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Leo B Watkins's avatar

Thank you for this. Couple of comments though.

Existing WH: In addition to the insulating blanket (great idea) for an electric water heater, you may want to consider insulating the water lines with well fitted insulation, particularly the hot water feed line. For longer length, the better. But particularly the 1st 2-4 ft off of the tank.

Still, the insulating blanket may not be applicable to gas water heaters, particularly older designs that are not direct vented, check with manufacturer or plumber before doing. Safety always trumps energy efficiency.

But if you have one of those designs that are so old that they are not direct vented in your home, you probably should look at upgrading anyway.

For not only efficiency's sake, but indoor air quality. Recent studies show that even low grade CO exposure for long term is a health concern, particularly to those who are vulnerable such as the very young or very old.

Consider installing heat traps in the water line if that is an option.

Also, maintain the tank. For all electrical storage tanks, and particularly if you live in an area where hard water is an issue, routinely flushing the tank for sediment and insuring elements are relatively scale free is usually recommended by manufacturers.

If up grading for electric - consider the size of the new storage tank.

A 1 BR apartment can probably get by with a 30-40gal unit. A 2br home or house 40 gal. If your storing 20-40% less water over time, your losses should be in ratio to that.

When you do look at replacement, look for the energy rating of the equipment. Steer clear of those who don't provide it. The terms are confusing (they did a revision on how they are rated a few years back), but for electric - an EF of .95 or better or a UEF of .92 or better should be your goal, and are readily available for the residential market. Also, insist that the unit have preinstalled heat traps.

Also consider natural gas. Long term, with global warming, may not be the best choice; but with current technology is worth considering. Particularly for water heating. And particularly for those already using natural gas, which may be considering an upgrade. The improvements in efficiency when changing from an open vent to a power vent, and particularly to a direct vented system are real and make financial sense. As are the health benefits.

Even more impressive is if you take the plunge and go to a gas tankless water heater. By design, they have no storage, heating the water only when it is called for, so there are no storage losses.

I know global warming is real. But under current conditions, the best power companies out there are using natural gas or nuclear. There are still some using coal.

All of those have their drawbacks. But they all share the base cost of transmission, which results in about 30% loss from power plant to home for the electricity generated. When you do the math, under those conditions - tankless seems like a viable option for the next 10-20 years, which is the typical life of a water heater.

But again, on the older, electric storage systems - insulation blanket and insulating hot water lines. Then maintain it. Quick, easy, and solid payback.

For new construction, pay attention to line length as well. the closer water use areas are to each other, the less length the hot water has to run before getting to where it is wanted. cont.

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Leo B Watkins's avatar

Regarding heat pump water heaters? Beware.

They CAN work, but I've seen them have some bad applications in the past, to where they were installed with the best hopes and intentions, but when used - after a few months they were turned off and the residents just used them as a very expensive standard water heater.

The energy savings are real, with efficiencies well over 2.00. Many builders and renovators rushed to them about 10 years ago when they 1st came out, but they have rushed back since.

As you mention, they need space for their work to work efficiently. Basically what they are is mini heat pumps sitting on top of a water storage tank. But since their primary function is to create heated water, they rarely if ever create colder conditions for the stored water.

Which means they are removing cold from the water and convecting and conducting it to the immediate area.

So the air around them is much cooler, related to the rest of the living area if they are located within the thermal boundary of the home.

And as you mention - water heaters are often in basements. Which are typically the coolest part of the house anyway. So you take the coolest part of the house and make it 5-15 degrees cooler. Mamma is not happy.

If you can design it to where it could be placed next to somewhere you don't mind it being cooler, such as next to the kitchen - it may be a benefit to you - but again - with existing homes the location has already been predetermined. So be careful.

And also, the lesser but often heard complaint is the noise. Again, it is a heat pump, so there is a motor and fan running. I have seen them turned off as much for that reason as for the comfort.

Again, from an efficiency standpoint, they work well. And I'm expectant that the manufacturers and designers are working to improve those concerns. But the concerns are worth considering.

Still, thank you for the column. Informative.

A great resource for builders and home owners for these type of considerations is the Building America Solution Center run by the Dept of Energy. They are continually updating with the latest standards, guides, and information.

https://basc.pnnl.gov/

Best wishes.

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