Energy Efficient Water Heaters
Right now we have an 80 Gallon electric water heater in a heated area of our home (now that our hot water hogging kids are gone we probably don’t need the 80 gallon unit). We live in the Pacific Northwest and are not on a Natural Gas line. My wife has been reading about energy efficient water heaters and wants me to consider replacing ours (which must be 15-20 years old but is still working just fine) with one of the more efficient models. My take on heating water is that it takes so many watts of electricity to heat so many gallons of water so many degrees and it doesn’t make much difference how you use those watts there is little difference in cost. And further that most “energy efficient” water heaters just have more and better insulation but the same old resistance heating elements. SInce our water heater is in a heated area any waste heat simply goes into heating the house — a factor which is beneficial in heating season and not so much in summer.
We had also considered a heat pump water heater. They had some at Sears which with all the rebates would have cost very little, but again, where’s the benefit? I would be taking heat from my heated area and using it to heat water then myb furnace would have to make up the loss. Plus I suspect the heat pump unit would need more repairs than a typical resistance electric water heater and at higher cost.
Bottom line is I see little benefit to replacing our old electric water heater.
Can someone show me the errors in my thinking?
Replies
The self-contained heat pump water heaters only really make sense in areas where cooling is required more than heating.
You can buy 2-piece heat pump water heaters, so the heat exchanger is outside, but they're expensive.
Don't fall for a tankless unit -- they're expensive and rarely save money.
You can replace your current unit with a better-insulated one. The Marathon unit is probably the best in this regard, but they're about twice the price of a standard unit. Better to just find the best-insulated conventional unit you can find if and when when it comes time to replace. Save the money you didn't spend there to put down on a heat pump furnace (f you're current heating with resistance heat).
Thanks. We currently heat with a Waterfurnace Geothermal Heat Pump and are very happy with it. ( Not so happy with the lousy 4 Honeywell zone stats that came with it but that's another story). The waterfurnace has a connection to the water heater to supplement our hot water heating. Adding an insulation wrap to the existing WH is a good idea. I would not even consider a tankless system for many reasons I won't go into. Thanks again
Assuming that your geo pump
is currently doing most of the water heating, you're already way ahead. The only things I might add are, do you really need 80 gallons of hot water, and what will happen to the floor if the water heater leaks. If/when you replace the tank, maybe down-size it and make sure the drain pan under it is going to work correctly.
water heater
You got that one right.
recently needed to replace 20 year old HW tank. Had a drain pan. Discovered the leak in the tank just before we went on holiday. Did not want to replace it just then. Saw it dripping into the pan and then into the drain line "We replace the tank when we get back". Came back and discovered the drainpipe in the 2' high crawlspace was not connected to the main drain at all.
What a mess to clean the "lake" out.
Replaced the tank with an A.O.Smith 40 gal Effex model. Tank fully recovers in about 15 min
Main drain... say what??
Hopefully you're not talking about tying your pan drain into the sewer line. It should be piped outside to free air with enough slope to drain easily.
Depends on where you live and whether the heater is above ground.
Your analysis is well-thought-out, and the only thing I would suggest is that you pull the anode rod to see how far it is consumed. If it is more than half gone, replace it. You can protect the tank from rust-through almost indefinitely by replacing the anode rod periodically.
Other parts, like elements and t'stats, can easily be replaced.
You got your head on straight. If the existing heater is working fine ... leave it alone. No economics in changing ... especially when those water hog kids are gone.
When you are FORCED to choose (due to failure of your unit), THEN think hard about your options.
Also ... if you didn't turn down the temp of your water heater when your kids left, you might think about turning it down until you don't get what you want out of it (either right temp of water or you run out of water), then ease it back up a touch ... now you've minimized your heat loss from the tank.
Heat pump water heater dump cold air into the house ... great in the summer ... not so in the winter ... where your furnace needs to compensate.
You're in the NW ... don't go the heat pump route ... it's not as efficient as you might think for your application.
Also think twice about "energy efficient instantaneous water heaters" ... don't buy what you don't need and those are expensive!!! ... and not nec. particularly efficient ... relatively speaking.
keep on making good decisions.
I think you are on the right track. Watts are Watts,but ..... THe big issue people have with storage tank heaters are the stand-by losses. I have pretty big tank and I have let it sit unused for over a month. IT cost about $8 to keep theh water hot for the month or about $100 a year. You get to keep the benefit of about half that amount (heating season) as it just helps heat teh house. SO stand-by loses are about $50. NOW this is a gas hot water heater, so an electric heater in the PNW wuld be about twice that amount.
The heat pump idea is just plain stupid during the heating season for the reverse reason about . You use your furnace to heat the air, your heat pump takes the heat out of the air to heat the water so in effect your furnace heats the water. No savings there. In the summer the heat pump uses natures heated air to heat the water. Hard to do the math and the payback on that one. They are not cheap.
The instant/tankless heater are expensive and I think people have a hard time being happy with them as whole house heaters. Electric is slow! And again, watts is Watts and all you save is stand-by loses. And standby losses can be kept down by keeping your tank size down! Electric resistance heaters are cheap so maybe just getting a 50 gallon tank would save you the most and cost you the least.