Electric hot water - real world numbers?

[Alan Gage]

In preparation for building this spring I'm considering my appliances and have been thinking about hot water the last couple days. I already have a propane tank on property and since gas is the cheapest to run I originally planned on buying a direct vent water heater. Just out of curiosity I called the electric cooperative to see what incentives they offered for electric appliances and their incentive is selling a (what they claim) $700 water heater to the customer for $200 with a lifetime warranty. I've yet to go down in person to look at the water heaters they supply and get the specs on them, nor do I know just how legit the "lifetime warranty" is yet. But it got me thinking so I started snooping around online to try and get an idea operating costs between gas and electric.

I started finding some numbers that were lower than I expected for yearly costs for the electric heater and made it sound pretty attractive. Since a direct vent propane would probably cost me an extra $600 out of the gate it would take quite a few years of energy savings to pay off, and by then I might be due for a new one.

So I asked my sister, who is single (as am I) and uses electric hot water, how many Kwh she uses a month and was astounded to hear it's over 1,000. She does a lot of laundry but says she only washes with cold water, the drier is electric though. She's got a water heater for her horses plugged in all the time but I wouldn't think it would add that much. Even if the water heater was only half of that it still seems like a lot. She doesn't know the age/condition of her water heater and I haven't looked at it either, so maybe that's part of the issue.

Anyway, what she's experiencing and what I'm finding online are very contradictory so I thought I'd pose the question here to try and get some more real world answers. What can I expect from a new, well insulated. electric hot water heater?

About my hot water usage:

I'm single and use very little water, especially hot water. I've been running a propane hot water heater the past few years and I think I go through about 100 gallons of propane/year. The kitchen stove and hot water heater are the only things running off the tank. In the summer I take a short (and usually cool) shower everyday. In the winter I might take 2/week but they're usually long and hot. No dishwasher and I wash my clothes in cold water.

One other benefit of the electric would be not having to pipe the exhaust outside, which I suppose isn't quite such a big deal with the direct vent.

Any input/advice appreciated.

Alan

[archimedes]

I wondered the same thing so I did an experiment.

I purchased one of these;   http://us.element-14.com/jsp/search/productdetail.jsp?SKU=78H0980&CMP=AFC-GBE14
and connected it to the heating elements on my electric water heater to determine how long they were actually using electricity.

Let me first say that I live in a two person household.  But we don't use a lot of water,  probably not much more than you.

What I found was that the electric water heater only used about 40 - 45 kw a month.  Much less than I expected.

What was even more surprising was how little electricity it used in "stand by mode".  Unless I was using hot water, the water heater hardly ever came on - unlike what the sellers of instant hot water heaters want you to believe.

So for my 4500 kw electric water heater @ 13 cents per kwh I was paying between $23.40 and $26.33 per month for hot water.

Again,  much less than I expected.  So it would take quite a few months to recoop the cost of a more expensive but more "efficient" means of heating your water. 

Even if you were able to shave 30% off that number (questionable) with a more "efficient" system,  what does that save you,  maybe seven bucks a month?  That's an aweful long payback period.

I hope this helps.

[JRR]

I currently use natural gas and electricity in my home.  Haven't really studied the numbers, but think if my house were modern and efficient ... I would be better off being "totally electric".  The gas and electic companies both charge base-line service charges.  It would be nice to do away with one of them. 

Currently, in this large poorly insulated thing, the quick start up/recovery of gas heat is nice.  And the gas company is quick to send a service guy to check for leaks ... which they routinely do every few years on their own.  This is something you may not have using propane ... depends on your suppliers policy.  I have known of a couple of families, using propane, who have blown up their houses ... something to put in the equation.

Overall, I think electricity is a bit safer than gas for heat and lights.  With proper constuctiion, it may be the better buy.

I think both my utility companies offer life-time warranties on appliances bought from them ... easy to see why.  They are in constant marketing war for customers.

[davidj]

For a storage-type water heater (i.e. ignoring on-demand), an electric heater should be considerably more efficient than a gas heater.  For the electric heater, you have a vessel surrounded by insulation, with some wires going in, an inlet pipe and an outlet pipe.  Pretty much all of the electrical energy ends up as heat.  And you can insulate that setup really well, so not much loss if you just heat it up and hardly ever use it.  For gas, you've got the complication of a gas flame, which requires fresh air to come in and vent gases to escape - makes it hard to wrap it all in 6" of foam!  And if the vent gas is warm, then that's wasted energy.  There are ways of making gas more efficient, but they are also more complicated and hence more expensive.  So, with gas, maybe 20% of the energy (with a cheap heater) is disappearing up the chimney and more is wasted when not in use due to less effective insulation.

However, for a given unit of energy, gas is typically cheaper than electricity.  According to the interwebs, 1KWHr = 0.034 therms.  With PG&E, 1 KWHr of electricity costs about $0.12 (baseline), but 0.034 therms of gas costs $.03 (baseline @ $.92/therm).  Last winter, the average US cost of propane was $2.62/gallon and one gallon of propane is 0.92 therms, so 1 therm costs $2.85 and 0.034 therms cost  a bit under $0.10.

In summary, for one KW of energy around my parts:
  Electricity - $0.12
  Gas -         $0.04
  Propane -   $0.10

I.e. in Northern California, using gas works out maybe 1/3 of the price of propane or electricity.  But if you're using propane, electricity isn't a bad deal as it's a similar price once you take into account the typical efficiency of low-end appliances.

