thevinmanfxst
New Member
Posts:36
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| 01 Jan 2009 08:10 PM |
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Hey guys,
I have a new 5 ton DX system heating a 3000 sq ft, 2 zone house in New England. (I also have hot water generation & no aux heat) My house is pretty new and well insulated. We keep the temp btw 68 & 72 most of the time. I don't have any fancy gizmos hooked up to measure performance, but I did notice a huge increase in my electricity bill. Was wondering if I should be concerned...or take further steps to measure or address.
Here is the deal: I took a look at last years electricity bill (for Nov 6 - Dec 11) and my usage was 1388 Kwh. Last month's bill for the same period (but with my geo system running) was 2815 Kwh. I have not made any other huge changes in my electricity usage...which tells me my geo system used roughly 1427 Kwh *.18 = $259.04!!!
Does this sound close/right or is there something seriously wrong with my system? (I'm dreading to see Decembers hit...) |
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engineer
Veteran Member
Posts:2749
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| 01 Jan 2009 08:31 PM |
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FWIW down here in North Florida this November was as cold as a typical December.
How did you used to heat the house? how much fuel did it use?
Unfortunately your electricity cost at $0.18 is nearly double national average.
1427 kwh / 35 days = 40 kwh / day. A 5 ton system might use 3.5-4.0 kwh / hr, so it could be running 10-12 hours / day. That seems a bit high for early winter, but maybe not since it can run for hot water only. How many live in the house? Any teenagers taking 20+ minute showers? |
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Curt Kinder <br><br>
The truth is incontrovertible. Malice may attack it, ignorance may deride it, but in the end, there it is - Winston Churchill <br><br><a href="http://www.greenersolutionsair.com">www.greenersolutionsair.com</a>
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thevinmanfxst
New Member
Posts:36
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| 01 Jan 2009 08:50 PM |
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Ah, Florida. Sounds nice right about now...(14 F outside at the moment). And yes, the cost of living here in CT sucks in general. Everything is way too expensive...
I used to use baseboard oil. Last year I used 1010 gallons for the entire year, including hot water. (From my delivery stubs, I used about 700 gallons btw December and March) Three people live in the house, just my wife, my 15 month old daughter, and me. None of us take extra ordinarily long showers. (I still have a few years left before dealing with teenager energy usage issues!) |
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geo fan
Basic Member
Posts:408
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| 01 Jan 2009 08:51 PM |
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Are you on the CL & P VPP rate , if not have you looked into it?
Whats you basement zone kept at?
Whats the home kept at
Where our issues on last months bill?
Hows the water?
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thevinmanfxst
New Member
Posts:36
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| 01 Jan 2009 09:09 PM |
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I have looked at the CL&P VPP rates, but haven't had a chance to do the estimations. You think its worth it?
My basement zone is kept at 68, the upstairs at 70, most of the time. (My daughter had a virus last month and we jacked it up to 72 upstairs, for her, for a week or so.)
Yes, our issues with the hot water system were in November. So for about a week, my hot water system was turned off. But, the water is working good now. Very comfortable....109 on the lower temp sensor on the tank, so pretty hot coming out of the tap. (Not to get off topic, but the solution for that issue (high pressure switch trip) appeared to be solved by adding a few more lbs of refrigerant, and adjusting the temp delta on the HW system a little...not sure if that matters.) |
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engineer
Veteran Member
Posts:2749
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| 01 Jan 2009 09:15 PM |
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OK, let me do some math on this one. Absent better data, I'll assume same heating load as last year, i.e same weather and occupancy. It helps that both new and old systems handled hot water
Suppose last year for the period in question you burned 200 gallons of oil at 85% efficiency. That works out to about 22 million Btu heat delivered to space and water. 1427 kwh electricity is about 4.9 million btu, so assuming same heat load you experienced a COP of 4.5. That's very good performance. Tuffluckdriller, our resident DX cheerleader will be along within the day to applaud your coice of a DX system
If you can refine my assumptions about the weather and heating oil burned and efficiency I can rerun the numbers |
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Curt Kinder <br><br>
The truth is incontrovertible. Malice may attack it, ignorance may deride it, but in the end, there it is - Winston Churchill <br><br><a href="http://www.greenersolutionsair.com">www.greenersolutionsair.com</a>
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geo fan
Basic Member
Posts:408
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| 01 Jan 2009 09:30 PM |
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Both the electric heating rate
