So I have 3 years of utility data and I am comparing NatGas vs. Heat Pump.
I am in mid-Atlantic, Maryland an hour south of Lancaster, PA.
For Heat Pump, I know that COP varies with outdoor temp.
However, time of use and temp data unavailable.
If one was to "guess", what would be a reasonable COP to use in a rough comparision. Currently I am using 3.5
So, say 3.1 was correct and I used 3.5, I would be favoring the heat pump?
COP = Co-Efficient of Performance with 1:1 being a COP of 1 or number of units of output for every unit of input. A COP of 3.5 is a higher level of operating efficiency than a COP of 3.1 (note: 3:1 is not 3.1 but rather 3 units of output for every unit of input). Sometimes there is confusion over the different units of measure. BTUhs are used to measure the output of a HP and KWh for units of energy input. Either measure - BTUs or Kw, can be converted to the other for ease of comparison.
interesting that you pick the XL16i, as i am a huge trane fan... it happens to be not very good on HSPF
mchild Quote:
Originally Posted by wraujr
So, say 3.1 was correct and I used 3.5, I would be favoring the heat pump?
COP = Co-Efficient of Performance with 1:1 being a COP of 1 or number of units of output for every unit of input. A COP of 3.5 is a higher level of operating efficiency than a COP of 3.1 (note: 3:1 is not 3.1 but rather 3 units of output for every unit of input). Sometimes there is confusion over the different units of measure. BTUhs are used to measure the output of a HP and KWh for units of energy input. Either measure - BTUs or Kw, can be converted to the other for ease of comparison.
right, it's not 3.1 as it is 3:1. If you would please follow the AOP rules, not that your input here is insufficient or incorret, only professional members with * are allowed to reply. you have the post count to get pro membership and the * if you would like thanks
interesting that you pick the XL16i, as i am a huge trane fan... it happens to be not very good on HSPF
right, it's not 3.1 as it is 3:1. If you would please follow the AOP rules, not that your input here is insufficient or incorret, only professional members with * are allowed to reply. you have the post count to get pro membership and the * if you would like thanks
Pretty sure he isn't in the trade, but is a consumer.
Installed new xL16i (AC) with XV95 NatGas Furnace at end of 2008.
At the time had utility bills on file back thru 2007. At time of purchase toyed with dual-fuel. Decided to just stick with staright NG with AC. But wondered if made mistake based on various discussions on this board. Ended up entering utility data in Excel spreadsheet to track how new system saved on gas and electric. After read discussion on HP, added formulas to compare cost of NatGas used vs. what corresponding HP electric cost would be.
To date, my data shows it has been cheaper to heat my house using NatGas than Heat Pump. The COP is entered in a single cell, so I can change it quickly and see change in graph. Currently using 3.5. To get the graph even for last season, would have to raise COP to 4.
So my experience is that blanket statements made by some that a HP saves money over NatGas are not good. Just saying.. your mileage may vary.
Not really comparing xL16i, comparing using COP of 3.5.
So any heat pump acheiving 3.5 would compare to NatGas as follows
Notable events, after 2008 NatGas prices dropped.
In 2010, switched to fixed rate one year Electric contract which made HP closer, but still not better. Only way to even was COP of 4.0
Point is this is real collected data that shows one thing. It doesn't predict future, etc. But it does show that blanket statements about cost savings and performance aren't good.
Not really comparing xL16i, comparing using COP of 3.5.
So any heat pump acheiving 3.5 would compare to NatGas as follows
Notable events, after 2008 NatGas prices dropped.
In 2010, switched to fixed rate one year Electric contract which made HP closer, but still not better. Only way to even was COP of 4.0
Point is this is real collected data that shows one thing. It doesn't predict future, etc. But it does show that blanket statements about cost savings and performance aren't good.
An average COP of 3.5 is very high. Assuming a median HSPF of 8.5 the average COP would be more like 2.5.
What are the details of the data in the graph? Did you meter the equipment separately? How was the total BTU output determined?
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Originally Posted by wraujr
thanks 