PS apologies if my math is wrong, and also note energy prices vary greatly by location and over time.
PPS when it comes to on-demand, generally go with gas as the current requirements for electricity require an oversized electrical service and some very big wires as Glenn and others have mentioned elsewhere.

[Don_P]

You can also put a timer on the electric and drive it's operating cost down a bit more. In Norway my sister lived with a family that had the hot water heater on a dial type timer switch, when you wanted hot water you turned it on, it would turn the heater on for about a half hour and heat a tankful...makes a good bit of sense.

[Alan Gage]

Thanks for the input all! I'm leaning very heavily to electric. I think it will take a lot to swing me back over to gas. I did some more poking around online and found some nice calculators for house/appliance efficiency and for my low usage there just isn't much of a savings by going to gas. I doubt I'd ever save enough to make up for the higher cost of the gas heater. Research is good. Originally I'd dismissed electric out of hand as being too expensive based on what I'd heard over the years. Just hope I didn't outsmart myself.

Some links to a couple of the calculators in anyone is interested:

http://cbpower.apogee.net/homesuite/calcs/rescalc/default_supp.aspx

http://www1.eere.energy.gov/femp/technologies/eep_waterheaters_calc.html

And a link to a page with a bunch of different energy calculators:

http://www.ilec.coop/aspx/General/PageGroup.aspx?PageGroupID=2&n=533&b=3

Alan

[Lifer]

Have you considered one of those flow through electric water heaters from GE?

The unit costs about $150 dollars and only uses electricity when it is heating the water that you are actually running through the heating unit.  The rest of the time the unit is on standby... just waiting to warm up the water when you need it.

We have had one for the last 15 years and it's great.  You can easily set the water temperature you want.

I think it saves on eletricity costs since it isn't working unless you actually have the hot water on.

Anyway, it is something to think about.

[MountainDon]

Here's something interesting ...

http://pressroom.geconsumerproducts.com/pr/ge/doetanklesshybrid.aspx

It's a tank type heater with a heat pump. The heat pump absorbs heat from the surroundings and is transfered to the water in the tank. Much more energy efficient than heating the water with a resistance heater element(s).

[OlJarhead]

The only question I have is this:  is solar in your future?  If so electric water heaters are either out or nearly out.

For me it was a no brainer -- propane instant on.  Why?  No electricity required   Also, the initial outlay was ok ($640 for Bosh unit I'm thinking about) but super cheap to run thereafter.  Since we're unlikely to use the cabin more then once or twice a month (just too far to drive every weekend) we're unlikely to use the hotwater often enough to warrant an electric unit.

[muldoon]

Another factor you may consider.  In my experience, electricity is spotty.  I can think of storms that knocked the power offline.  When Hurricane Ike blew over us we were without power for almost 2 weeks.  Natural gas continued to flow the entire time.  Just a datapoint to consider. 

[Shawn B]

I agree with muldoon. It's hard to beat natural gas (or propane) for reliability. Where I live we loose electric several times a year, either thunderstorms or ice/snow storms. It's nice not to have to depend on electric to heat water. It's real nice to be able to take a hot shower even if the lights are off and nothing is running. Yes we have a generator and our house is wired for easy hook up, but sometimes it's more trouble than it's worth messing with the gen when the power will only be off  12 or so.

[Alan Gage]

Those water heaters utilizing heat pumps look interesting, I saw a few of them when I was looking around. I haven't talked to anyone who's actually used one though to see how they stack up.

There are no alternative energy sources in my foreseeable future. There's no payback for me at my current usage and power outages are a rare occurrence here. It's cold enough in winter we don't get many ice storms. I don't ever remember the power being out for over an hour.

Lifer - Are you talking about tankless on demand water heaters or something different? I considered them but again the cost was considerably more than what I could get an electric tank heater for from the electric coop and there just isn't that much savings considering my small amount of usage, at least according to online calculators and some personal feedback I got. It will be interesting to see how it really pans out.

Alan

[MelFol]

We are building in Alaska http://countryplans.com/smf/index.php?topic=10054.0 and I worked through the same question.   I researched the demand water heaters and found lots of complaints, so decided to stay clear until the bugs are worked out better. The exception is an oil fired demand water heater. I have several friends with them who have had zero problems after years of use.

My options were Propane, Electric, or Stove Oil.   I looked at it strictly in terms of BTU's. You could convert everything to KWH equivalent like David, but I stayed with BTU because a BTU is the amount of heat necessary to raise a pint of water one degree F..  So the number of BTU's of each you can buy for a dollar would give an indicator of best value.  The calculation went like this:   (BTU's per gallon or unit x efficiency of the appliance) divided by cost  would give me the # of BTU's per dollar.  Here is my example from our area in Alaska:

LP has approx 91600 BTU's per gallon.   (91600 x .63)/$5 = 11542 BTU's per dollar.

Electricity has 3412.3 BTU's in a KWH.  
3412.3 BTU per kwh x an efficiency of 0.93 / 21¢ a KWH =15112 BTU per $.  (Yeah, electricity is expensive up in our remote area).  

Fuel oil/stove oil has approximately 138700 BTU per gallon (some sites say up to 141000. The more viscous the oil the more BTUs. I went with the lower number).  
So 138700 BTU x 0.88 (the efficiency of the fuel oil fired water heater I am considering) /$4.25 (cost of stove oil up there) = 28719 BTU per dollar.  

According to that fuel oil is nearly twice the deal of electricity, and 2.5 times cheaper than LP for us.