Hot Water Heaters: When Energy Efficiency Fights Demand Response

[kristopher]

Hot Water Heaters: When Energy Efficiency Fights Demand Response
Out of the basement and into the fire

KATHERINE TWEED: MAY 15, 2013


The home hot water heater is hardly the cool kid in the appliance schoolyard. It doesn't receive daily human interaction. It mostly dwells in the basement. There is no former Apple designer bringing us a new, sexy water heater.

But that doesn't mean the appliance is completely forgotten. There is a tussle brewing in Washington over the second-largest energy hog in the house. The lowly hot water heater has long been part of load control programs run by electric utilities. Some hot water heaters also receive significant rebates as part of utility energy-efficiency programs. Now the two programs are potentially pitted against each other because of proposed energy conservation standards for residential hot water heaters put forth by the U.S. Department of Energy.

Demand response and energy efficiency are often seen as two peas in a pod. While efficiency can drive down overall energy use, even more kilowatts can be shed when the grid needs it most.

The point of contention is that large water heaters, over 55 gallons, will be required to have an energy factor of at least 2.057, a figure that’s double the efficiency of a high-efficiency electric storage heater. The new standard could only be met with heat-pump water heaters, instead of the classic electric resistance water heaters.

The problem is that heat-pump water heaters, while far more efficient, are essentially no good for demand response...

http://www.greentechmedia.com/articles/read/hot-water-heaters-when-energy-efficiency-fights-demand-response

[rickford66]

1. tankless water heater

We've had tankless water heaters for over 30 years. We never run out of hot water. No energy is wasted if there's a drip. No energy is used if water isn't being drawn. The downsides are .... Flushing a toilet while someone is in the shower is a no-no. More flow means lower temperature and less flow means higher temperature, so it takes some getting used to. You have to use low flow shower heads, but it also saves you water. We have electric, but I understand the gas (natural or propane) are better. You better not have hard water or at least get a softener otherwise it will clog your pipes. Ours did but after installing a softener the pipes slowly cleared up. The manufacturers suggest putting two in series or parallel. Don't do it. In series the second one will burn out. In parallel they alternately turn on and off because it's impossible to get exactly the same flow rate to both. The SCR and thermister that controls the heating current can be readily replaced if need be. They last about 10 years without trouble, about the same as a full tank heater in hard water country. The ones I've bought were manufactured in Europe but bought locally. When I've been in France for work I investigated buying one there but it was actually cheaper here.

[FBaggins]

5. The new ones have improved significantly since then

Had ours for a couple years now. No trouble with toilets or other cold water demand. It can handle two (full-flow) showers and a sink/dishwasher at the same time (depending on input water temps) before the pressure and temperature start to drop. Ours is outside, so it doesn't even take up closet space. Hard water is an issue, but it's plumbed to easily pump vinegar through it once every year or so - so that's no problem. And it's expected to last 20+ years.

[rickford66]

6. more info please

Is it gas or electric ? What's the brand name ? Space isn't a problem for us. It's in the basement and is smaller than a shoe box.

[FBaggins]

7. Natural gas

Though many similar models will just as easily run on propane. It would be tough to find an electric unit with that much capacity (essentially 200,000 btu)

Space (or future space if you finish the basement) isn't the only advantage of an exterior unit. Each installation has its own challenges (sometimes making tankless a mistake), but venting costs and expenses for running new gas lines can be anywhere from negligible to thousands of dollars. In some situations (ours), the exterior unit is a much cheaper option.

[rickford66]

11. this should be helpful to many others

We chose electric for several reasons. For an allergy free home we have no gas appliances. Gas is more dangerous than electric (I know I'll get hammered for that, but that's our experience and being an electrical engineer and having been an electrician, I feel more comfortable with electric). Exterior propane tanks have been target practice for nitwits in some rural areas. Natural gas would be out of the question anyway as we're at least 10 miles from any source. Exterior units would be impractical here in upstate NY. We're used to our electric unit but many others would be very interested in the gas unit you have. Who is the manufacturer? How much do they cost?
Electric units are much more limited than gas units so we have to weigh the pros and cons of each. Thanks.

[FBaggins]

14. Mine is a Rinnai

Sorry that I left that off.

How much do they cost?

There's a large range. This unit (~200k btu and upgraded electronics) retails in the $1500-$2,000 range - though I found one for about half that much. So about double what a quality standard HWH would cost (but they are expected to last at least twice as long and have much lower costs to operate).

The real challenge comes on installation. I've read of people who had to spend thousands more - because they had to upgrade their gas service/meter and change their venting. It can get very complicated.

In our case, the unit is right next to the incoming supply and it was already big enough (two oversized furnaces and an existing gas HWH along with a planned gas-log fireplace and cooktop - meant that we had capacity to spare) and it was just the other side of the wall that used to have the HWH on it (so little extra plumbing was needed) and no venting. We lucked out because it was the first exterior model that the local gas company had installed (and right after they were trained), so they broght a number of crews out and worked on it all day long... then wrote it off to their training budget. It was a pleasant surprise to learn (after they finished) that all we had to pay was the cost of ingredients for the fresh lemonade and cookies that my kids made for them.

[rickford66]

15. You made out OK

For a propane model a homeowner could install it themselves. Good luck with it. Every bit of energy saved is a benefit.

[bobja]

2. Why heat hot water? n/t

[CRH]

3. Actually, my hot water is on my roof, heated by the sun, ...

and more efficient than any grid system I have ever had. There are alternatives for those so inclined. Alternatives that pay for themselves, in less than a third of the lifetime, of the system. If you get an average of five hours of sun a day, you are in the mix, and it becomes a matter of choice, of how you spend/invest, your money. A new car, a wide screen TV, or a water system. Only one of the above pays for itself in a third of its useful existence, only one of the above rewards your perceived pleasure.

[trof]

13. Same here. Love it.

[Mango Suede]

4. Solar-heated hot water - loving it !

We live in Maine - up here in the northeast corner of New England - and for two months now we've been heating our hot water with a 30-tube solar array. In late April, when temps were in the 30s and 40s (daytime), the tubes averaged 180-190 degrees. We've had a cloudy, wet spell since, but the tank is equipped with an electric element for cloudy/winter/nighttime heating. No more paying close to $4.00 a gallon for #2 oil. And with the tax incentives we received, the system should pay for itself in six years.

[Socialistlemur]

8. I use a natural gas fired heater

Our water heater is heated using natural gas. It has a tiny tank, but it has the ability to heat water in large quantities when the water is needed. The only issue is the need to wait for about two minutes to get hot water. I'm amazed when I read the way it's done in the USA, it seems to be so I efficient. What you need is natural gas heaters, gas prices in the USA are very low.

[FBaggins]

9. Not all gas prices are so low

Many of the consumer pricing plans have seen only modest improvements. The big declines have been for large users.

So much so that when I just installed a new hvac system I went dual-fuel and will only use the gas furnace when it's below somewhere in the 35-40 degree range.

[Socialistlemur]

12. I guess you have cheap electricity

It's something you have to study. The dual fuel comes in handy if you get a power cut if the controls run without electricity. I had a house with natural gas fired heaters, the power went out and we couldn't heat. Lucky for us we fired the gas stove and stayed alive in the kitchen. But you need a monoxide alarm too just in case.

[Kolesar]

10. Apparently, they are less-useful for load shifting because the heat-pump types use less current

Did I read that right?