LP Questions

mydreamhomeJune 10, 2012

I hope this is the right forum to post this question. Our HVAC guys were the ones to handle the LP gas lines and install of the rangetop & tankless hot water heater that run on LP. My question is, how much LP should we be going through on a monthly or yearly basis? Here are the details:

-We've been in the house since Oct.

-The tank is a 500 gallon one that they only fill to 400.

-We use the rangetop 5-6 nights per week (max 18K BTU on all burners), utilizing typically 1-3 burners a night for less than 30 minutes each.

- 1-2 showers per day for family of 4.

-We fill the 5.5' long whirlpool tub maybe 1-2 times per week.

-Laundry usually done on weekends--around 6 loads per week.

-Based on the tank fill amounts, we have been using about 100-125 gallons of LP per month.

That comes to about 3 times the amount my parents use. The biggest difference between our household and theirs would be the laundry (2-3 loads per week for them vs. 6 for us) and the showers (we both use our tubs about the same amount and theirs is actually bigger.)

Does this usage sound about right? Or should I be worried? I asked about having the system checked for a leak, and was told that if they tested and there was no leak, then I would owe them around $300 for the test.

Thanks for any insight anyone can give.

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You said you have a family of four and your parents are a family of two, correct? Twice as many people equal twice the energy usage.

    Bookmark   June 11, 2012 at 8:56AM
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Are they using a whirlpool tub as well?

Are you not using gas for heating?

    Bookmark   June 11, 2012 at 3:38PM
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Thanks for the responses. In reply & to answer the questions...

-Twice as many people should = twice the usage, I agree, but we're at 3 times the usage. That's why I'm asking the question. It seems high to me, but we've never had gas before much less LP. Mom & Dad fill 2x a year and it looks like we'll be filling 6x a year.

-Yes, they also have a whirlpool tub--ours is shorter than theirs, but deeper, so its pretty much a wash in terms of amount of water heated. We use them about the same amount of the time.

-We have some kind of hybrid heat pump that switches over to gas from electric when the outside temperature is cold enough to activate the heating strips. We had a very mild winter this year and it never got cold enough to activate the strips. Our LP usage has been pretty much the same each time the LP company comes to check on us and refill--3 times Oct thru April. I'm expecting them to be back again in the next couple weeks & the meter is down to 40%.

Thanks again for any help!

    Bookmark   June 11, 2012 at 8:30PM
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Does your heatpump run most of the time or your LP gas furnace? Your heatpump should be running the vast majority of the time, if not that explains the increase in your usage.

    Bookmark   June 12, 2012 at 12:33PM
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neohioheatpump--as far as I know, we don't have a gas furnace per se. It's all 1 unit with the heatpump system switching to LP only when the heat strips turn on due to sustained extreme cold. Other than that, it should be running on electricity. Are you suggesting that perhaps its running on LP all the time as opposed to electric and only using LP on an as needed basis?

    Bookmark   June 12, 2012 at 8:53PM
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Yes. Kind of.

You have a 'dual fuel' system. I would like to say that this comes with an outdoor temperature sensor which is connected to the thermostat. Then the thermostat is set up so that gas is allowed to be used below a certain temperature. There is also a setting where the HP only operates above a certain temperature. These settings can allow both gas and HP operation at the same time (which is not a bad thing).

It could be that for your unit, the temperatures are set too high and you're using more gas than you should.

As an example, a decent 15SEER HP may produce good heat down to 28F. But you might feel that the air it produces isn't warm enough so you set the gas activation point to be 35F. So anytime the temp is between 28F and 35F both HP and gas might activate at the same time (HP first, then gas). Below 28F only gas would be used. Above 35F only HP.

Yours may be set higher, like 40F or 45F.

    Bookmark   June 13, 2012 at 4:05PM
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Thank you so much, weedmeister! That is a great explanation. I will definitely look into that and see if it is indeed the problem. And now that you explained it, it makes me think about my electric bill. The house we built is twice the size of our old house (we built both new), and the electric bill is pretty much the same--less than $10 difference per month. I chalked it up to not using an electric cooktop & hot water heater, but maybe the HP is skewing the numbers there too.

Thanks again!

    Bookmark   June 14, 2012 at 12:26AM
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"These settings can allow both gas and HP operation at the same time (which is not a bad thing)."

Is this correct? They can operate simultaneously?

I have an oil furnace plus a HP. They can not operate simultaneously.


    Bookmark   June 14, 2012 at 12:38PM
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100 gallons a month is a lot - no question.

Cooking is a joke. We have an outdoor grill and a 48 inch range and we cook a lot. NG bill is either $.80 or $1.60 per month (1 or 2 therms which is not terribly different than 1 or 2 gallons.)

Hot water should be about 20 therms with a tankless for NG.

You should have solar hot water. LP is no way to heat water in today's day and age. If you have reasonable electric, a heat pump hot water heater will save you tons.

    Bookmark   June 14, 2012 at 1:46PM
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S: Yes, as far as I know. The Gas would activate as Auxiliary Heat if the HP could not 'keep up' or meet the demand in the overlapping range.

    Bookmark   June 14, 2012 at 3:29PM
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Hi David_Cary! Don't know if you remember, but I'm just a couple counties over from you in Randolph. It's nice to know I'm not crazy for thinking that was alot of LP usage. It would have cost us $12K (yes you read that right) to run the NG line to the house from the street, so NG wasn't a viable option. The solar option sounds nice, but we didn't think it was feasible based on the house setup on the property. The tankless hot water unit was the compromise, that way we're only heating the water we need when we need it--which is typically in the mornings & evenings between 6 & 730. How much do you cook with your 48" rangetop & how many burners going at once for how long? How many people in your household? I'm guessing your hot water heater runs off solar? Anything else in your house use NG?

    Bookmark   June 14, 2012 at 9:58PM
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We have 3 people and cook 5 nights a week. Mostly from scratch - decent amount of wok usage. Honestly the grill probably uses more since I usually turn it on for 10 minutes just to clean it prior to cooking. I don't go around doing the corn in a husk for 30 minutes though. We don't can or anything particularly intensive. And the ovens are electric. But even if you used 3 times what we did, you are around 5 gallons. I would think 10kbtu for 30 minutes is an average meal. That gets you about 1 therm a month with 20 meals. Sure we cook breakfast too but that isn't much. Not a lot of cooking on the burners for lunch.

We have fireplaces and a dual fuel heating system. I changed the switchover to 40 degrees this year since NG fell in price but I still only managed to use 70 therms this winter for 5000 sqft. But 150 per winter is a more average usage - total season not monthly.

Our hot water is solar.

Since you have dual fuel, you really need to look at your switchover. Since LP is so expensive, it should be set in the mid 20s. Then cut the furnace out at 35 or so. LP should almost never be used with our electric rates.

Too bad you were talked out of solar. It is hard to build a house that can't do solar. If the trees are that close and tall to the house, they usually come out or die from root damage. You don't need much sun in the end. I guess if it is a ranch, then it is possible.

    Bookmark   June 15, 2012 at 7:55AM
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