Geothermal

[muncybob]

Many people in this area are installing geothermal units of one type or another. Many of the contractors I've spoken to about possibly installing a wood boiler are busy installing these systems. I was under the impression that they only worked with hot air systems but I've read that there are systems that can be combined with baseboard heating systems. I know the upfront cost is up there(but even a good gasifier wood boiler with storage isn't cheap these days!) .

My question is how can I determine the apprx. cost of running a geothermal system to heat my house with today's electric costs? With wood I can approximate my wood usage based on my heat loss and determine my cost of heating on that but am unsure how to look at the geothermal costs after installation.

I know with deregulation, the cost of electricity will increase(and depending on who you talk to it will be a moderate or even extreme increase) but geothermal does interest me.

 

[Redox]

"Geothermal" is a bit of a misnomer for a ground source heat pump (GSHP). Basically, it is a heat pump that has a water to refrigerant heat exchanger instead of an air to refrigerant heat exchanger. They are more efficient because the earth's temperature is about 55F year round. They also don't have to defrost in the winter.

That being said, they are still a heat pump with all the drawbacks of a low temperature heat source. There are apparently water to water heat pumps available, but they will only work if you have radiant heat or something that can work with 120F water. The highest temperature you will be able to get off a compressor is about 120F and this won't do squat with conventional baseboard. It also won't give you A/C, either. If you are going to do it, a good duct system will be necessary as well as a very tight house. The duct system will be the least of your problems if you don't have a well insulated house.

The operating cost is supposed to be the lowest of any type of heat ('cept for free wood!) and should remain so for a good while; certainly lower than oil and propane. The equipment cost (excluding the well or ground loop) is excessive in my opinion because there are few manufacturers out there. The basic machine isn't any more complicated than a regular heat pump, but they command 3-4 times the price per ton for a GSHP and you still have to drill a well or lay a lot of pipe in the ground. The technology is mature, but experienced contractors are spread pretty thin.

Chris

 

[Jerry_NJ]

I've been happy with my forced air Geothermal. It is about 15 years old and has not required any service other than changing the air filters over this time. My in a Waterfurnace brand and has a coefficient of performance for heating in low speed of approximately 4 (1/4th the cost of heating with resistive electric). This is rather low temperature, gives about a 20 degree rise over the room temperature when measured at the top of the heat exchanger. It delivers and EER of about 20 in air conditioning. From this you can figure heating costs just as you can for wood heating.

I run a 100% electric 2,000 sf two story house with two adults for about $2,200 per year at the current (higher) electric rates of 20 cents per KWH in the summer, I expect to see that drop to something near 17 cents per KWH in the winter, now. This is for everything for energy, no gas/propane or oil bills.

 

[d.n.f.]

My neighbour has a backhoe and put his lines in himself. However I seriously doubt he is going to put in the unit. They are very very expensive. I have heard payback time is pretty good but you better not be moving for at least ten to fifteen years.

 

[joephu]

To answer your question about cost, you need to calculate the BTUs per unit for each fuel type, then factor in the cost per unit and the efficiency rating. For example:

Let's assume electricity is $0.17 per kWh; wood is $175 per cord; and oil is $4/gal. The BTUs per unit is 3413 for electric, 20,000,000 for a cord of wood, and 138,690 per gallon of heating oil. As for efficiency, let's assume geothermal is 400%, wood is 65%, and the oil furnace is 80%. Here's how is bears out:

1. Geothermal: (1000000/3413 BTUs) x $0.17 is $49.81 per MBTUs. Then divide by 400% efficiency = $12.45 per actual MBTU. This is 803 BTUs per $1 spent.
2. Wood Stove: (1000000/20,000,000 BTUs) x $175 is $8.75 per MBTUs. Then divide by 65% efficiency = $13.46 per actual MBTU. This is 743 BTUs per $1 spent.
3. Oil Furnace: (1000000/138,690 BTUs) x $4 is $28.84 per MBTUs. Then divide by 80% efficiency = $36.05 per actual MBTU. This is 277 BTUs per $1 spent.

At these assumed rates and efficiencies, geothermal is:

190% more efficient than heating oil
8% more efficient than wood

Obviously, if the cost per unit and/or the efficiency of your heating source is different, than this would change everything. Hope this helps somewhat. IF you want the spreadsheet I created, just send me a message.

 

[muncybob]

Joe..thanks. Now I have my mind "around" it! Spreadsheets are my life, but thanks for the offer! I'll now play with some numbers just out of curiosity...but the big unknown here is just what will the rate of electricity be after deregulation! I need to fix my crystal ball!

 

[Jerry_NJ]

Good on doing the numbers, joephu.

I'd say the costs are about right for NJ for electric power, but low for wood, more like $250 per cord and lucky even then to get a full cord, and heating oil is closer to $3 a gallon - I say without personally checking on oil, I don't use it. Now as for efficiency, one may get a cop of 4 with a ghp, but most will average more like 3 to 3.5. My unit ranges between 4 and 3 depending on the "speed", and when it gets cool it spends increasing portions of its run time in high speed... or cop of 3. So, throwing those "spins" I'd say the benefits of ghp and wood over oil are still significant, but not as high as your exercise, at least not in my experience in NJ.

NJ has had "deregulated" electric power for several years, going back to the days of oil sell for a bit over$1 per gallon, and during that time we've seen oil go up 300%, or up to $4 per gallon, while winter rates for electricity have gone up about 70%, from 10 cents to 17 cents per KWH. So, history says as energy goes up, oil goes up faster so far. But, given I've seen gas go down to about $3.10 per gallon from over $4 says oil products also go down in cost, I don't remember ever seeing a reduction in electric rates....other than the winter rates being lower than summer rates.

 

[Redox]

Joe..thanks. Now I have my mind "around" it! Spreadsheets are my life, but thanks for the offer! I'll now play with some numbers just out of curiosity...but the big unknown here is just what will the rate of electricity be after deregulation! I need to fix my crystal ball!

I've found a Ouija board is more accurate! :smirk:

The price around here jumped 72% after deregulation, so this may be a reasonable number to figure on. Wasn't it supposed to get cheaper?!? The numbers on cost/BTU may move around a little, but if you have to pay for wood, the heat pump is going to be competitive. It all really depends on you and whether you want the hassle of a wood fire, or would rather have the simplicity of thermostatically controlled heat.

I'm lucky to have natural gas, but I am using air-air heat pumps to take the chill out in the spring and fall rather than burn something. They generally have a COP around 3 at 47F (rating point) and can help conserve wood until it starts getting cold out. After we get consistently down into the 30s, I will light the stove and keep it going pretty much 24/7 all winter. I save the gas for really cold weather when the stove is a little challenged. If I had to pay for oil, I might just let the house go colder. A conventional air-air heat pump may be a good compromise if you can't quite get your arms around the $10-20K first cost of a GSHP.

I'm just thinking out loud here, but they have been using water source heat pumps in commercial buildings for years. They are basically a self contained water-air heat pump that connects to conventional ductwork and can be had in single phase up to 5 tons. Functionally, they are the exact same thing as a GSHP in a plain brown wrapper without any added bells and whistles. They are typically connected up to a boiler and cooling tower to keep the loop between 55-85F. You might not be able to get one with a desuperheater or two speed compressor, but they are half the cost of what is being marketed to the residential consumer. If I were trying to do something on the cheap, I would befriend someone in the commercial business and see what they can do. If you really wanted a two speed, you can put it on a VFD and make it variable speed and still probably spend less than what some of the Gucci brands cost. The big three all make them and there IS some competition there.

Chris