Tankless Water Heaters - A Few More Things to Consider

In last week’s blog post, I discussed the amount of money I might save by having a tankless water heater installed, and I concluded that I would never see a return on my investment.  I received a lot of good feedback from that post, both for and against tankless water heaters.  I thought it would be worth bringing up a few few of these points in another post.

Pros

• You can’t put a price tag on going green.  There’s no dispute about this – tankless water heaters use less energy.  Doing the environmentally responsible thing doesn’t always have a measurable return on investment.  I mentioned this last week, but only briefly.   Not everything we spend money on will give us a return on our investment – we all know that.   After all, what’s the payback period on a sofa?
• Tankless water heaters make sense for a cabin / vacation home.  Traditional water heaters have a ‘vacation’ setting, but I’ve heard it’s a bad idea to use this setting, because it greatly increases the potential for legionella pneumophila growth.   Having a tankless water heater installed in one of these settings would result in much more than a 25% fuel savings.
• Energy Star Tax Credit.  This $300 tax credit which includes tankless water heaters, expires December 31, 2011.   You can read about it here - tax credit.  I’m guessing we’ll see another one show up when this one ends.
• Fuel costs will continue to rise.  As we all know, fuel costs continually increase.  If fuel costs tripled in the next 20 years at a linear rate, a tankless water heater would actually give me a return on my investment, using the numbers from the example last week.

Cons

• Low water flow = no hot water.  If there isn’t enough hot water flow, a tankless water heater just won’t turn on.  One person even commented that they had to turn on the hot water faucet at their bathroom sink and leave it on the entire time they took a shower, or they couldn’t get hot water.  For instance, Rinnai tankless water heaters need at least .6 gallons per minute, Bosch units need .65 gallons per minute, and Rheem at least .4 gallons per minute of hot water flow to kick on.
• The cold water sandwich.  If you think gefilte fish sandwiches sound bad, just try one of these.  The cold water sandwich effect is something that happens with every tankless water heater.  When the faucet is turned on, off, and on again, you’ll end up with a slug of cold water interrupting your hot water flow.  Some tankless water heaters require the call for hot water to last for at least three seconds before the burners turn on, so there can be several layers of hot and cold water in the pipes.  This doesn’t exist with traditional water heaters.  You can read more about this at Rinnai’s web site– they claim to have nearly eliminated the cold water sandwich, but not completely.
• The long wait for hot water.  I already have to wait for approximately forever to get hot water at my kitchen sink, but the wait would be even longer with a tankless water heater.  One interesting solution that I heard a plumber mention was to install a dedicated 3/8″ supply line to his kitchen sink from the water heater.   He claimed that this still provided just as much water flow, and made the wait much shorter.  I’ve considered doing this at my own house, although this is technically a code violation.

For me, a tankless water heater doesn’t make sense just yet.  I’m waiting for the price gap between tankless water heaters and standard water heaters to get a little smaller.  I have the temperature cranked up on my water heater with a tempering valve installed, so I never run out of hot water.  Maybe by the time my kids are teenagers I’ll have a different opinion of tankless water heaters.

Reuben Saltzman, Structure Tech Home Inspections - Email - Home Inspector Minneapolis

    

My Beef With Tankless Water Heaters

Tankless water heaters are sexy.  They take up less floor space, they provide an endless flow of hot water, they’re environmentally conscious… and they’re really expensive.   If you enjoy showing off your home’s mechanical equipment to your friends or you’re in to being green at any cost, get a tankless water heater. On the other hand, if you’re in to saving dough, doughn’t buy a tankless water heater.

A tankless water heater will not save you money.

I stopped by my local big orange box the other day to check up on the latest sales pitch for tankless water heaters.  The brochure for tankless water heaters said they can save up to 25% in fuel costs.  That sounds great, but lets examine what that means. I spend about $12 per month for natural gas during the non-heating season, if I don’t include my fixed fuel costs, such as the ‘fuel delivery charge.’  This figure includes the gas for my water heater, clothes dryer, and oven.  Just for the sake of argument, lets also pretend that I don’t have a family of four who uses the clothes dryer all the time, and I don’t use the oven all the time.  We’ll pretend that I spend the full $12 / month just  to keep a 50 gallon tank of water hot all the time.

Fuel savings

If I save 25%, I’ll save $3/month, or $36/year, or $720 over a period of 20 years.  My standard 50 gallon water heater has a 12 year warranty, and so does the tankless water heater I looked at… but the life expectancy for a tankless water heater is apparently 20 years, so I’ll give it the benefit of the doubt and assume it will last that long.

Sizing a tankless water heater

The brochure on tankless water heaters said I should buy the largest tankless water heater they make, based on the number of bathrooms I have in my house – three.   The particular model is the ECOH200DVN.  This unit boasts a 9.5 gallon per minute flow rate at a 35 degree rise in temperature.  With an average ground water temperature of 45 degrees here in Minnesota, that would give me… 80 degree water.  Ha!  That’s useless.  To get 120 degree water, my flow rate would be reduced to 5.1 gallons per minute.  Maybe I’ll need two water heaters. For the sake of argument, lets just say I only need one.  This unit retails at my local Home Depot for $1,427.00.

