let me ask - is conceevable that 145 MM BTU of heat normal for a very well insulated 2500 SQ ft house in NY. Sounds high - but then again - i am not sure what high is....

thanks
Doesn't sound too far out of whack, I guess.

Here's another short-cut metric:

You said your design heat loss was 64,000 btu / hr I think?

64 mbh / 2500 sq ft = 25.6 btuh / sq ft.

Residential structures "usually" have a design heat loss somewhere between 20 and 50 btu's per sq ft. That's a big range - but as you're gathering, there's a lot of variables!

In any event - 25.6 btu / sq ft is pretty good in our area.

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Double post, sorry.

8. Very well insulated house.
R29 walls, R38 attic.

Is that what yours is.

Also, how tight your house is has a large impact on heat loss.

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Originally Posted by beenthere
Very well insulated house.
R29 walls, R38 attic.

Is that what yours is.

Also, how tight your house is has a large impact on heat loss.
New construction, 2*6, Cellulose and foam sealed arround all windows and doors, framing ends etc. Walls will not be R29 - more like R 22. Attic will be R 38 +

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Originally Posted by larobj63
Doesn't sound too far out of whack, I guess.

Here's another short-cut metric:

You said your design heat loss was 64,000 btu / hr I think?

64 mbh / 2500 sq ft = 25.6 btuh / sq ft.

Residential structures "usually" have a design heat loss somewhere between 20 and 50 btu's per sq ft. That's a big range - but as you're gathering, there's a lot of variables!

In any event - 25.6 btu / sq ft is pretty good in our area.
I think from what i am learning from you guys is that for the purpose of my original questions, I can use a given heat loss to calulate the various operating costs. That percentage should be roughly the same for the exact heat loss - am i accurate in that statement?

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I'd say that is correct.

The R value is a linear part of the equation, not exponential or otherwise.

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Those are numbers we would see in a southern city like Atlanta.

You're paying 11 cents/KWH -- that seems low for the Northeast -- what about distribution, franchise fees, etc.

I know for a fact that the former PECO electric in the Philly area was close to 3 times the national average.

Originally Posted by doogan123
THanks - this is the comparison i was looking for.

I just realised that I never posted my heat loss - Sorry it was very late....

Heat loss is 64287 BTU

How did you get to 60 MM BTU - was this just an estimate?. Now that i have posted the heat loss - can this ce calculated?

Thank

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Originally Posted by emcoasthvacr
Those are numbers we would see in a southern city like Atlanta.

You're paying 11 cents/KWH -- that seems low for the Northeast -- what about distribution, franchise fees, etc.

I know for a fact that the former PECO electric in the Philly area was close to 3 times the national average.
emcoasthvacr - Unfortunatly - I cannot challenge the Heat loads at this time, however each one of my 3 potiential installers have said after they get the job, they will share the entire heat load calculations. They did not want to give it out i guess to protect their work - which is fair. I am sure i will have questions here once i see it to ensure its accurate!!

On the Electricity - yes - i am paying .11/KWH and locked in for the year. this includes all delivery, taxes etc etc

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