and the VPP rate will result in a much lower bill
I know my parents switched and where 14cents last month
I'm not sure which one they took ( depends on what CL&P considers geo , solor or electric )
your KWH was only about 7 higher per day then my parents
the fact your hot water generator was off was likely countered by the high pressure conditions it was under for 2 weeks
I'll be there in 30 min if your worried ,but another month with out those varibles and a discounted rate might do the trick
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thevinmanfxst
New Member
Posts:36
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| 01 Jan 2009 11:50 PM |
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geo fan Am I looking at the correct rates on the CL&P site? Because if so; the TOD (Rate 7) off-peak rate sums up to about $.1647 kWh the VPP on-peak would be $.1706 kWh. the the electric (Rate) 5 is $.1711 kWh. My current regular (Rate) 1 is approx $.1765 kWh. (I left out the flat "Customer Charge" fees to keep everything comparable to usage by kWh.) I can't see where it would ever add up to $.14 kWh Does this sound right??? If so, I'm not sure its gonna be that much savings...maybe $10-$15 a month? All the rates are hereSpreadsheet I used here...I must be misunderstanding something. |
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geo fan
Basic Member
Posts:408
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| 02 Jan 2009 07:02 AM |
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I dont have a hard fast answer for you other then to call cland p
the bill was read to me over the phone so it may be my error
Im not sure if VPP and rate 7 Time of day are one and the same
I just added up the off peak on rate 7 to .15926 not from the vpp link but from the time of day link
thats 8pm to 12am
considering both my parents still work and do everything but thow the main when there not there this could be there plan
or I was wrong still worth a call to the company though ,or not just trying to help |
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thaas53
New Member
Posts:11
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| 02 Jan 2009 10:51 AM |
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I see the VPP peak rate from the rate 7 pdf to be .13777 so using your spreadsheet that makes these the rates:
| on peak |
$0.199830 |
| off peak |
$0.164760 |
I cannot locate the peak rate of .108560 you reference in your spreadsheet for peak pricing. |
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thevinmanfxst
New Member
Posts:36
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| 02 Jan 2009 01:03 PM |
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The TOD (Time Of Day) Rate 7 has off peak and on peak. Your rates come out to be the same as mine: on peak $0.199830 off peak $0.164760 But I think the VPP rate replaces the fixed on-peak rate with a variable one: Here which is .108560 |
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thaas53
New Member
Posts:11
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| 02 Jan 2009 01:40 PM |
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Ah, now I see. That is currently cheaper than the fixed Rate 1 rate. Obviously this rate goes up when demand increases.
Not much difference in their prices of on-peak and off-peak. Wish we had the rates my parents do in Indiana, .015 off peak and .144 on.
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geo fan
Basic Member
Posts:408
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| 03 Jan 2009 07:27 PM |
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My apologies , on the bad numbers after speaking again to my family ( father this time ) they are on the vpp rate and your numbers where accurate on peak accounted for roughly 25% of there bill
It would be fair to say that you would have spent 1750 this year on oil ( during the winter ) based on local prices at 2.51
This year during the same period and based on your first bill if you where over 700 I would be surprised
Say for the intire rest of the year it costs you 200 for priority hot water ( complete guess )
you would replace a 2525 bill with 900 ( keep in mind Im using today's oil prices )
I know Im not telling you anything you dont know , And I dont want to hope for high oil prices to make this point more compelling
I just wanted to let you know that even with the dip in oil and our high electric rates your still doing great
also look into collective energy Im not sure how it works but Im looking into it now
They appear to be a coop of some sort 10.49cent generation charge locked in for a year still use cl and p for transmission
Its though con edison doesnt look like a scam slightly lower then off peak 24/7 |
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geo fan
Basic Member
Posts:408
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| 03 Jan 2009 09:16 PM |
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And you have Public Power and Utility out of New Milford
they offer 11.2 cent rate and in there fine print states there rate will fluctuate but will never rise above 5% less then CL and P
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thevinmanfxst
New Member
Posts:36
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| 03 Jan 2009 11:51 PM |
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Good call. I already singed up for the PP&U generation
service a few weeks ago. Just waiting for them to switch me over. But according
to my calculations, I would have saved $15.48 on last month's bill. (That's
.005 cents per kWh cheaper...nothing to write home about, but its something.)
