View Full Version : nat gas prices...dual fuel or electric?
09-08-2005, 01:34 AM
Low-tech homeowner in northeast kansas, need to replace 15 yr old 3.5T Lennox split system, leaning toward heat pump, so...
- how much more percentage-wise do dual fuel (gas backup) heat pumps cost vs electric backup? is the extra cost worth it? Any brands to stay away from in dual fuel? Our house is fairly well-insulated.
- with gas prices continuing upward, how can straight gas heat, even 92%, compete w/ heat pumps of whatever sort anymore? (our elec rates pretty reasonable in this region) Must be missing something tho cause I don't see a lot of guys saying "switch to heat pumps!"
09-08-2005, 01:53 AM
Originally posted by kojak
Must be missing something tho cause I don't see a lot of guys saying "switch to heat pumps!"
Nope, they are the ones missing something... and it's called SAVINGS! :)
09-08-2005, 08:32 AM
Nat gas prices are spiking due to Katria damage. Electric rates will rise also unless your utility burns coal.
I always feel that nat gas will come back down, but electric rates are never reduced, so I'd choose a duel fuel set-up. If you see sub freezing winter temps, expect electric backup to kick in often.
09-08-2005, 08:36 AM
Is your current system gas or a heat pump with electric backup? There's significant front-end cost in *switching* either way, because of the need for flues/pipes/big electrical circuits to be run. The only path that doesn't have a significant cost that way is going from gas heat, electric AC to dual fuel.
Then you just face the incremental cost of the heat pump over the AC and for a suitable control system to run it. That part isn't bad, though.
If you have an all-electric heat pump now, I wouldn't rush for gas. Gas rates are rising far faster than winter electric rates, and the long-term outlook in that regard is about the same.
09-08-2005, 08:41 AM
Unfortunaltely people recommned what they are comfortable with. Many HVAC Contractors are just as ignorant as to how a heat pump woks and why it costs less to operate. A dual fuel doesnt mean greater savings either and here's why: When your dual fuel system operates below the balance point, the HP will shut off and the gas will take over, I use this in my home and do recommend it. However with a straight HP, your HP still works, and is only suplimented by the amount of electric heat it needs.
For instance if it were, say, 25 degrees outside and your balce point was 28, you would only need to create maybe 1300 btuhs with the back up heat (I am making these numbers up because your load dictates them) but if you had the gas furnace as back up you would be cycling the entire load with gas taking away from the savings the HP offers.
There are people, even on this board who think the auxilliary electric heat comes on in december and doesnt shut off until April and, with that assumption they simply cannot see why HP's are better from a operating cost standpoint.
Jultzya is right, they are the ones missing something.
09-08-2005, 08:45 AM
First of all in order to figure your savings you will need to know what your utility rates are
Then you will need to know the coefficient of performance of the heat pump you are interested in
This will tell you how much you can save
I myself like duel fuel it gives you lots more options imho
And as stated sooooo many times here pick the company not the brand
Because the most important day in the life of your equipment is the day it is installed
09-08-2005, 09:17 AM
Thanks all for the good insights...this forum is really helpful. Doc esp thanks for explaining that HP's keep working w/ electric backup but don't w/ gas backup...never understood that before. I'd think money-wise that could make a pretty big difference.
My quote on a variable Ruud 13.1 SEER unit vs 14 SEER is $550 less (HSPF 8.6 vs 7.8). How do you calculate how long it would take to recup the extra $$ ? Not sure it's worth it...same airhandler.
Thanks for the advice about installers...I have a guy who's really great, knows his stuff, no bs or hype.
09-08-2005, 11:30 AM
I have posted this before, but it fits in with your question. Bear in mind if you use this formula in NE Kansas, and are on Westar Energy, you can get on a different electric rate of about 5 cents conservatively, per KWH instead of the regular 8 cents per KWH.
These are our current rates, fuel oil is a guess since there isn't any here. I just use the current price per gallon of diesel.
On the efficiency calculations, use your own equipment ratings for AFUE, COP and Efficiency.
Converting Fuel to Therms and Comparing Cost
1 Therm = 100,000 Btu
Natural Gas = 1000 Btu/Ft3
LP Gas = 91,500 Btu/Gal
#2 Fuel Oil = 140,000 Btu/Gal
Electricity = 3,415 Btu/KW
Natural Gas is usually priced per CCF (100 FT3) which is 1 Therm. Calculations usually are based on 10 Therms or 1,000,000 Btus (MMBtu).
Example: Typical current natural gas rate of $1.25/Therm will be $12.50/MMBtu.
LP Gas is priced per gallon which is 91,500 Btu. A Therm of LP Gas (100,000 Btu) is 1.09 Gallons.
Example: Typical current LP gas price of $1.25/Gallon will be $1.32/Therm of $13.20/MMBtu.
#2 Fuel Oil
Fuel Oil is priced per gallon which is 140,000 Btu. A Therm of Fuel Oil (100,000 Btu) is .714 Gallons.
Example: Typical current #2 Fuel Oil price of $2.29/Gallon will be $1.64/Therm or $16.40/MMBtu.
