Hi everyone! I have a general question that I cannot seem to find an answer to in my online searching/researching about geothermal. But first, a bit of background info: I am in central Massachusetts, and am building a new house (so I cannot compare this system to an old systems' usage) so I am very nervous about the whole thing. After reading several posts here, something has come up that I had not yet thought of; electric usage. So, with a system that will be a closed loop verticle, servicing a house for heat, AC, and HW, with about 5000+sf of living space, is there a way to "plan" the electrical usage and project that number? I have NO IDEA how much the system will need to run, but from what I read, it seems like it runs longer and therefore uses more electricity. Correct? I think I need to determine that number to help me calculate the overall costs and ROI. Any help and/or advice is EXTREMELY appreciated. thom

Nevermind. I found some info ina post of about $300/ton/year. I will use that as a guesstimate. Sorry I cannot delete the post.

is there a way to "plan" the electrical usage and project that number?

Yes. It starts with a study of the location and home you are building to determine what your heating needs will be. Once you know how much heat you are expected to use, you can get an analysis of your various options. For example, a geothermal system might cost more to begin with, but it might save you money on your heating bills each month. A gas furnace might be very inexpensive to install, but it might cost more in the long run.

The study of your new house (walls, roof, foundation, insulation, climate, etc.) is called a "heat load determination" or sometimes, a "Manual J" and should be done by an independent entity you can trust. HVAC companies will often offer to do them for you for free, which is very attractive, but I have seen too many that are skewed in order to sell you something that maximizes the HVAC contractors profits and not your best interests. Once you have your heating and energy usage projections, you can go out and solicit bids for systems that will be matched to your heating needs and lifestyle.

If your heat load was done competently, you should be able to project fairly accurately what your energy usage (and cost) with the various systems will be, assuming the weather cooperates.

Posted By ICFHybrid on 02 Feb 2012 06:53 PM

is there a way to "plan" the electrical usage and project that number?

Yes. It starts with a study of the location and home you are building to determine what your heating needs will be. Once you know how much heat you are expected to use, you can get an analysis of your various options. For example, a geothermal system might cost more to begin with, but it might save you money on your heating bills each month. A gas furnace might be very inexpensive to install, but it might cost more in the long run.

The study of your new house (walls, roof, foundation, insulation, climate, etc.) is called a "heat load determination" or sometimes, a "Manual J" and should be done by an independent entity you can trust. HVAC companies will often offer to do them for you for free, which is very attractive, but I have seen too many that are skewed in order to sell you something that maximizes the HVAC contractors profits and not your best interests. Once you have your heating and energy usage projections, you can go out and solicit bids for systems that will be matched to your heating needs and lifestyle.

If your heat load was done competently, you should be able to project fairly accurately what your energy usage (and cost) with the various systems will be, assuming the weather cooperates.

OK, but is it possible to get the manual J prior to construction? Can it be based off of the house plans/blueprints? Obviously I cannot build a shell of a home and tell the builder to wait on a heating system. I should have warned you all that I am kind of dumb to this whole thing. Sorry. So if I can get the Manual J done, and then I get bids, they should be able to tell me the projected "usage" of the system...which will allow me to project the numbers of the operating costs so I can determine my ROI. I know that the builder was planning on $22+K for an HVAC system, so I am responsible for the difference in the price.

Can it be based off of the house plans/blueprints?

Yes.

At some point, the person doing the Manual J will make an assumption about the "tightness" of the house in order to calculate air infiltration. If you want it to be accurate, someone will have to make sure that the house is actually built to that air tightness. Of course, this applies to all the assumptions made, including the quality of the doors and windows as well as the construction method and insulation planned, it's just that builders don't seem to have as much experience with the air sealing standard, yet.

Posted By ICFHybrid on 02 Feb 2012 07:36 PM

Can it be based off of the house plans/blueprints?

Yes.

At some point, the person doing the Manual J will make an assumption about the "tightness" of the house in order to calculate air infiltration. If you want it to be accurate, someone will have to make sure that the house is actually built to that air tightness. Of course, this applies to all the assumptions made, including the quality of the doors and windows as well as the construction method and insulation planned, it's just that builders don't seem to have as much experience with the air sealing standard, yet.

AWESOME!! Thank you very much!

Once you have a solid Man J off the plans it is possible to ballpark the total heating or cooling needed for an average season using "equivalent full load operating hours" or hourly bin data.

From manufacturer extended specification tables and your particular loop deisgn parameters you can determine power required to operate your system for an hour and proceed from there.

Another approach is to determine the number of btus the structure will require throughout a heating or cooling season and calculate the cost per million btus of various methods of heating and cooling.

The $300/ton/year is what we see at 14 cents per kilowatt hour. That is for heating, cooling, and DHW. That assumes that the tonnage is correct for the house.

Doc, Thanks! According to my current bill, we are paying $.08. Hopefully by the time we are done building they will still be charging that little!

That is an interesting way to describe cost of operation. Factoring in our somewhat cheaper power ($0.12), that probably holds true down here at $250/ton/year. I have what is effectively a 2 ton system, and it costs about $400 - $500 per year and makes most of the hot water as well.

It would be interesting to present to customers annual cost per ton for alternative systems, since down here almost every home has a heat pump