Hot Water Heater Timers

They might pay more if they see your energy bill is 50% lower than comparable houses in your area. You should get a bigger bang for the buck too. If it's just two of you, do you really need a 50 gal water heater? We have a family of 4 and a 40 gal water heater (with an R11 wrap round it). No dearth of hot water either. We also have it set to 120F. The difference is that ours is gas. I've recently insulated the 6 ft of hot water pipe copper pipe off the tank as well.

 

I am a little surprised at how much folks are spending on hot water since by and large your frugality with energy outstrips mine. I've been averaging about 19 ccF/month (family of four) before insulating pipes or blanketing the water heater. This is with an ~0.6 efficiency factor, non-condensing, natural gas heater about 1 year old. I do my averages in the non-heating seasons when my only use is water heating. I'm heating about 1.4 tanks/day.

I look forward to rechecking this in cooling season again to see if the upgrades are reflected in usage. (The blanket should be nearly independent of usage and I anticipate about 1 ccF per month reduction.)

I looked back at my electrical usage with an electric water heater and it looks like I was running in the neighborhood of 300-350 kWh/month. I can't calculate it directly, only estimate it by comparing my base monthly electric loads in homes before/after and taking a difference.

Back to the concern about timers. My calcs could be wrong, but I show a paltry heat duty at 120 F in the tank at R8 of about 135 Btu/hr vs. 27,000 Btu to heat the water. The tank contents will cool some, but not a lot, maybe 10% of the total duty for heating that water. (Thermosiphon effects probably make this worse than I'm calculating, double it and the effect is still small.) As a result I don't even have to break out the calculus to get a good approximation that the savings are next to nothing...since the average temp is not falling much and therefore the heat loss is not changed appreciably by the timer...and I still have to reheat the water. Note 1: This result is consistent with efficiency factors for electric water heaters.

For a discussion about this see the following page: Ask Mr. Electricity: Saving money on water heating The guy favors electric too much (his fuel costs are higher than mine) and tends to be high on gas install costs, but he reaches the same conclusion about timers. Note 2: If your water heater is newer than 1998, then he says the savings are negligible.

What is the energy use of the timer? I suspect it is about 5 W (same as my noisy sprinkler timer...sounded just like the annoying water heater timer.) Cost of operating this for me would be 5/1000*24*365*0.1 = $4.4/yr. Of course, I leave the noisy sprinkler timer disconnected except when I'm actually running the sprinklers (very rarely.)

Of course, if you are in an area with different rates depending on time of day, then the timer makes great sense to avoid taking a hit in peak hours. And in fact this is where the DOE's recommendation about saving money comes from:

This nicely explains some of the disconnect we have had in this discussion. See EERE Consumer's Guide: Install a Timer and Use Off-Peak Power for Electric Water Heaters They are specifically referring to different rates for heating in peak times.

 

If your water heater loses heat to heated space, then the loss really isn't much of a loss. (assuming that your heat system is about the same efficiency as the water heater). On the other hand, if you water heater is in a unheated space (garage?) then all the heat loss matters. If your water heater is in an Air conditioned space, then any heat loss effectively counts double,,, the energy cost of the lost heat, plus the energy required to cool those BTUs again!

What is way more important than how you time or insulate your water heater, is the basic size. If you can live with 7 gallons, with a 1 hour recovery, then go for it. Few people need multiple 52 gallon units! There is no reason to heat too much water,,, adding to the cumulative loses.

Icarus

 

Agreed for all the reasons stated above.

In addition, it won't save much at all. The surface area of a 40 gallon tank is only going to be slightly less than a 50 gallon tank. The reduction is less than the ratio of the volumes because for vessels of roughly the same proportions the surface area to volume ratio decreases as size increases. Plus the piping/nozzle losses are fixed/independent of tank size.

In the Deep South that is very likely true (having lived there.) It's not just environmental knowlege, but a kneejerk antipathy toward conservation that one must contend with. Ironically, the actual climate is a good one for projects like this.

That's a reasonable concern too. The best way is to state what maintenance is/is not needed. (If you can show zero maintenance over 5 years that would help.) Another factor is that many sales include a 1 year owner's warranty anyway that protects the purchaser from major failures like the AC, furnace, fridge, water heater, etc.

