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electric vs oil hot water

Posted by tjg911 (My Page) on
Fri, May 16, 08 at 12:39

i read a thread from last year that i found via a google search. it was from someone here in ct but the prices are so out dated going back almost a year.

are there web sites where i can compare the cost to heat hot water with an electric hot water heater at X cents per kWh vs using heating oil at $X.XX per gallon?

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if anyone would like to comment here are my specifics:

i heat my house with wood so i may run the furnace ONE or TWO times per year for heat, often ZERO times per year so all my oil is for hot water. this is a new house built in 98-99, oil fired hot water base board radiators with a 'mega store' highly efficient (?) hot water storage tank. i do not want to generate hot water via wood.

i use 250 gallons of fuel oil every 16-17 months. there's just one person here and i am very conservative with hot water.

fuel oil is now about $3.80 to $4 a gallon, last time i filled the tank (275 gal) it cost $2.35 a gallon.

electricity has lots of charges but if i total them all my cost per kWh is $0.1668 plus a flat fee of $15 for 'distribution customer svc chrg'. last month my bill was $73.04 for 348 kWh and that is typically what i use.

so since i pay that $15 distrib servc charge anyway, if i heated my water with an electric heater it would be 16.68 cents per kWh.

i strongly suspect electricity is much cheaper than fuel oil at these fuel oil prices. however, the cost to buy and install a electric hot water heater would take some time to recover via the savings. even tho i almost never use the furnace, it seems that removing the 'mega store' tank and buying an electric water heater is spending money unwisely.

so how do i find the cost to heat water for a year using electric at 16.68 cents per kWh vs $4 for fuel oil?

thanks,

tom


Follow-Up Postings:

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RE: electric vs oil hot water

saw something similar to this in a post on another thread.....

1 kwh of electricity produces 3,412 BTUs of heat.

1 gallon of propane produces 91,200 BTUs of heat.

1 gallon heating oil produces 139,000 BTUs of heat
(above info found here: http://www.eia.doe.gov/kids/energyfacts/science/energy_calculator.html)

139,000/3412=40.74 so it takes 40.74 KWH to get the equivalent heat of one gallon of heating oil.

Using information above and calculation below substitute your cost per kwh of elec and per gallon of heating oil and you can find which is a better option. (my costs are the current ones in the formula).

40.74 KWH @ 6.5/KWH=$2.65 & 1 gallon of heating oil at $3.50/gal. Therefore, $2.65 (to $3.50) worth of electricity will give you equivalent drying BTUs that $3.50 worth of heating oil will give.

Here is a link that might be useful: BTUs produced by these fuels


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RE: electric vs oil hot water

almost forgot to add to above message....
some heat from gas and oil waterheating will go up the flue and not be used to heat the water. Whereas all heat produced by electric water heater is used to heat the water so if cost between elec and oil OR elec and gas were exactly the same, you'd still be better off w/ elect due to loss of heat up flue from oil or gas. 1


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RE: electric vs oil hot water

I live in the North East. I have a new oil fired boiler (1 year old), forced hot water system. It has 4 zones, one of which is for my domestic hot water tank. The boiler will only fire if the aquastat is below setpoint and there is a call from any zone, so it does not run to maintain a boiler setpoint (which is good). With the price of home heating oil averaging $4.75 a gallon, I am taking some steps to cut back on costs. One of which has been the recent purchase of a Pellet stove. I plan on this being my primary means of heating my house. I am questioning whether or not to install an electric hot water tank as my primary source of domestic hot water instead of my indirect domestic hot water tank. I have asked around, both via associates in the trade and reading the online forums. Pretty much everyone seems to believe electric hot water is cheaper. I want to believe that is true, but my calculations tell me other wise. I could be overlooking something, I sure hope so. Anyway, please review the following and advice. Thanks

Home heating oil produces about 140,000 BTU per Gal
My boiler is 84% efficient, which yields me 117,000 BTU per Gal.
Heat losses due to piping etc I cant calculate, so I will stretch a guess and say 10% heat losses. So now I yield 105,850 BTU per gallon.

Circulator pump and Burner motor running consume 2.41 amps combined, consuming .2892 KWH @ $.18415071 per kwh = $.05 an hour to run. (is that right?)

So to get the 105,850 BTUH from a gal of oil it costs me $4.75 + $.05 for pump and burner run time for a total of $4.80

Now to get the same 105,850 BTU from an electric hot water tank, and figuring electric heat at 100% efficiency ( I realize its probably more like 97% in reality).
1 KW = 3,413 BTU.
So 105,850 BTU divided by 3,413 BTU = 31.01 KW needed to produce the 105,850 BTUs
So 31.01 KW times the cost of $.18415071 per kwh = $5.71.

My calculations here tell me to get 105,850 BTUH from my oil burner cost me $4.80
My calculations here tell me to get 105,850 BTUH from Electric hot water tank cost me $5.71. What am I doing wrong here? Thanks


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RE: electric vs oil hot water

Upon quick view, it seems that your calculations are correct. I think the issue is that your cost for electricity is probably one of the highest in the nation (my guess). Same amount of kWh for me would cost $2.01 (midwest).


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RE: electric vs oil hot water

The heat loss up the flue of an oil fired boiler is significant -- in the range of 30-35%. An electric resistance water heater is about 99% efficient.

Thus it only takes about 27kwh to equal the usable heat value of 1 gal of oil.

Something to be aware of is that energy is largely substitutable (as you are figuring out). Thus the forms of energy that are easy to substitute will eventually reach an equilibrium price... meaning that electricity (and natural gas and propane)should also increase in price.

That doesn't mean that you shouldn't switch... it means that you shouldn't base your payback calculations on the current energy price differentials lasting for too far in the future.


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