Which Heat Pump should I use??
I am considering replacing my HVAC system with a heat pump/oil furnace combo system. I already have an oil furnace that uses, on average, around 700 gallons of oil per year to heat (at a locked-in price of $4.09 per gallonfor this year) and a central AC system that was put in around 4 years ago by the previous owner ( I don't know what the SEER rating is for this unit; the furnace is an 11 year old Rheem). I hear that Heat pumps are more energy efficient and my HVAC guy suggested the combo unit of a heat pump operating until a set temp of around 30 degrees and then the furnace kicks in. This seems ideal to me but, he has reccomended two different types. Both are Ruud units but one is a single stage 13 SEER R-410A unit. The other is a 16 SEER TWO STAGE HEAT PUMP ADDS. My house is a 2250 sq. feet bi-level. Most of our living is on the 2nd level. I live in PA. The electrical rate caps are set to expire in about 2 years so my electric will go up, eventually. Currently we spend about $130 per month for electric give or take $25 considering the season.
So, what are your thoughts? Is the 2 stage a better option? I think either will pay for itself in time. Just what is the better option based on my situation? Thanks for all of you who respond!
Last edited by volpone1a; 08-01-2008 at 01:28 PM.
Without knowing your KWH cost, I think your HVAC guy is right that an HP will save you down to around 30 degrees, especially with per gallon cost like that. Its hard to estimate how much of a savings, so see below.
Since you didn't mention tonnage, how did the tech size these HPs?
I suggest you verify the btus of those units to be certain you're comparing apples to apples. If you check a number of posts here you'll find that sometimes the units aren't always the same BTU output.
Check out this heating cost comparison calc. It may help you mix and match different types of HPs with your oil furnace as backup versus just your oil. Its not perfect, but you can personalize the numbers for your application to give you a ballpark. I'm no expert so I stress the ballpark part. This spreadsheet requires you to estimate usage of your system, so play around with best and worst case scenarios.
You can estimate a 14 SEER or 15 to see where your sweet spot is in long term payback.
Thanks for your reply. My electric rate is, on average, 2.70 cents per KwH. I tried to use your calculator but I could not figure it all out. Maybe I didn't enter the right info. I didn't see my possible system on there, either. Some of the anual energy costs for thos e systems were at over $27,000.00 !! What was I doing wrong?
I don't know of any place in PA that pay 2.70 a KWH.
Most areas average $0.105 a KWH delivered.
Since your oil furnace isn't a VS blower, I would recomend just getting the single stage heat pump.
Our electric will go up in 2010, but oil isn't going to be any cheaper then it is now either.
According to my bill, cost per KwH is around $0.270, on average. I agree, that oil won't get any cheaper and I think that a HP would be more economical. From what I have been able to discern, doesn't a 2 stage use less electricity by only pulling full electric load when the demand for either heat or AC is greatest? (like on a 70 degree day only one compressor or coil will run and on unusually hot or cold days both will run as opposed to a single stage running all of the time to maintain set temp.?) I admit, that I am a novice at all this but I would like to make the best decision I can. Thanks for all your help! I live in New Cumberland, near Harrisburg, by the way.
Take your electric bill. Divide your KWs used by the cost. And that will give you an idea of how much you pay including all delivery and taxes.
Rheem uses Scroll unloading compressors. So you will have only one compressor.
Your indoor coil, unless custom ordered(unlikely) won't be a split coil.
So when running in first stage, the entire indoor coil is used. So since the blower can't slow down much, the coil will not be very cold, and won't remove much moisture, so you will end up with a high humidity. Which could make you have to set the stat lower to feel as comfortable.
In heat, when its in first stage, the air will feel cool coming out the registers even when its 50° outside. Which can make you feel cold, so you end up turning the heat up higher.
You will be better off with the highest efficiency single stage heat pump you can get.
Then a 2 stage unit with a standard blower.
This is the answer to the single stage / dual stage compressor question.
Originally Posted by beenthere
I would also check into a 14 SEER heat pump. Sometimes the 14 SEER provides a higher EER (Energy Efficiency Ratio) and HSPF (Heating Seasonal Performance Factor), even with a non-vs air handler motor.
If you post the model numbers of both the condenser (outside unit) and matching indoor coil, someone can check the performance and btu numbers for you.
Last edited by gary_g; 08-01-2008 at 05:14 PM.
Reason: Added 14 SEER comment
Okay, so you're definitely doing something wrong. It took me a while to reconfigure this spreadsheet to my tastes, but then I do this type of stuff all day long.
Originally Posted by volpone1a
First, enter in your data up top, house size, heat loss, heating degree days (most likely less than 9000). Check some weather sites to get this number.
Next enter in your KWH costs in G9 and G10 of 0.27 if figured correctly from beenthere's advice, and then heating oil. Look at the bottom where heating oil is, enter or estimate your efficiency and then play with the house size, heat loss, etc. to get the usage close to your annual gallon usage. You can then play with this number for best or worst case winters.
The last block, 'Cold Climate Heat Pump with Fuel Oil' you can use for you new system. Change the efficiencies in column D,E. For a 13 SEER maybe put in 160% to 210%. If you have the COP curve on your proposed system you can put in actual numbers. Finally, note the calculations in column F contain a weighted average usage of the two pieces of your system. The optimistic writer of this spreadsheet (who was trying to sell cold climate HPs) thought their HP would run 95% and the backup heat 5%. Change those to what you think - say maybe 70/30, 60/40 or 50/50 HP/Oil. Others might have some idea how much each of those systems will run in your climate.