water heater - oil vs. electric

cahill98September 13, 2007


I currently have a small hot water tank that is being heated from a loop to the boiler. The tank is too small and we would like to get a larger one. However we are thinking of switching to an electric water heater because it seems really inefficient to have the boiler going on and off all summer just to keep the hot water warm. So I have a few questions questions:

1 - will the install cost significantly more to switch to electric?

2 - will electric cost more or less to operate?

Current rates in my area are 2.38 a gallon for oil and about 7 cents a kwh for electric. Some calculations I found online seem to have it coming out about the same - however, over the past 4 months we have not turned on the heat but have still used about 75 gallons of oil - that works out to about $45/month to heat the hot water. I read that an electric hot water heater uses approx 283 kwh a month to operate which works out to about $20 a month (not sure how accurate the 283 estimate is?)

3 - what other pros/cons should I consider (i.e. wait time for hot water/cost of tank/life of tank)


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if it is costing you 45 a month to heat the water during the summer, then yes, a regular electric WH would come out cheaper during the months that you do not have the boiler going.

i wonder if you could have a dual system, use the electric during the summer, but shut it off and feed it from teh existing system during the months the boiler is usually going? then again, at 7c per kwh, it is not going to cost that much to run the electric year round.

    Bookmark   September 13, 2007 at 1:44PM
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I took a standard electric water heater that the Energy Guide says will cost about $411 a year at 8.6 cents per kwh and converted that to 7.0 cents and came out with an estimate of $334 per year.

The estimated number of kwh per year for that same scenario is 4779 kwh or about 16310727 BTU's

number 1 fuel oil is about 134,000 per gal and If we guess the burner is 50% efficient in the summer it comes out to about 243 gals of oil for the year or $579.

Your stated use is $540 a year so I'm guessing my calculations aren't far off.

So: You could reasonably expect to pay $334 for electric (or a little less) or about $540 for oil.

Now, you would need to get an estimate on the installation of an electric heater. I would recommend that you get one with 2" of insulation (fairly mainstream) and add a blanket to it for $20. This is much cheaper than buying a super insulated heater. A 50 gal GE "Energy Smart" heater, for example, is $340 at lowes. (that's not an endorsement-- just an example) For a small family, 50 gal should be fine unless you have a large tub, for example.

Your installed cost will be higher because you will need to have the electrical run to the heater.

Nonetheless, the savings will be about $200 a year and you will have hot water.

I wouldn't put much more thought into tank life, etc. It will last about 12 years. When it's time to replace it, the replacement cost will be much less because the plumbing and electrical will be in place already.

Here is a link that might be useful: Electric water heater

    Bookmark   September 13, 2007 at 3:35PM
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I would replace the existing tank with an electric water heater. Shut the boiler off in the summer and let the electric do it all and in the winter feed the electric water heater with hot water from the boiler.
Nothing to switch

    Bookmark   September 13, 2007 at 6:05PM
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"I would replace the existing tank with an electric water heater. Shut the boiler off in the summer and let the electric do it all and in the winter feed the electric water heater with hot water from the boiler."

Even if the boiler is 70% efficient in the winter they would still pay more for heating with oil. It would have to be about 90% efficient to break even. There's no way the boiler is approaching anywhere near 90% -- even in the winter.

Keep it simple and cost effective. Just move it to electric all year.

    Bookmark   September 13, 2007 at 10:31PM
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Thanks everyone. Electric seems to be the most straight forward and economic solution.

    Bookmark   September 14, 2007 at 10:51AM
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depending on your habits, you may want to install a timer, that only runs the water heater at certain times of the day. we put one in and saw an immediate drop in our elec bill, as well as the insulation that was mentioned earlier.

    Bookmark   September 17, 2007 at 1:22PM
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The principal has heard about clean energy and the Eskom solar water heating rebate programme and would like you to explore fuel switching. if the 1,000GJ of oil were replaced with renewable energy (solar) how many litres of oil would be save and what would be the cost savings ? What other benefits would be derived through implementing this intervention ?

    Bookmark   March 11, 2011 at 7:04AM
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