In fact, if you read carefully, I think all PP & U is doing is not having
to charge the FMCC tariff (which is .0055 kWh)...it evens says in the CL&P
Rate 1 document the FMCC tariff is "Not Applicable for customers paying
for Third Party Service." or maybe its just a coincidence....
Maybe they will turn out to be much less in the future, but I'm not holding my
breath. But thanks for taking a look at the alternative generation
services for me! Speaking of co-ops, I know there is an oil co-op
that's delivering $1.89 oil last week to my town...($25 a year
membership) - Citizens Oil Co-Op.
I also hope your $900 is correct...interestingly enough, I have a paper from
the manufacturer here (pink one, you may have the same) that states for a
Northeastern located, 3k sq ft house, same 5 ton unit, @ .10 KwH, operating
costs for heat would be $992, Hot Water $125 & Cooling $149) - Do that math
and that's 12660 kWh, and bump that up to .18 kWh, that's a grand total
operating cost of $2278. (I also expected that to be conservative, since
its a sales document.)
Ouch...
Anyways, before freaking out, I just want to understand if my
observed/estimated 1427 Kwh/mo was
reasonable for a comparable system/house/region, or if there may be leaks
somewhere, system is sucking wind, or maybe a gremlin in the compressor, etc.
Next months bill will probably be a whopper and I'll run the numbers again,
against oil and kWh used last year...maybe the picture will become clearer.
Thanks again all!!!
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geo fan
Basic Member
Posts:408
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| 04 Jan 2009 12:53 AM |
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Yeah my crude estimation so you know is based on Dec , Jan =2/3 Oct+Feb=1/3 very scientific |
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thevinmanfxst
New Member
Posts:36
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| 16 Jan 2009 10:33 PM |
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- Update -
Just got my electric bill today...here is the damage:
Last year - On Oil, for December, I used approx 117 gallons.
This year - On Geo, for December, the Geo used approx 1649 kWh.
If 117 gallons (@85% eff) = 13,823,550 BTUs and
If 1649 Kw (@100% eff) = 5,628,037 BTUs
Then my COP is looking like 2.46 (according to the "tests" that were run...and the docs from my installers it should be closer to 4.3)
What the heck?! Is my math wrong or is my system in need of some "examination"... |
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cnygeo
Basic Member
Posts:170
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| 17 Jan 2009 09:49 AM |
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Your math is sound. It's a pretty crude method, but if anything you're probably oversetimating COP slightly since very few oil systems actually achieve an average efficiency of 85%.
I was going to say that you need to account for different average temperatures during the two periods, but it looks like the average temp for Dec 2007 was very close to Dec 2008.
In your previous posts you indicated that you were estimating your heat pump kWh by taking the difference between previous and current year bills - is this still how you're doing it? If so, that's a huge potential source of error. Also, if you're getting the numbers from an electric bill, make sure the period of time is the same and that the meter reading is actual and not estimated. My electric co seems to let my billing period drift by several days in either direction so I could have 35 days on one bill and 25 on the next.
The estimate for annual electricity use you posted seems pretty reasonable to me. A VERY crude estimate when replacing an average oil heating system (85%) with an average geo system (COP of 3.5) is to expect to use 10X you annual gallons of oil in kWh. In other words if you used 1000 gallons your heat pump would use about 10,000kWh. Again this varies hugely depending on the COP of the heat pump etc but it gives you a ballpark idea.
When did they commission your system? There's a good chance the ground temp was near it's highest temp at that point so the measured 4.3 would be a best-case COP for the season. We would expect it to drop significantly as the ground gets colder and more heat is extracted from it. Can you measure the temp of the incoming refrigerant line from your loop field? |
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geo fan
Basic Member
Posts:408
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| 17 Jan 2009 11:15 PM |
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just wondering where did the 117 come from ? seems low based on your other statements , specificly the 700 between dec. and march even divided equaly ( unrealistic considering the temps in dec, jan ) would give you around 175 ?
Im not questioning your calcs , just wondering where the number came from |
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cnygeo
Basic Member
Posts:170
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| 17 Jan 2009 11:36 PM |
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Good point, I missed that. If he burned about 1000 gallons for the year, 117 seems way too low for December. If it was really 700 from Dec 1 thru Mar 31, I'd expect about 185-190 gallons in December based on the temperatures 2007-2008. Assuming his kWh are correct that would give a COP of 3.8 or so. That's like buying oil at $1.63 a gallon assuming $.18/kWh. |
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