Heating...gas vs. electric

[Dr. Spa™ Ret.]

Sorry, couldn't find the post this was started in...

Got my power bill so I though I'd do a proper cost comparison  

Here in CA electricity rate are tiered. The more you use, the more you pay.


For me, electricity is tiered at;

Baseline (first 294Kwh) @ $0.11536 per Kwh
101% - 130% of baseline @ $0.13115 per Kwh
131% - 200% of baseline @ $0.24711 per Kwh

Gas is tiered at;

Baseline (first 19.69 therms) @ $1.09076 per therm
over baseline @ $1.32871 per therm

The conversion formula is;
1 therm = 29.300111111 kilowatt hour

Working off the lowest rate, which is probably on the LOW side considering I'm into the upper tiers before the spa...

1 therm of gas @ $1.09 gives 29.3 Kwh worth of electrical energy

29.3 Kwh of electricity would cost $3.38

In addition to this difference, there's the electrical cost of operating the pump required to move water through the heater. Since a gas heater will heat the water 3 to 6 times faster than an electric heater, additional savings will be realized with gas heat since the pump wont need to run as long to heat the water (though, this particular savings could be quite minimal as the pump still needs to run long enough to properly filter the water anyways. e.g it may need to run just as long on a gas heated spa to filter the water, as it would on an electric heated spa to heat the water) .

[Water Boy]

[Dr. Spa™ Ret.]

CORRECTION  

I forgot, gas heaters are only about 80% efficient (electric heaters 100%). So...

The corrected conversion formula, based on efficiency is;
1.25 therms of natural gas = 29.300111111 kilowatt hours of electricity

In my case, $1.36 of gas will provide the same amount of heat as $3.38 of electricity.

1 therm of gas @ $1.09 gives 29.3 Kwh worth of electrical energy

29.3 Kwh of electricity would cost $3.38

[Shaamus]

let's build one Doc!

[zroger73]

Also, keep in mind that electrical resistance heating is virtually 100% efficient. Gas is faster because you have more input BTUs, but the efficiency will vary greatly depending on the design of the heat exchanger. The best heat exchangers can reach 98%, but that's typically limited to high-end, premium efficiency furnaces. I would expect a much lower efficiency for a pool/spa heater that will narrow the gap - perhaps greatly. I'm not selling fuel or electricity, just pointing out there are a more things to consider than just comparing the prices of quantities and units.

EDIT: While I was typing this post, you remembered the efficiency difference between gas and electric.

[Shaamus]

The other thing about natural gas is that it isn't viewed as a "manufactured" energy source.  Whereas the CEC is looking at energy generation capacity and is trying to force people to use less to lighten up on generation demand, switching to a energy source that doesn't require power plant generation is not going to be bothered by their efforts.

You better watch out CA residents who don't cook with gas.  They'll come after your electric ranges next!

[D.P. Roberts]

Here in CA electricity rate are tiered. The more you use, the more you pay.


For me, electricity is tiered at;

Baseline (first 294Kwh) @ $0.11536 per Kwh
101% - 130% of baseline @ $0.13115 per Kwh
131% - 200% of baseline @ $0.24711 per Kwh

Working off the lowest rate, which is probably on the LOW side considering I'm into the upper tiers before the spa...

Wow, that's crazy.

Here in Ohio, I'm paying $0.73 per KWH (before taxes), with no tiers.

What happens above 200% of the baseline?

Even at $.24 per KWH, I can see a spa costing over $500 a year in electricity. No wonder California's getting all uppity about efficiency.

[Dr. Spa™ Ret.]

What happens above 200% of the baseline?

According to their website, which differs slightly from my bill;

Baseline Usage - $0.11531 per Kwh
101% - 130% of Baseline $0.13109 per Kwh
131% - 200% of Baseline $0.25974 per Kwh
201% - 300% of Baseline $0.37866 per Kwh
Over 300% of Baseline $0.44098 per Kwh

[zroger73]

I'm told we have some of the least expensive utilities here in East Texas, but I've never seen any comparisons. Over the last three years I've paid between $0.07 and $0.10 per KWH mainly depending on the season (gets higher in the summer). My 46 year-old, 1,300 sq. ft. brick home costs me about $150 monthly in electricity and natural gas combined. I've haven't noticed any dramatic increase since purchasing my hot tub since last June.

[stuart]

So I like what you've done here Doc but there are a lot of other factors....
 
The cost of a gas heater for most consumers is up to 10 times the amount of buying an electric one. The heat exchangers have traditionally been very fragile to the water chemistry conditions and very expensive to replace.  
 
So how do you factor a $900 gas heater vs a $30 electric one then factor the $400 replacement for the heat exchanger every 4 or 5 years? Then you have to add the replacement cost of the heater every 8-10 years.
 
My best guess is that with those costs involved an electric heater will be simpler and less maintenance.  
 
Don't get me wrong, I would rather have gas because of the speed it heats at but it's not sensible for me.