Did I make the right choice?

Eric Johnson_3

My 12-year-old A.O. Smith gas water heater cashed it in recently and after thinking about it for awhile, I decided to replace it with an electric water heater. I'm not sure I made the right choice, but here's my thinking:

An electric tank costs about half as much as nat. gas.

I heat all my hot water in the winter with wood;

My local utility gets most of its power from nuclear, hyrdo and coal;

Electric rates are less volatile than nat gas rates, in part because the PUC has to approve rate increases;

Currently, we pay about 12 cents per kwh and about $2.00 per therm;

Even though it may be more efficient, I don't see the cost of nat gas going down anytime soon.

Is there a flaw in my reasoning?

B. Norian

DHW

At the rates you quoted, it's a draw. With $2 gas, at 55 percent efficiency (about the norm for a direct-fired water heater), gas is costing you $36.36 per net million Btus. Electricity at 12 cents and 98 percent efficiency (skin losses from the tank), the juice is $35.87 per net million Btus. With hot water by wood in the winter, the cost premium for electric DHW is minimal.

Mike T., Swampeast MO

Revised gas WH efficiency down to 65%. Energy factor of .60 seems fairly common for inexpensive gas water heaters and .95 for electric. I'm using the difference .35 (65% efficiency) and neglecting the standby losses that keep the electric from having an energy factor of 1.0

On a purely cost-of-fuel basis:

100,000 btus (one therm) of energy from electric @ 12¢ kw/hr = $3.48

100,000 btus of enegy from gas @ $2.00 therm and & 65% efficiency = $3.07

Say you need 15 therms/month for DHW for 7 months of the year. Factoring in the efficiency drop for the gas heater cost per year will be $322.35 for gas and $365.40 for electric.

Say both types last twelve years: $4,372.80 for electric; $3,868.20 for gas. Difference of $504.60. Not a whole lot of difference, but the gas does seem a bit more cost effective.

If efficiency of the gas water heater is as bad as 55% then cost per therm of usable heat with gas goes up to $3.64

Ted_13

HPWH

Eric, I've read that heatpump hot water heaters are 3-5 times more energy efficient than electric resistance water heaters and they can also provide a source of cool air to your house in the summer time. I'm sure they must be more expensive than an electric resistance heater however.

Eric Johnson_3

That's interesting.

I'm betting that the price of nat. gas is going rise over the next decade more than the price of electricity, based on the fact that my local utility uses less than 25% natural gas in generating its electricity, and no fuel oil.

Maybe I'm a victim of wishful thinking.

All the more reason to get my **** in gear and put up some solar collectors.

BTW, I live pretty far north, so I'm running the wood-fired boiler probably 7 months out of the year. During warmer weather it doesn't take much wood to keep the water heater tank full of hot water.