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Heating & Air Conditioning

Propane tank size for house with geothermal

8 years ago

Wondering if anyone here can help me with this - I am in the finishing stages of a new build home in the NE. We have chosen to do geothermal for heating and cooling. We are also planning to have a propane tank in the ground, as we will be using propane for the stoves and fireplace. The house has an in-law apartment attached, so there will be 2 gas stoves and one gas fireplace. We were planning to use a 500gal propane tank, but the builder is advising us to size up to 1000gal. We have had some concerns about the builder's motives in general, so I was hoping to ask for advice here. Would we need that big of a propane tank? Difference in cost is $700. Thanks in advance!

Featured Answer

dekeoboe

8 years ago

last modified: 8 years ago

We have Geothermal and use propane for the stove and the outdoor grill. We have a 250 gal tank and seldom get it filled. And we do not eat out. I can't see why you would need a 1000 gal tank unless you are planning on installing a generator.

EDIT: Our tank is 120 gal tank and we go over a year between refills.

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Comments (8)

fsq4cw
8 years ago
I would consider the $700 upgrade to the 1000-gal tank and
possibly install a high efficiency gas furnace for the geothermal backup along
with a ‘Split’ geothermal heat pump. You can shop gas prices and fill up less
often at a lower price with less of a chance of running out of fuel. You could
also install a propane generator if there are frequent electricity outages.

IMO

SR
Elmer J Fudd
8 years ago
Choose a propane company now and ask their advice - they're a better source of good information than your builder
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The info you provided isn't enough to size the propane tank. You also need to consider the scenario and what applainces will be running at the same time and for how long. The big drivers will be the heating system, freplace, generator and hot water. Find out the gallons per hour ratings for each of these and multiply by the number of days you need. Keep in mind that the propane tank is only filled to 80% of maximum capacity to allow for expansion, so a 500 gallong tank will only have 400 maximum gallons; 1000 gallon tank has 800 gallons. Also- you need to figure that when an outage occurs you probably won't have a full tank. I looked at the Kohler 15kW specs and it is rated for about 1.5 gallons per hour of propane usage at a 50% load (idle speed). A 2 week outage would use over 500 gallons assuming you ran the generator continuosly for that entire time. So that alone would put you in the 1000 gallon tank class. But I would really think hard about this 2 week requirement. If that is what you really want - then you probably would need a generator that is liquid cooled and not air cooled (air cooled are cheaper). The liquid cooled gensets may consume more fuel - check the specs. 2 weeks of continuous operation is a long time on a genset. I worked out the tank capacity with the propane service provider. They not only sized the tank, but they also provided a special valve to ensure that the pressure was regulated when the genset is running. The tank size won't change the gas pressure coming into the house since it the regulator keeps the right pressure. I would also look at the genset size. Since your hvac is gas, you don't need a lot of power to keep the house comfortable and rive all of you appliances and well pump. A smaller generator will use less fuel and will be cheaper to install. I have a 12kW Kohler unit and it is more than enough to run the house during an outage. We live in VA and have had some long outages - over 24 hours with no power with near zero degree temps is a long outage. The 12kW works like a champ. Also - make sure you get BOTH the carburetor AND batttery warmer heater accessories for your genset. These are a must in cold weather and will make sure the unit starts in very cold weather.
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Buy it. If you rent it, you can't price shop and will pay higher prices for your propane. You may also pay an additional premium as a captive customer, since you won't be able to predict your usage very well. They should be able to run off of one tank. For backup, I would buy a 500 gallon tank. By law, they can only be filled to 80% of capacity, so a 500 gallon tank only holds 400 gallons of propane.
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I hope the person takes my previous advice. The regulator is not the only limiting factor. The surface area of the gas in the tank is a limiting factor. The gas must "boil off" and become vapor prior to leaving the tank. A small surface area delivers less vapor than does a large area. Cooler temperatures also slow the transition from liquid to gas. So the propane vaporizes more slowly at the very times that demand is greatest. Propane dealers can determine the tank size needed for your application.
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Comments (4)
We have a 500 gal underground tank used for cooking, dryer, and gas fireplace. A fill-up typically lasts us 2-3 years. It depends upon fireplace use more than anything else for us. In the colder months we'll use it for 3-5 hours a day every day. That amount of use for about 4 months typically uses about 1/3 of the tank. When we had it connected to the pool heater, we used a tank per year. Our main heat source is geothermal with electric backup. I don't know how the water heater would impact use of propane. My guess is that you might use 1/2-3/4 of a 500 gallon tank/year. I think the 1000 gallon tank is probably overkill. You can do a partial fill in the summer if you want to take advantage of lower prices and the tank isn't empty.
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dreamhouseforsomeday
8 years ago
We too plan on having propane for stove & oven. Look around the appliance forum for information on "propane ranges" or something similar. You will find posts about how much propane people typically use for cooking and how often they have to refill their propane tanks. Also, check the recommended specs on distance(s) from the house for different tank sizes--I'm not an expert (so please no one bash me on this...it's just my guess) but I think it has to do with safety. The larger the tank, the further from the house it should be. Search "propane tank distance requirements".
irina654
Original Author
8 years ago
Yes, dekeobe - that's exactly the conclusion we came to. We wound up going with the 500gal tank - both the propane company and geothermal company agreed that unless we are powering the house from a generator for an extended period of time, we would not need a larger tank.
jrb451
8 years ago
Did they estimate the # of hours a 500 gallon tank would run a whole house generator? What's a 500 gallon tank run, if you don't mind me asking?
irina654
Original Author
8 years ago
We were told the 500gal tank would allow us to run a generator for 5-7 days. We don't have the price for the 500gal tank - we are building a house with a builder who doesn't tell us what anything actually costs, just what the difference is from the base price (which is usually 2-3x the amount if we are upgrading and 1/2 -1/3 of the actual amount if we are downgrading). In this case, we are getting a $700 credit for downgrading from the 1000gal to 500gal tank.
Elmer J Fudd
8 years ago
last modified: 8 years ago
"we are building a house with a builder who doesn't tell us what anything actually costs, just what the difference is from the base price"

That will only continue to be the case if you let him continue to get away with BS like that. Your relationship is whatever you demand it to be in this regard, you're the customer and presumably paying him a lot of money. That should buy his attention to your reasonable requests.

Sorry, I'm not trying to agitate you, but another question comes to mind. If he over-spec'd (and over-charged) for what was needed for a propane tank, what else is in the bid that he did the same thing with? Hopefully little else.

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