So I just purchased a new home. Heat and hot water are all oil. Current owner advises that he used 730 gallons of oil over 12 month period. In an ideal world does this analysis seem about right? 730 Gallons * 138,700 BTU/gal * 80% efficiency = 81,000 MBTU at 3413 KWH per BTU, I need a total of around 24,000 KWH of heat. If I assume I can meet 80% of my heat and DHW load with Geothermal at COP of 4.0 and the other 20% resistive heat at COP of 1.0 So my load is 19,200 at COP 4.0 and 4,800 at COP of 1.0 or 4,800+4,800 for a total of 9,600 kWh purchased from the utility for heat. So my comparison is 730 gallons at $4 for $2920 per annum versus 9,600 kWh at $0.09 for $864. DOes this seem like reasonable assumptions for a mild climate (MD) with higher water use (family of 6) I realize I am looking at heat side only. I'd expect to realize some savings on AC as well.

Great job with your math there, I would say that is a very fair assesment of things. The biggest thing is your oil furnace really operating at 80% efficient and most Geothermal systems we put in get a bit over 4 COP in real world conditions when we do come back and check EWT/LWT performance.

Don't forget that you may use more or less oil than the previous owner and that each winter is colder or warmer than the last but those are great estimation numbers to use.

I also have a family of 6, and while being in Massachusetts means I have a better chance of a worse winter than you do, I agree with Sky in regards to being careful what other people use. The house size (and room sizes & heights) will determine how much oil YOU will use. Do you like it warm, hot, cool? Do you all put on sweaters, or run around in t-shirts? I only say this because my wife is ALWAYS cold, and the kids are in t-shirts like it's Springtime. I leave my thermostat at 67. I was using closer to 1100 gallons a year for a house built in 2001, that was 2800sf. No overly large rooms, and ceilings all 8 foot high.

I also sold Real Estate for almost 10 years, and found that owners will say anything, and reveal little. Even if you got our hands on copies of the bills, they would only reflect that owners preferences. I always loved it when Buyer would ask to see the electric bills for the year. I always laughed and asked if they intended to have the exact same lights on for the exact same duration, and how they would know! My point is be careful with your assumptions of usage, as it may vary widely. Either way you slice it, Geo is a great way to go!

Sky, The current boiler is fairly new. EnergyKinetics system 200 that I think is rated at 85% or so, so 80 was my best assumption.

TL, I did not ask current owner for utility bills until a few weeks after we had the contract signed, so I don't think he's holding back. I presently have everyone in my current house in long sleeves and flannel PJ's and one of the reasons I want to go with geo is so I can stop abusing my family and making us all run around the house like mummy's.

Posted By mtrentw on 08 Mar 2012 03:01 PM
Sky, The current boiler is fairly new. EnergyKinetics system 200 that I think is rated at 85% or so, so 80 was my best assumption.

TL, I did not ask current owner for utility bills until a few weeks after we had the contract signed, so I don't think he's holding back. I presently have everyone in my current house in long sleeves and flannel PJ's and one of the reasons I want to go with geo is so I can stop abusing my family and making us all run around the house like mummy's.

Big smile on my face while reading that! My kids are NUTS, as I am always in fleece tops and rubbing my hands together! I cannot wait for my new house to be finished! Good luck with yours!

Matched with the BIN data for Andrews AFB, you are also looking at about 40.000 btus/h heatloss with an 85% furnace and 10F design temp (98%). A 3 ton system would use 4% aux heat while a 3 ton system would use 1% aux heat. You have to be careful, 710 gallons and a 85% furnace, your heatloss actually goes up compared to an 80% furnace, given the same gallons used, since more heat goes into the house and not the chimney. It is dangerous to rely on other person's consumption data. Many times I hear later that they also burn 3 cords of wood in the fireplace, after you probe them for it. Or they simply lie. Or you run the thermostat differently. So be careful here and have a manual J done as well.

The heatcalc spreadsheet from EIA does a great painless job of comparing various heat systems. You can plug in your local fuel costs and efficiency info and it does the calculations:

http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&cts=1331257334010&ved=0CCkQFjAB&url=http%3A%2F%2Fwww.eia.gov%2Fneic%2Fexperts%2Fheatcalc.xls&ei=8l9ZT7fpAur30gH4wei_Dw&usg=AFQjCNEI3O4-27x7XDhiFFJKOpjvhEZHsA

Definitely get a heat loss done on the house if you really want an accurate #. Any free energy audits complete with blower door test in your area?

What made my decision to switch to geothermal was when I went to order fuel oil, it was going to be almost $1,000.00 for a tank that would last no longer than 6 weeks. I ran the numbers and my installer ran the numbers, they came out really close to one another. Now my house is 71 degrees, the three year old is wearing a swim suit running around and the wife's feet are warm. Before the house would barely stay 71 and the furnace ran all the time. Since the additional ducts and cold air returns were installed it stays 71 all the time.

I am going on my third week of running off my geothermal and I read the meter every day, I will post my numbers after I gather some more data.

Switching from oil to geo is the easiest, as your math bore out.  I am glad that "lifestyle choices" in regard to the thermostat came out.  As the price of oil went higher people misered to cut cost.  The amount of oil needed to satisfy your comfort could be more or less.

For a family of six, the female count would drive my choice on domestic hot water.  I am an advocate of a stand alone on demand heater like the Rinai, or even feed it with geo if the extra plumbing and buffer tank make sense to you.
Eric

One driver in getting rid of oil is to remove the liability of a 30 year old underground tank. NG is not an option and I don't want to trade oil for gas, so I do not think tankless is an option. I have 3 females now and an unknown on the way. Seems the laundry is running every day, so I expect water use to remain high.

Since the current oil setup is an indirect hot water heater with 80 gallon unpowered DHW storage tank, I am planning to simply re-use the buffer for DSH and add in a finishing tank. Based on the house set-up (current is a 3.5 ton heat pump for main house and 1.5 ton for in-law apartment) I am fairly certain I will be forced into using 2 units. I don't close and move-in until May 1st, but my best guess at present is to get a 3 Ton package unit in main house and add a 2 Ton split unit (by the way does anyone know if there are manufacturers at a 1.5 Ton size in a split unit) for the apartment. This way I can keep the units co-located and use a DSH on both. With the significant differences between main house and apartment, I expect very different run profiles from the units, so it should spread my water production out.

At any rate, I've got a list of 5 contractors who install geo in the area. I plan to have at least 3 out to see the different options they come up with to skin this cat.

WaterPirate, you may be able to offer some guidance based on your area of operations. If you travel due west from Dagsboro and cross the Chesapeake, I am in Owings, MD. The house is 30' above sea level and I am 300 yards from the Patuxent River. I would guess that the geology might be similar in this are of southern MD as you would experieince on the Eastern shore. I am wondering: 1. Do you know if pump and dump is allowed anywhere in MD. I have a steep drop into a creek just 15 feet from the side of the house. 2. If so, how variable are water tables and water quality. I am thinking between say Choptank, Easton, Galesville creeks and tributaries. Do you (generally) find similar conditions along these creeks?

Hi and welcome,
MD is a wierd duck. Every county has different rules for just about everything. Yes the lithology is similar but you can encounter some obstacles on the western side of the bay that do not present on the eastern shore. I would call Buddy Winslow well and pump from down near hollywood to get your specific questions addressed. They do commercial as well as residential loops and wells.
Eric

mtrentw I am also in Owings and have a very similar Home on Chaneyville Rd. I would love to show you my 3 Ton Climatemaster system and show you my numbers and photo's of the install if wanted. Send me a email at [email protected] if interested. Thanks Paul Wagner