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Old 01-03-2012, 11:50 AM   #1
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a/c or heat pump?


Our a/c and furnace are over 20 years old, our a/c bills are huge, and every year we have to have the a/c serviced at least once, the furnace has been starting to act up too. So it's time for something new, but I'm trying to do some homework and find out what system I want. A new natural gas furnace and a/c, or a heat pump. I've heard heat pumps have come a long way and work well at cooling, their seer rating isn't too far from an efficient a/c. I can't find any real new information on heat pumps though besides for heating a home in the winter. I'm not worried about winters, we live in california in zone 9, the winters don't get below 30 most times, but during the summer it can be in the 90's for a couple weeks.

Currently our furnace was built in '88 and has a 71,000 capacity. Our A/C was built around the same time and from what I can gather is a Carrier 3ton. I believe it was a 10seer at the time, and heard a/c's drop a seer every 10 years on average? Model #38th036300 Our home is 1700 sq ft, 2 story, a lot of windows, two sliding glass doors on the north of the house (which we hope to change soon, why do we need two, really?! lol). PG&E supply all of our electric/gas, kwh is $.20 and the therm is $1.04. Our bills total in the winter are around $100-200 and in the summer reach up to $400 per month.

If I go with a furnace a/c I am planning (if finances work out) at least a 95% efficient furnace and no less then an 18 seer a/c.

So with all of that information what do you guys think? Or even if you just have more information then what I've found about heat pumps that would be awesome!

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Old 01-03-2012, 12:05 PM   #2
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a/c or heat pump?


Quote:
Originally Posted by Dwillems View Post
Our a/c and furnace are over 20 years old
the furnace ('88 and71,000 capacity) has been starting to act up too.
So it's time for something new <-- Agreed

trying to do some homework and find out what system I want.
A new natural gas furnace and a/c, or a heat pump.
If you have natural gas it will almost always be the best default option.

Quote:
I'm not worried about winters, we live in california in zone 9, the winters don't get below 30 most times, but during the summer it can be in the 90's for a couple weeks.
Even in California, if you have natural gas...

Quote:
Our home is 1700 sq ft, 2 story, a lot of windows, two sliding glass doors on the north of the house
Get at least two contractors to calculate your heat loss and prescribe an equipment package. Go from there in making the choices.

hth

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Old 01-03-2012, 12:06 PM   #3
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a/c or heat pump?


Sounds like you are thinking in the right direction with the new heat pump. The only way you would be better off is to go with a geothermal heat pump. This would eliminate your carbon footprint and pay for itself in savings (if you have room for the wells or loop in your yard and are planning on staying where you are a while). They are more expensive upfront but with the tax rebate you are looking at a pretty quick payback. Good Luck!
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Old 01-03-2012, 12:44 PM   #4
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a/c or heat pump?


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Originally Posted by Dwillems View Post
PG&E supply all of our electric/gas, kwh is $.20 and the therm is $1.04.
I pay about 0.10/kwh and 0.80/therm and I have dual fuel (heat pump with natural gas aux). With your electric costs, I would forget the heat pump and go straight AC. Unless your costs drastically change, the ROI isn't there.

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Originally Posted by TarheelTerp View Post
If you have natural gas it will almost always be the best default option.
No. It depends on the local cost of elec and gas.
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Old 01-03-2012, 01:00 PM   #5
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a/c or heat pump?


If you have natural gas it will almost always be the best default option.

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Originally Posted by garya505 View Post
It depends on the local cost of elec and gas.
Yes, the relative cost of electricity is an example of why this is so.
With a very few exceptions (in the US) therms will almost always be less than KwH
There are other factors too.

hth
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Old 01-03-2012, 03:06 PM   #6
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a/c or heat pump?


Quote:
Originally Posted by TarheelTerp View Post
If you have natural gas it will almost always be the best default option.



Yes, the relative cost of electricity is an example of why this is so.
With a very few exceptions (in the US) therms will almost always be less than KwH
There are other factors too.

hth
I disagree that it's "almost always" and there are "very few exceptions". Local climate matters too. A heat pump is very efficient at the moderate temperates found in the southern states, and in spring and fall in most states. In many parts of the US, at least for part of the year, you can heat with a heat pump cheaper than natural gas. It can also be more comfortable as it's usually a lower heat rise and longer run times.
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Old 01-03-2012, 03:11 PM   #7
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a/c or heat pump?


Spent most of my life in California. When we lived by Yosemite, we either had a choice of heat pump or propane and with the high power rates in California, both were very expensive to use.

I can tell you right now, if your paying 20 cents a kwh, the only way to go is with natural gas, no reason to even consider a heat pump.
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Old 01-03-2012, 03:22 PM   #8
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a/c or heat pump?


Quote:
Originally Posted by Dwillems View Post
Our a/c and furnace are over 20 years old, our a/c bills are huge, and every year we have to have the a/c serviced at least once, the furnace has been starting to act up too. So it's time for something new, but I'm trying to do some homework and find out what system I want. A new natural gas furnace and a/c, or a heat pump. I've heard heat pumps have come a long way and work well at cooling, their seer rating isn't too far from an efficient a/c. I can't find any real new information on heat pumps though besides for heating a home in the winter. I'm not worried about winters, we live in california in zone 9, the winters don't get below 30 most times, but during the summer it can be in the 90's for a couple weeks.

