one or 2 tank setup? Please start a new thread, I will be happy to explain.

one tank setup

Ok -

I'm back with my most recent electricity bill. For the time period between 1/07/11 and 02/05/11 I used 1015 kWh for a total charge of $158.39 i(incuding cost per kWH, delivery charges, taxes, fees, etc.). Simple math would tell me I am paying $0.156 per kWh. FWIW, my average monthly usage is about 800 kWh over the past 12 months.

That's a high enough rate that this isn't a slam dunk.
Need your heat loss calcs.
j

I downloaded the trial of HVAC-Calc Residential. Will that provide a decent enough estimate for now?

it's a good program

OK,
Here is my take on it. Info given:
House = 3700 sf of conditioned space including garage hydronic heat
You use 1000 gallons of #2 heating oil per year for heat and hot water
Electricity is 0.15$ kwh and your average usage is 800 KWH
1,000 gallons *138,000 btu/ gallon% 80% efficiency = 110, million btu/s per year for heating and hot water. This is what you have to generate with geothermal or some other means.
For the record a geothermal system with a cop of 3 would
Require 110,000,000 btus/ (3413 btus/kwh*3)= 10,750 kwh/year to generate this many Btu’s
10,750 kwh * 0.156 $/kwh= 1,676 dollars per year to heat with geothermal
This year you are going to pay around 3200$ for heating so potentially you could cut your costs in ½ with geothermal. Depending on installed cost this may be a good fit for you. The geo guys (I am not one) can give you a better feeling for this.
Here are some other possibilities:
You pay 3.15$ gal winter and 2.25 Summer (a 30% difference) My first thought is buy 2 more 330 gallon tanks and fill once a year in the summer when it is cheaper. This should cut your bill 15% which is a good start.
Your off season oil usage is fairly high which indicates to me you may have high domestic hot water usage. Look into a solar hot water heating system. Mine drops my usage of the propane boiler fired indirect in the summer to near zero. I would also make sure that the indirect tank is well insulated. If your family showers a lot and you have the room for it, a drainwater heat recovery pipe may be in order also.
The other thing to consider is your electrical bill is 1500$ per year. Trimming that by 1/3 would net you considerable savings. A thorough examination of electrical usage is in order. One thing that might help is low flow appliances and showerheads, since you are using costly RO water. Another thing is using a rainwater recovery system and cistern for part of your water usage, with the RO system for backup. Maine gets plenty of rain and you have a lot of roof area to collect from.
One further thing to consider is reducing the amount of heat you use. Do you really need to heat the garage? If so, garage doors are notoriously badly sealed. Can you make them more airtight? How about attic insulation and air sealing? Depending on what is up there, an overlay of cellulose, bringing the ceilings up to r50 or higher may be in order.
Note also that a lot of the things I am outlining above you should do anyway, even if you are going for a geothermal system.
Cheers,
Eric

Posted By eric anderson on 11 Feb 2011 02:27 PM

Your off season oil usage is fairly high which indicates to me you may have high domestic hot water usage.
Cheers,
Eric

I doubt very much this results from high domestic hot water usage.

Instead it is a result of the fact that keeping a boiler hot all summer just to keep an indirect tank warm causes the efficiency to plummet. The 80% you assume for winter (probably high as well) is likely well below 50% in summer operation. The boiler may only run 2-3 times per day for 10-15 minutes at a time. During the other 23.5 hours it loses heat out its jacket and up the flue.

If nothing else find a way to supply hot water via other means during summer and shut the boiler down completely

Curt,
You have a good point, oil boilers often have much larger hot water storage then gas ones, I looked it up and this one probably has 9 gallons of water in the boiler.
Lets say it fires twice per day and cools completely in between. Assume a 100 deg F temp rise *9 gallons*8 lbs/gallon*2= 14,000 btu/day wasted *180 days= 2.6 Million BTU/s per year. 2,600,0,000/ 138,000 btu/gallon= 18gallons of oil.
That does not account for the 300 gallons used in the non heating season.
OTOH my sister runs a 120$/month natural gas bill in the summer for DHW heating. Her boiler and hot water heater are separate. Of course they like their 5 gpm shower heads, body sprays, etc.

OK, if the system is 50% efficiency for summer dhw
0il at 3.00$/gallon would deliver (138,000* 0.50) /3 = 23000 btu/dollar
Electricity at 0.15$/kwh and there are 3412 btu/kwh so 3412/0.15 = 22,747 btus/ dollar.
So even if the efficiency of the boiler was 50% it is still around the same cost as using electric heat.
Seems to me like solar DHW with electric backup is a good way to go here if you keep the oil boiler. In the summer the solar takes care of DHW and in the winter, contributes some to the water heating, when you revert back to the boiler. The fact that you have a plumber brother to help you leads me to think this is a doable DIY project, which reduces costs dramatically.
Note that I am in no way saying that geothermal is a bad fit here, it may well be your best option, I am just throwing out possibilities.

Keep in mind that the 300 gal I am quoting in the "off season" also includes the time ramping up/down in the fall and spring where heat is needed periodically as well as summertime hot water. I also try to turn off the radiant zone in the garage until the outside temp is consistently cold to avoid the waste of periodically bringing the slab up to temp.

What seems to be coming more clear, is I am better off taking some steps to better prepare my house for cold weather (which shoud be done anyways) before taking the geothermal plunge. Although it is new construction and reasonably tight/well insulated, I can certainly blow some additional cellulose into the ceilings, add window quilts/inside storms, better plug the electric switches/recepticles, etc.

Thanks for the ideas - I still haven't passed on the geothermal idea, but I think I would be better served by taking the obvious steps first.

Conservation nearly always has better ROI than infrastructure.

I doubt an oil fired boiler operated solely to supply an indirect hot water tank is even 50% efficient in summer

A simple check would be to put an hourmeter on the burner motor, multiply it by nozzle oil flowrate