Electric vs. gas water heater? Which more efficient?

[Pskhaat]

So I live in a place where at night 9pm->9am I get like 4-5¢/kwh for electricity. I also live in the desert where I can basically shower with no hot water as the cold water from the street is just plain warm.

I'm paying slightly under $3/therm from our rip-off natural gas company (my only choice).

By my calculations it is way cheaper to run electric water heater, would you not think?

 

[Blue 60]

tough choice

Gas water heaters are normally much more efficient. Electric water heaters are "greener". (Better for the environment...) Elec. water heaters are slower to recharge their tank of hot water after showers/baths. Where I live, the city gives a big discount if your house is all elec. In you case, elec. looks to be cheaper in the long run.

Blue 60

 

[Pskhaat]

I've done the topical calculations on efficiency too for NG heaters, BUT it still amazes me how much heat actually goes out the flue.

I couldn't go tankless due to the location of the heater in the house but it is a new "efficient" model (wouldn't you want your heater to be the most ineffecient )

 

[Blue 60]

efficient

No, you do want it to be efficient. It's like your car, you want the most miles per gallon. With the water heater, you want the most "heat" (btu's) per Kwh (Kilowatt hour for elec. water heaters). To increase the efficiency, you can put a thermal wrap around the tank to retain as much heat as possible.

Blue 60

 

[FJ40_owner]

Making hot water from electricity is the most efficient by far. You convert more energy into hot water using electricity.

Wind turbines use a dump load and they typically connect to a heater element.

The best question is how much do you pay for a unit of energy. The gas should be much cheaper to make a difference.

If I paid .03 - .05 per KWH I would heat, cool, cook, have a spa, a heated pool and air condition my garage with AC. Are you sure about those numbers.

I pay .15 for my first 100 KWH/month then I pay .38/KWH. It gets very spendy where I live.

 

[Pskhaat]

You can read the rate card here: APS ::Rate Pricing

OK, rates went up but yeah at night I pay roughly 5¢/kwh plus a daily charge. We can use a gigawatt-hour/mo easily with our AC needs and we keep the house no lower than 82ºF, often at 86-87ºF.

 

[e9999]

in places where electricity is made with NG, the cost of electricity energy is bound to be 3x more than the cost of gas energy, if there is no futzing with the market. That's because the efficiency of a power plant is about 1/3. Fossil fuel Elec is inherently much more expensive than primary energy.

If made with coal, it's cheaper elec but still not as cheap as gas per unit energy. If you get electricity much cheaper at night, and gas prices are tweaked, all bets are off.

Basically, you should look up the price of your electricity. Convert to Joules or Btu or kWhr or whatever. Efficiency of your electric heaters is about 100% if well insulated.
Do same for gas, convert. Then divide by efficiency of the gas heater [edited: don't know the value for water heaters].
Compare.
Decide.
Enjoy.

 

[titanpat57]

No, you do want it to be efficient. It's like your car, you want the most miles per gallon. With the water heater, you want the most "heat" (btu's) per Kwh (Kilowatt hour for elec. water heaters). To increase the efficiency, you can put a thermal wrap around the tank to retain as much heat as possible.

Blue 60

I agree...wrap the heater with a good insulation kit and install a timer. If the water from the curb isn't ice cold then have a timer kick it on before you get up and kick off an hour after leave for work. Do the same for evening dishes and showers. Almost all parts are replaceable and with a little maintenance you can enjoy many efficent years of service.


Pat

 

[EdsCruisin]

If anything other than the price of service is of concern, the gas heaters are typically much faster than AC (important with teenage daughters in the house) and you also need a flu for the gas heater, whether conventional or high efficiency.

 

[Toyo FJ40]

Like FJ40_owner said at that price per Kw I would do electric. Electric is the cheapest to install from a plumbing stand point and you have the option to easily move it if you have to. You need to get a larger tank to make up for the slower recovery but an 80 gal will do a 3 bath house. Electric are easier to wrap than gas water heaters to improve heat loss. Efficiency really doesn't come into it because there's no wasted heat out a flue like there is with gas or oil.
If your price per Kw changes at differant times in the day you can put a timer on the heater so it only heats at the cheaper times.


Kevin

 

[RavenTai]

Is the water heater the only natural gas appliance? in ATL there was a hefty base charge before you you buy the first therm. if so it may make sense to go electric if you can get rid of the gas bill, even if electric costs more per btu overall cost could still be less.

but if you heat your home with natural gas you might was well heat your water with it also.

 

[Pskhaat]

Yes, there are base charges and yes our HVAC house system is gas, but luckily (or unluckily) where we live we don't need heat. I'd clearly have to keep all the lines and meter for whomever would own the house next.

 

[RavenTai]

If you can shut off the gas that combined with your cheap electric prices I bet you will be ahead.

I assume you are asking because the gas heater is dead/dying and needs replacement anyway?

I recently swapped mine from propane to electric, the price of propane got stupid. $4.10/gal. And then they started charging monthly service fee, before it was just the $250 or so when the truck came and filled up the tank. The electric water heater cost less refilling the propane tank, $10-$15/month more on the electric bill vs $200-250 twice a year + $9/month service fee. and do not have to let the meath head looking propane truck drivers on the property eyeballing my tools.

the electric heater does have a longer recovery time, the propane heater would basically keep up real time, same with my natural gas heater in ATL, but the new electric you can run out and take a while to get hot water back. not a problem here but with many people in a home it might be.


look into turning your old gas water heater into a solar batch heater, very cheap way to get solar hot water. I'll bet where you are at with a batch heater the electric heater would not turn on during the day.