Currently our furnace was built in '88 and has a 71,000 capacity. Our A/C was built around the same time and from what I can gather is a Carrier 3ton. I believe it was a 10seer at the time, and heard a/c's drop a seer every 10 years on average? Model #38th036300 Our home is 1700 sq ft, 2 story, a lot of windows, two sliding glass doors on the north of the house (which we hope to change soon, why do we need two, really?! lol). PG&E supply all of our electric/gas, kwh is $.20 and the therm is $1.04. Our bills total in the winter are around $100-200 and in the summer reach up to $400 per month.

If I go with a furnace a/c I am planning (if finances work out) at least a 95% efficient furnace and no less then an 18 seer a/c.

So with all of that information what do you guys think? Or even if you just have more information then what I've found about heat pumps that would be awesome!
If you can afford it, a ground source geo-thermo heat pump would be the most cost effective over the long term, its worth looking into.
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Old 01-03-2012, 03:40 PM   #9
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a/c or heat pump?


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Spent most of my life in California. When we lived by Yosemite, we either had a choice of heat pump or propane and with the high power rates in California, both were very expensive to use.

I can tell you right now, if your paying 20 cents a kwh, the only way to go is with natural gas, no reason to even consider a heat pump.
FWIW ...

The only place I'd consider going straight heat pump would be maybe Florida (or maybe southern AZ and CA).

For all other areas, if the only gas I could get was propane, I'd go dual-fuel. If I had natural gas available, I'd look at the cost of electric and natural gas, then decide between 1) gas furnace and AC, or 2) gas furnace and heat pump (AKA dual-fuel). At 0.20/kwh this is a no-brainer and I wouldn't even waste my time calculating the balance point.
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Old 01-03-2012, 04:14 PM   #10
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a/c or heat pump?


A geo would have to operate at a COP of atleast 5.4 to be 7 cents cheaper per 1,000,000 BTUs of delivered heat. And would take a long long time to pay itself back, let alone save the OP any real money at his utility rates.

On the cooling side he could save some real money. But may not get a ROI for 15 years or more depending on type of geo.
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Old 01-03-2012, 04:19 PM   #11
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a/c or heat pump?


Dwillems. Make improvements to your house first. Air sealing, add insulation where possible. Get rid of that extra sliding door.

You may be able to reduce your heating and cooling equipment size substantially. Good chance your duct system is under sized for the size equipment you currently have. Reducing required equipment size will help to correct this. And automatically help with reducing your energy cost.
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Old 01-03-2012, 05:33 PM   #12
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a/c or heat pump?


Quote:
Originally Posted by garya505 View Post
FWIW ...

The only place I'd consider going straight heat pump would be maybe Florida (or maybe southern AZ and CA).

For all other areas, if the only gas I could get was propane, I'd go dual-fuel. If I had natural gas available, I'd look at the cost of electric and natural gas, then decide between 1) gas furnace and AC, or 2) gas furnace and heat pump (AKA dual-fuel). At 0.20/kwh this is a no-brainer and I wouldn't even waste my time calculating the balance point.
Straight heat pump works great here in southern Nev also, we are straight heat pump and although electric is starting to creep up, I can still keep the power bill in line with the neighbors electric and gas bills combined.

If the power rates get too much higher, I may throw a gas unit back up there.
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Old 01-03-2012, 06:40 PM   #13
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a/c or heat pump?


Wow, thanks for all of the great replies! I really do want a geo heat pump, but it's not beneficial enough to us right now. My wife and I are both military and don't plan on staying here long enough for that kind of pay back. I'm not even positive a traditional ac will, but it's something I think we need to do and it will help sell the house faster when that time comes.

In the mean time I've slowly been trying to do other things to the house to help. None of the ducts were even attemted to be sealed, so I taped all of them up as I could with the aluminum tape. Including where they meet the register, and I sealed the vent to the drywall with caulking. I've also been going around trying to seal up as much I can around the house. I'm looking into getting an energy audit to help me prioritize my work (are these really worth getting done?)

I know I need more insulation in the attic and maybe more roof vents. All we have now is two gable vents with one temp controlled fan blowing out the front of the house. I'm thinking of moving it to the back though. We get strong winds here a lot and it hits our front head on so the fan fights the winds. Why not move it to back, locking the front vents open, and have them work together?
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Old 01-05-2012, 11:56 AM   #14
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a/c or heat pump?


We live in Kentucky the electrical rate is .08 per kw. Our old natural gas furnace (90% efficient with 9 seer AC) and central air needed replacement (average cost to run about $150 to $200 per month to heat and cool, worst bills were $310 and $304 during the coldest months, electric and gas combined). Switched to a closed loop geo-thermal system (4 200' wells) with water heating also. Total system cost $ 13,400.00 (without 30% tax credit figured in). My highest bill in two years has been $98 with averages of $67 to $79. Our water temp from the wells averages 57 and we have 2100 sq. foot ranch with full basement (3/4 finished) built in 1973 with R13 insulated walls, R30 attic and brick facade.

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