How do I calculate heat pump savings?
I need to replace my AC and am thinking about going with a heat pump system. How do I go about calculating the savings from a heat pump?
Currently, I use about 1500 therms per year to heat the house and about 6400 kwh for AC. I live near Washington DC. where we get about 4000+ Heating degree days and about 1500 cooling degree days. Average lows in January are in the 20 degree range. Average lows in April/October in the 40s.
This will give you an idea.
Originally Posted by beenthere
That is a great calculator, and it implies I would save about $1,000 per year. However, I would like to be able to do the calculations myself, because I tend not to trust other people's calculations. (And yes, I do have an engineering background ). Are there any good reference sites which would show me how to do the calculations?
Last edited by jza29970; 06-25-2008 at 12:33 PM.
Reason: add clarity
You can figure the price of 1 million btu's among different fuels and compare them for a percentage of savings.
Originally Posted by jza29970
Cost of 1 million btu's for natural gas at $1.20 per 100 cubic feet, 80% efficient furnace:
(1,000,000 btu / 103,000 btu per ccf) x $1.20 / .8
Cost of 1 million btu's for heat pump with electricity at 12 cents per kw-hr, COP = 3.25 at 35F ambient:
(1,000,000 / 3413) x .12 / 3.25
Cost savings from using heat pump = 25.7%.
Note that below the balance point of the house (32F or so), auxillary heat will be required for the heat pump. This is not included in the calc, neither is the aux heat required for when the heat pump goes into a defrost cycle.
There are no sites that are set up to do an accurate(in depth) operating cost comparison.