Annual Heating Cost

Art M.

If I know what my heat loss BTU's are, can I roughly calculate my total consumption of fuel, be it gas, oil or electricity?
If so, what is the formula.

Thanks

J.C.A._3

You'll also need...

The number of degree days to figure this out. Try NOAA or The National Weather Service to find this for your area.

I know there is a formula, but can't bring it to memory....It's Friday. Good luck. Chris

Brad White_56

DD Formula

Heat Loss (BTUH) x Degree Days x 24 (Hours)
______________________________________ xCd factor**

Delta-T* x Efficiency of Plant x Fuel Units

Where:

* Delta-T referred to is the design Delta-T used to calculate the heat loss,

** The Cd factor is a variable which accounts for solar and internal gains and is based on degree-days in your area. Typically for the 5500-6500 degree-day areas this is about 0.60 to 0.63

Degree days can be the normal 30-year average for budgeting or over a given year for specific targeting.


Here is an example:

House with 75,000 BTU heat loss, 6,000 degree-days, 70 degree design Delta-T and 85% (0.85) plant efficiency using gas at 100,000 BTU's per therm:


75,000 x 6,000 x 24

_________________ = 1,815.13 therms (gross)


70 x 0.85 x 100,000

x Cd of 0.60 = 1,089 therms net for the year.



If you are using oil, use 138,000 BTU's per gallon.
If you are using electricity, use 3,413 BTU's per kWH.
Efficiencies vary of course.

Naturally you multiply the fuel units used by the cost which also varies.

Hope this helps.

Brad

Bill Nye_2

fuel cost

It depends. It depends on where you live, how your home was built, how many kids you have [they "never" leave the door open] If your wife works, if she is home in the day time if she turns the t-stat up. Or if your kids crank it up when they get home from school.

It depends on how you make your hot water, how comfortable you keep your home. How much solar gain. How the system was installed. Insulation ? many factors.

Mike T., Swampeast MO

If a condensing/modulating boiler is in this comparison, you'll have a problem making comparisons with any other form of boiler. AFUE will NOT be a reasonably accurate efficiency predictor for a condensing/modulating boiler provided that it's properly installed/controlled in a well-suited system.

If your needed supply temperature maxes around 140F AND you have proportionality either via mass (think highly conductive radiant floors/walls/ceilings) or control (TRVs/FHVs/Pneumatic) use 140%-150% efficiency based on a Manual-J calculation--seriously...