Installation costs

Plumbers charge a lot more money to install tankless water heaters, because they’re a lot more work compared to traditional storage tank water heaters.  The water supply pipes will need to be re-routed, the venting will need to be completely redone, the unit will need to be mounted on a wall, an electrical outlet may need to be added, and the gas pipe may need to be re-done.  Just for fun, let’s say you were able to find a plumber to do all of this for $1,000.   A traditional water heater might cost up to $500 in labor for replacement, so we’ll assume you’re only spending an extra $500 in labor for a tankless water heater.

The bottom line

A traditional 50 gallon water heater with a 12 year warranty retails for $559 at my local Home Depot.   I would spend an extra $868 to buy a tankless water heater, and at least an extra $500 in installation costs, making this unit cost at least $1,368 more than a traditional water heater.  I would spend at least $1,368 for the potential of saving $720 over a period of 20 years.  If I ever buy a tankless water heater, I won’t be doing it because I’m hoping to save money.

Related links:

• A White Paper from A.O. Smith – What’s the Big Deal About Tankless Water Heaters?
• Consumer Reports – They’re efficient but not necessarily economical
• Jay’s Blog - The Fabled Tankless Water Heater

Reuben Saltzman, Structure Tech Home Inspections- Email - Minneapolis Home Inspector

    

Only a 100 amp electric service? Is that enough?

Will your home inspector tell you if your electric service is too small?

While it goes beyond the scope of a home inspection to perform load calculations, occasionally I’ll do a rough calculation if I get concerned that an electric service is too small for a house.  If the service size from my rough calculation comes up too close to the actual service size, I’ll recommend having an electrician perform an official load calculation… and I think I’ve done this twice.  Ever.

At nearly every home inspection, I find one of two things:  either the electric service is outdated and obviously too small, such as the 30 amp service pictured at right, or the service has been upgraded or over-sized and is plenty large enough for the home.  I don’t find much in-between those two.

I got to thinking about this while inspecting a 3,600 sf house in Plymouth for an old friend from high school.  This home had a 100 amp electric service, which seemed too small for that size of a house.  I considered recommending an electrician to do a load calculation on the house, but I first plugged in a few numbers at an online load calculator - http://www.electricalknowledge.com/SFDLoadCalc.asp .

I didn’t have all of the exact numbers that I needed, so I guessed on a bunch of them, such as the VA ratings on the garage door openers, garbage disposer, dishwasher, and microwave.  I put in 1800 VA for each one of these, which is certainly way too high, but it makes me feel better about guessing – at least I’m not guessing on the low side.

This home was heated with a gas furnace, had a gas clothes dryer, a gas water heater, and a gas oven.  The only major 240 volt appliance at this home was the air conditioner.  This is pretty common for a home in Minnesota.

Can you guess what the calculated service size was?  68 Amps.

Granted, my calculation probably wasn’t perfect, and I’m not sure that this online load calculator was completely accurate, but this was enough to make me not worry about the service size.  When I took an electrical inspection class many years ago, we had to perform a lot of load calculations for fictional houses, and I learned enough to know that if most of the major appliances are gas, a 100 amp service is probably plenty enough.

I invite you to plug in the numbers from your own home at the online load calculator that I linked to above – you might be surprised at how small of a service you could actually get away with.  For the record though, the smallest allowable service for a new home today is 100 amps.

Reuben Saltzman, Structure Tech Home Inspections - Email - Plymouth Home Inspector

    

Is your water heater large enough for your bathtub?

You’re all set to try out your new whirlpool.  You’ve lit your candles, you’re turned on some Enya, you’ve poured yourself a glass of wine, youcleaned the gunk out of the jets last week, and you’ve filled your tub with hot water… oh wait.  Your tub is only halfway full, and you’re out of hot water.  Bad times.  This will happen if the water heater isn’t large enough for the bathtub.

Determining if a water heater is large enough for a bathtub is actually pretty simple; the water heater tank should be about 2/3 the size of the bathtub.  For example, if you have a 40 gallon water heater, it would be just large enough for a 60 gallon bathtub.   A very small bathtub might hold 40 gallons, while a larger single person bathtub could easily hold 100 gallons or more.

My bath tub holds 110 gallons (pictured above), and my 50 gallon water heater couldn’t even fill it with enough hot water to use the whirlpool jets.  That’s how my house was built, back in 1998.  Can you believe it?  For a bathtub this size, a 75 gallon water heater would have been about right.

In order to use the whirlpool at my bathtub, I cranked up the temperature on my water heater from a safe 120 degrees to a dangerous 140 degrees (or so).  With 140 degree water coming out of the hot water spout at my bathtub, I could mix in a lot of cold water to get the water to a comfortable temperature, and I was able to fill up my bathtub.

That’s nice for me, but what about my three-year-old son?  This wasn’t safe at all – at 140 degrees, it only takes a few seconds to get 2nd or 3rd degree burns.

To make up for this, I installed a tempering valve at the hot and cold water pipes right above my water heater.  Now, cold water gets mixed in with all of the hot water coming out of the water heater, making it seem as though my water heater is much larger than it is.  The water that comes out of the faucets can be adjusted at the tempering valve, and I have it set at 120 degrees.  This was a much cheaper alternative to replacing my water heater or buying a second water heater, and it was fairly easy to install.

Done and done.

Reuben Saltzman, Structure Tech Home Inspections - Email - Home Inspector Minneapolis