Heat with Noil (No Oil) or Soil (Some Oil) ??? Cheapest

Ok, here is the situation.
Wood Pellets are used for heat so this Question pertains to DHW or Domestic Hot Water?
I heated the 40 gallon SuperStor last night for 45 mins to bring it up to 130 Deg F.
Then I switched the boiler off and changed the flow valves to pull that 130 Deg F Water into the EcoSmart 24 On Deman Hot Water Panel.
The water stayed warm all night so in the morning when the EcoSmart 24 pulled the SupperStore water for the shower, a very minimal # of amps was used if any!
The current meter showed only a total of 4 amps during the shower when cold water from the street would need a total of 92 amps to heat the water to the setting of 135 Degrees F for the shower.
The efficient Buderus boiler with a 0.65 GPH nozzle used roughly o.5 gallons of oil at $1.70 per gallon so approx $o.85 or 85 cents

The duration of the shower approx 15 mins
The liberty utility rate for Salem NH is
14.02 KWH
See
https://new-hampshire.libertyutilities.com/uploads/Rates and Tariffs/Electric 2019/Summary-of-Rates-GSE-Jan-2019.pdf
Now Single phase AC power is
P = PF x I x V / 1000. Where PF = Power Factor
And I = AC Amps and V = AC Voltage
In this case
There are 2 amp meters on the circuit box, 1 meter on each 120 VAC leg. I saw about 46 amps on each meter. So 46 + 46 is 92 amps at 120 VAC
P = 1 x 92 x 120 = 11 KW
Therefore:
17.00 x 11 = $ 1.87 for 1 house shower
So 15 mins is
$1.87 x 1/4 of an hour = $0.46.75 or about 47 cents

Therefore using Noil or No Oil
Using On Demand electric for heating hot water saves:
85 - 47 = 38 cents

Are these calculations correct??
How about heating the water to 90 degrees with oil and the test with electricity??

Actually the oil leaves 110 degrees worth of hot water in the 40 gallon tank that only needs a little more oil to heat subsequent showers so the savings is not so dramatic after a few days?

 

BTW, that $14.02 is your customer service charge. Prob on a per month basis. Looks like your per KWH charge is either $0.16475 or $0.17059 depending on your use. Ours is closer to $0.20. Not sure of the reason for the difference.

Also, is your on demand heater 120v or 240v?

 

Thanks for the correction!! I just fixed the calculations
The On Demand is 3 - 40 amp breakers at 240 volts each.

 

I have the EcoSmart. Mine takes (3) 40amp 2 pole breakers and pulls up to 112 amps

 

I would love to preheat my well water before it goes to the EcoSmart

 

Ok. So 92 amps x 240 volts is 22 Kw if my math is correct.

 

Could you at least run your water through some kind of radiator to heat it to room temperature prior to going to the eco smart? Kind of using the radiator to absorb heat instead of radiating it.

 

No I have 2 amp meters on the circuit box for each 120 volt leg.
So using the On Demand Panel pulling cold street water I saw about 46 amps on each 120 VAC leg.
So that would be
92 x 120
Or
46 x 240
Either calculation
Is 11 KW

 

Got it. Makes sense.

 

If you have a warm basement then just get a storage tank. The basement heat will warm it up.
You can also point a pellet stove at the storage tank like in my basement. I get the tank up to 80 degrees with wood pellets!!

 

Thats a thought!
Will a rad take 65 psi?

 

My wood stove is in the basement. That room routinely get up to 84-90+ degrees.

 

Can you hang the storage tank up near the ceiling?

 

I thought that also. I remember my grandparents house had a rad in the basement under the kitchen floor. That would be perfect

 

I think that is a critical variable in your calculation. The next thing to consider is when that hot water would be needed again. If the hot water is used so infrequently that the water in the 40 gallon tank returns to room temperature then your savings calculation above would be correct. If the next time you heat the water with oil, you didn’t have to use as much, your savings would be less...

For the first couple years here, I shut down my boiler to save money and only fired it up when we needed hot water for showers.. we saved a few bucks by not having the boiler up to temp all the time. In doing this, we also temperature shocked the zone valves causing 2 of them to leak and incurring a $400 plumbing bill.... since that time, the boiler has stayed on and I have accepted my $50 per month cost of oil for hot water (figured at $3.00 per gallon). If heating oil is less than that, I’m saving enough each month for a couple cups of coffee..

Perhaps you can approach this analysis from a perspective in which you calculate BTU’s instead of KWH.

 

Yes, I totally agree! Turning the boiler off and on too much can really take it’s toll !!
Withmy setup, I do not need to turn the boiler back on so I have the boiler off. It is a very expensive beast to maintain and maybe I am better off without it, even though I installed seperate circulatory instead of zone valves for durability and I can change them myself!

 

don2222 have you thought about using a heat recovery drain? I have no experience with them but looked into them a while back. I think it would work best with a high use individual appliance (like one shower) and installed on the cold water supply pipe. I guess the theory is that your shower has a mix of hot and cold water. If you preheat your cold water, you can use more of it and therefore less hot water. Would take some calculations to figure out the savings. I imagine you’d have to do the install yourself on a residential install to make your money back in a reasonable amount of time. Here’s a pic and a website.

RenewABILITY Energy Inc. - Home of the Power-Pipe Drain Water Heat Recovery System

 

You really don't want to store potable or even bath water at room temperature. Too many kinds of bacteria love the culture temperature.

If I use my official utility rate for electricity I'd be using a factoe of $0,12 /kWh.
But that is NOT what I pay for electricity. I have to add in the delivery charge and the monthly bill charge because you can not NOT pay those amounts.
I take my monthly bill of $35.49 / 120 kWh and my actual electric rate is $0.296/kWh
We don't have tier rates yet to fudge up the math.

My Buderus boiler has a .40 nozzle and sips oil to make and store hot water.
I'll use oil at $2.30 / gallon thank you very much.

 

I checked into that also and it just does not seem to recover much heat to make it worth while.