Cost of 1 million btu's:

Natural gas at $.78/therm, 95% efficient furnace:
(1,000,000 btu / 103,000 btu per therm)($.75)/.95
= $7.66 for 1 million btu.

Heat pump with electricity at $.075 kw-hr, outside temp = 30F (COP = 3)
(1,000,000 btu / 3413 btu per kw-hr)($.075)/3
= $7.32 for 1 million btu.

It is a wash at 30F outside. At higher outdoor temps like 47F (COP = 3.75), 1,0000,0000 btu = $5.90 for the heat pump.

"I just went to the NOAA website and downloaded the average temp for each month last year, here is what I found out. 71 days I could have heated with a heatpump alone, 41 days with only a gas furnace and 51 days would have to be split between the 2 sources."

- I'm not sure how this is figured. The balance point for the house must be calculated. Each house is different. Balance point is based on heat pump btu output (which varies by outside temps), insulation, construction, ductwork, etc.

Dual fuel offers you an option should one of the utilities dramatically change in price.

Good luck.

Additional considerations:

The life expectancy of a heat pump will not be as long as straight a/c because the heat pump will see more wear and tear as it runs in all seasons, not just summer.

Heat pumps put out 97-degree air (at 30F outside) while gas furnaces put out 120 to 130 F degree air.

I have a new heat pump in my all-electric home. I am just trying to give you as much info as I can.

Best to you.

I've had dual fuel since 1995, try to avoid using the 80% gas backup. Since I like it cold, that works well though it will have to come on tonight.

What utilities? I show my last Citizen's bill was 81 cents per therm after taxes and delivery fee was taken off. Add that in which really should, gas is even higher. I think electric is less than your figure but I'm on an old program with IPL because of the heat pump.

A few years ago I switched my neighbors from 65% furnace and 8 SEER A/C to 93% furnace and 10 SEER pump. The first December was much colder than the previous year and yet between the better furnace and the heat pump, gas usage was under 1/2 the previous year.

I'm sold!

The company I work for serves the northern 1/2 of Marion County and Hamilton County if interested.

garyg got the math right. Minimal advantage with the heat pump.I would advise going with the gas system as the heat pump will have limited life due to the extended operation time.

When you posted your Utility numbers, do they include delivery charges and taxes? I'm at $.14/kW and $1.50/ therm. here in the Peoples Republic of New Jersey.

Good luck,

Thanks members
I actually live just north of Indy, and my gas rate I checked with Vectren was
$.78 not including all those extras.

I got the actual high and low temps for each day of 2007, I roughly figured which days the heatpump could run alone (temps between 32-65) and which days it was too cold, and which days the gas back-up would come on for part of it. Not entirely scientific but a rough idea.

How do you figure the COP? and can my HVAC guy give me the balance point of my house pretty easily?

"How do you figure the COP?"
- From the manufacturers technical info. Goodman provides it on their website for their heat pumps. Most mfrs do not provide this info to the public.

"..can my HVAC guy give me the balance point of my house pretty easily?"
- No.

Take care.

In our area, all electric homes with a good heat pump have the lowest overall utility bills. Next would be those with dual fuel. If you figure in $10-20 a month just for the meter plus usage, that fee adds up fast.

As for calculating balance point, a dealer would do a heat loss calculation, which he should be doing anyway. Then he needs to look up the output of the heat pump at various outdoor temps. He plots both lines on a graph and where they intersect is the balance point. Since nobody bothers to do that, we usually guess at 30 to 35 out. If we put in a American-Standard/Trane system, need a higher balance point due to their lower heat output.

I was trying to help a friend with this last fall. He has a dual fuel system -- heat pump with propane gas furnace backup. We found in his case that there would never be a point where the heat pump would be more expensive, so the balance point in this case would simply be whenever the heat pump was not able to heat the house anymore. What he has found in running the system this year is that the defrost cycles largely make the balance point irrelevant: The system goes into defrost, I believe, every 90 minutes, and when it goes into that mode, it will continue to run in backup mode until the thermostat is satisfied. The heat pump will carry it the rest of the time without the inside temp sliding down much. Is that a system that occurs fairly often with systems like this? This is in Kentucky.

prine

There are a few areas like yours that have both cheap electric rates and cheap nat gas rates. I still like the idea of dual fuel for your situation as I suspect the spread between electric and nat gas will widen. I would not purchase a 13 SEER HP. I would move up to at least a 15 SEER with a high COP eff rating around 3. You have to make the decision whether to go with an 80% or 90+% AFUE gas furnace but definitely go variable speed blower. And the previous post brings up the issue of HPs and the defrost cycle. I prefer the electronic demand defrost feature rather than the less eff time defrost. And by all means, include a stat like the Honeywell Vision Pro IAQ that controls blower speed for superior dehumidification when heat pump is operating in cooling mode during the summer mths.

