Home Heating Costs

mtfallsmikey

of a lot of contractors who installed CAC / heat pump systems; quoted their prices per ton!

escaseadjug1793177

How Much does it cost

I am an electrical engineer and I need to make an estimate on home much it costs for heating and cooling a home in New York City.
I am looking for a simple rule of thumb rather than a large equation.
For example, I know the home has 2.5 ton AC unit and 150,000btu boiler.
I was hoping that there is a rough estimate that the AC runs 400 hours a year and the boiler runs XXX hours a year.

Brad White

Had a dart board like that once.

Used Lawn Darts (tm).



What range of accuracy does your client expect?

The assumptions you are starting with are insufficient to make any remotely accurate determination. "System size" is rarely "required capacity". I would even go so far as to say that "system size" is what the required capacity is decidedly not.

It is like deciding the annual electric bill on a building with an 800 A. service. It tells you nothing about demand, connected load, hours of use, living patterns... you could be off by 100 percent and chances are the system was sized by someone you never met. (I do not trust the work of a lot of people I have met!


You really need to know the estimated heating and cooling loads before you can even begin. Otherwise you will give a qualified number with more restrictions than a Westchester Country Club.

For example, using your data, if the 2.5 tons is "accurate" within reason, the home could be anywhere between 875 SF and 1,875 SF if the range is 350 to 750 SF per ton. THAT all depends on glass, primary direction, internal gains, yada yada.

The same square footage could have a heat loss of between 15 and 60 BTUH per SF.

Say the tonnage-based square footage is somewhat reliable, the 150 MBH heating works at 80% efficiency (120 MBH output). the BTU per SF works out to between 64 BTU/SF and 137 BTU/SF- enough of a range that you could give it and be correct if stated as "between these numbers".

Chances are though that the boiler is then over-sized (or cooling is undersized). If grossly over-sized, the efficiency you might assume would be rather low, which raises consumption.

You can see the variables, not to mention the danger of rules of thumb.