Electricity is priced per KWH. There are 3,415 Btu per KW. A Therm of Electricity (100,000 Btu) is 29.28 KW.
Example: Typical current electric rate of $.08/Kwh will be $2.32/Therm or $23.20/MMBtu.
Note for Kojak, plug in $.05/Kwh if considering a heat pump on Westar Energy
Fuel Cost vs. Efficiency
Natural Gas @ $12.50/MMBtu = $12.50/.80* = $15.63
Natural Gas @ $12.50/MMBtu = $12.50/.90* = $13.89
LP Gas @ $13.20/MMBtu = $13.20/.80* = $16.50
LP Gas @ $13.20/MMBtu = $13.20/.90* = $14.67
Fuel Oil @ $16.40/MMBtu = $16.40/.80* = $20.50
Electricity @ $23.20/MMBtu = $23.20/1.0* = $23.20
Heat Pump @47° With a COP of 3.86* = $23.20/3.86 = $5.32
Heat Pump @17° With a COP of 2.36* = $23.20/2.36 = $9.83
*AFUE, Fuel Efficiency or C.O.P.
Using the above formulas, convert to your current rates of Natural Gas, LP Gas, Fuel Oil and Electricity. In some areas, when converting to or adding a heat pump, lower electric rates will apply. Be sure to use those rates in this formula.
09-08-2005, 12:10 PM
Is this KCP&L territory?
Make sure they know you have a heat pump. You will be getting awesome 8-month rates. With a single electric meter, it's 4.3 cents per kwh for the first 1000, and 3.39 cents per kwh thereafter. The remaining four summer months are at the same rate regardless of your heating source and plan selection- 7.36 cents.
Complete rate tarriff in formation is here (5 megabytes!)-
It's big but worth wading through. There are actually a lot of choices available depending on if your water heater is gas or electric, if your space heating is gas versus electric, and if you have one electric meter or a separate meter just for space heating. The relevant stuff starts on page 21.
I wouldn't dream of using gas. These are some of the lowest winter electric rates out there. Based on swany's math, which looks right to me, the heat pump will be cheaper to run except for maybe on the coldest day of the year. Overall, you'll end up ahead skipping gas completely.
Rheem/Ruud air handlers are very smart about using just the right amount of resistance heat and not defrosting more often than is really necessary, which makes them a great choice for a colder climate heat pump. They can also be set up with a "trouble" warning light on the thermostat, which I think is a good idea for all-electric heat pumps. If the heat pump has a problem, in many cases it can be hard to notice because of how seamlessly the electric heat will cover the shortfall- until you get the electric bill and discover that you were using resistance heat all month. With the system able to tell you that there's a fault, you can have it checked out before the electric bill tells you about the problem.
Finally, use a good quality thermostat, and use small setbacks (or no setbacks at all) during heating season when you're asleep or away during the day. With electric backup, you would have to be away for days before the savings of a large setback wouldn't be eaten up by using a lot of resistance heat to get the house warmed up quickly again when you return. Also, the heat pump is at its most efficient during the day when outside temperatures are at its warmest; if you set it back while you're at work, it forces it to run more at night, in colder temps.
It's still not clear whether your old system is gas-electric or a heat pump. If you haven't had a heat pump before, don't be surprised if the heat pump runs for days or more nonstop in cold winter weather. That's just a product of how their heat output drops off as it gets colder outside. Before you worry about how much electricity it uses humming away for such long periods, remember that its electricity consumption also drops off as it gets colder outside, so the math works well for it to run in outdoor temperatures down to around zero degrees F.
09-08-2005, 12:21 PM
Did they quote you the model number of the two proposed heat pumps? There may be more difference between the two than just efficiency (noise, features, etc.). It would help to know the model number of the proposed air handler, too. Post the model numbers here if you've got 'em. We can double-check the efficiency numbers quoted, too. So far I haven't been able to find matches on the spec sheets that seem to fit the numbers you've got.
[Edited by wyounger on 09-08-2005 at 12:24 PM]
09-08-2005, 12:23 PM
Wow!! You guys are tremendous. Sounds like I need to get on the stick, contact Westar, and install that heat pump before the north winds blow. Thank you!!
09-08-2005, 02:52 PM
Sorry wyounger, I didn't see your offer to compare the systems till just now. Here are the model #'s:
14 SEER Ruud HP
13 SEER Ruud HP
UBHK24 J11NFD AirHandler
09-08-2005, 05:00 PM
I must have been editing my post while you were making your last post. That's what I get for always having afterthoughts and editing my posts!
UPPA series has been replaced by UPPB. The difference is largely cosmetic, and it's likely that you would actually get the UPPB when it came to installation. They're probably just working from a slightly out of date sales sheet.
These numbers are fresh from Rheem/Ruud's web site for the air handler you specified.
UPPB042JAZ: 14 SEER, 8.3 HSPF, 78 decibels at the outdoor unit. 33" tall.
UPMD042CAZ/JAZ: 13.2 SEER, 8.65 HSPF, also 78 decibels. 25" tall.
I can't find any other differences to speak of.
09-08-2005, 06:37 PM
Much appreciated. Lots of helpful info, thanks to all.
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