IMO

"What he has found in running the system this year is that the defrost cycles largely make the balance point irrelevant: The system goes into defrost, I believe, every 90 minutes, and when it goes into that mode, it will continue to run in backup mode until the thermostat is satisfied. The heat pump will carry it the rest of the time without the inside temp sliding down much. Is that a system that occurs fairly often with systems like this? This is in Kentucky."

- My 14 SEER Goodman heat pump has time-initiated, temperature-terminated defrost. I have it set to 90 minutes. What I have noticed is that, depending on the outside moisture levels in the air, the heat pump may only be in defrost for a few minutes if there isn't a lot of moisture in the air causing frost on the coil. This short time defrost should not cause a large increase in power consumption using the aux strips.

Take care.

Garyg, yes, if the backup were resistance heat strips then it goes back into heat pump mode as soon as the defrost is complete, right? But on this dual fuel setup, at least on my friend's installation, it stays on the propane furnace until thermostat is satisfied, even after defrost is complete. This might concern the original poster because he is looking at dual fuel. Because the every-90-minute operation of the furnace is enough to make up for any that the temperature has come down if the heat pump has been unable to do the job alone, the balance point in this case is a moot point.

Also, one comment on the original poster's situation. At 7.5 cents per kwh electric and .78 per therm gas, it would seem the only reason to do this is to give yourself flexibility in case of future energy price swings, which may be a very valid reason. But at today's rates, the heat pump at, say, a seasonal average HSPF of 7 (remembering that the nameplate rating is for ideal conditions), the heat pump is going to be operating for, on average, $1.07 per 100,000 delivered BTU versus about 82 cents per 100,000 delivered BTU for the 95 AFUE gas furnaces. Hard to make a case for spending an extra $1,800 to get that.

Thanks again for all the great input.
So... it is recommended I upgrade from the 13SEER pump. Right now my HVAC guy is only doing Lennox, so please don't groan if you knw this isn't the right brand to be using!-perhaps too late!

I'm trying to make a financial decision, so

1) I'm looking at how long it will take to recoup a $1800 upgrade to a 13SEER HP, then

2) if I move up to a 15SEER pump I'm going to guess that will put me upwards of $2500 (since his quote for a 16SEER variable spped a/c unit was $2900)

So after all is said and done, when will I recoup these costs? It may be a wash just to stay with the gas furnace!

"Garyg, yes, if the backup were resistance heat strips then it goes back into heat pump mode as soon as the defrost is complete, right? But on this dual fuel setup, at least on my friend's installation, it stays on the propane furnace until thermostat is satisfied, even after defrost is complete. This might concern the original poster because he is looking at dual fuel. Because the every-90-minute operation of the furnace is enough to make up for any that the temperature has come down if the heat pump has been unable to do the job alone, the balance point in this case is a moot point."

- You are indeed correct. Good point about back-up strips vs gas back-up having to run to setpoint while in defrost. Not fun if you have expensive propane as back-up.

To "Prinesurf":

Your utilities, both gas and electric, are cheap. I see no present advantages going with a heat pump (and I am a heat pump guy, by the way). The only reason to go heat pump is to protect yourself from future changes in utility prices which, as "KY114" states, may be a good reason. It would be something that I would consider.

"1) I'm looking at how long it will take to recoup a $1800 upgrade to a 13SEER HP, then"
- If your gas and electric prices stay the same differential cost for the next 15 years, you will not recover the $1800.

"2) if I move up to a 15SEER pump I'm going to guess that will put me upwards of $2500 (since his quote for a 16SEER variable spped a/c unit was $2900)"
- You will never recover this additional cost no matter what prices do.

"So after all is said and done, when will I recoup these costs? It may be a wash just to stay with the gas furnace!"
- Quite possibly, as long as the difference in utility costs stays the same. But we can't predict the future, only prepare for it.

I do not want to sway you either way, just provide you with enough info to make the best educated decision that you can.

Good luck.

I don't see high SEER paying in this area. I would think getting the 13 SEER unit and putting the $1800 for higher SEER into tightening the house would pay back so much faster. My new sliding patio door was just over $1800, it has made a world of difference in heating & cooling the place over the old one. $1800 would easily insulate an attic if DIY, maybe if done by a pro. Or crawl space. Something besides higher SEER. Another issue, some pumps with higher SEER don't have higher HSPF so the savings is summer and minimal.