When it comes to resale most won't unless you prepare a fact sheet about the house that spells it out. If you show utility uses before/after and display the differential at today's price (this is the part to put in bold) then you have their attention. Annualize it or even put it on a ten year basis so that they appreciate what it means for them. Most people think of their bills in dollars, not ccF, kgals, or kWh so you have to translate for them. $30/month is nice, $360/year is better, and "$3,600/ten years" grabs attention...enough that people start looking for ways to discount their maintenance concerns. The three numbers all say the same thing, the latter just puts it into perspective.

I've seen owner fact sheets on homes that were really quite helpful at reminding the potential buyer of the strong points of the home. These seemed to be the folks that had it all together with the home fully prepped to make it move-in ready.

 

It depends. One must carefully consider the basis, climate, etc. Heat going into the utility space does me little good even in Winter. Much of it is getting sucked back out as combustion air, transferred to the slab/ground below, some through the wall to the garage, ceiling to garage storage above, etc. Well less than half is getting to the attached living spaces as best I can determine. So I tend to apply a discount factor and look at these sort of things on a seasonal basis as you allude to.

The AC effect is probably not as strong as double because the AC compressor works as a multiplier to transfer the heat outdoors. Jayman might have a better feel for this.

I run into the same issue with CFL's. In Winter CFL's are shifting some load to the furnace compared to incandescents. However, gas is cheaper, and more importantly, light bulbs are usually in places that really don't need to be heated (ceilings.)

I treat this sort of like the old fast food commercial "keeps the hot things hot, and the cold things cold." If you can't get the heating or cooling where it is needed, then there is more waste.

 

The fridge is a lot worse contributor than a hot water heater - or a better contributor, depending on your viewpoint

I read my meters all the time, so I have actual values. For example, July of 2008 I used 2,300 cu ft of natural gas to operate my hot water tank. No heating at all during this period. The gas fireplace with standing pilot light I turn off in late Spring, and light again late Fall

 

I don't see how downgrading to a smaller tank can help save energy. Yes, it takes less energy to bring it up to temp, which can be helpful when used with a timer, but a smaller tank has more surface area in relation to the volume, so it loses heat quicker.

If looks aren't a concern, you don't have to limit yourself to a tank blanket for insulation. Just leave access to the anodes possible.

Instead of heat traps, you can just put an upside down U in the pipe above the inlet and outlet. Insulate it, and that will cut down on conduction and convection losses.

How cold is the water going into the tank? Depending on that and where your heater tank is located, putting in a second tank, preferably uninsulated, before the heater might help by letting the the tap water warm up to room temp.

Likely out of your budget, but just interesting to look into anyways, is a heatpump water heater. The few I found available in the US were add on units to an existing water heater. When I was looking at them, the heat pump and heater cost around the same as an on demand heater. Moving heat around is more efficient than using resistant heaters, and there are some fringe benefits. If the tank is in a humid room like a basement, the hp will dehumidify it, and some models allow duct work to be attached so cold air by product air can be blown in a central air system. The only downside might be reliability and maintance since there are moving parts.

 

so that's roughly 23 therms. That's a helluva lot for a single guy. We use between 7-12 therms/mo during the summer for water heating. Probably double that in the winter because the water coming into the house is wicked cold during the winter.

Comparing two heaters from RHEEM, it looks like you save about $9/year with a 40 gal vs a 50 gal ($411 vs $420) so yeah, it's just about insignificant.

our water heater is indoors so we benefit from the heat loss. We cool with a swamp cooler, so the losses aren't too bad there. We probably have to turn the cooler on a tiny bit earlier in the day on account of it, but then again, probably not. Cloud cover in the summer has vastly larger influence on that (and whether we have the shades drawn or not).

 

Would be nice if thermostats could be set at different temps for different periods during the day. Has anyone patented this idea yet?

 

The point I was making about AC use vs. heat sources such as water heating, CFL's, and refrigerators is that the AC's efficiency ratio/method of removing heat means that the electrical load is a fraction of the original heat load.

With an SEER of 12 this works out to: 1 kWh heat input costs 3.792/12 kWh of AC electrical use. Roughly 1/3 kWh per kWh heat added.

Becoming more electrically efficient is increasing my nat. gas use in Winter compared to what it would be otherwise. This is closer to a 1:1 on a consistent unit basis, but as I've mentioned before, heat added by incandescents is near the ceilings where it does little if any good. As a result I tend to assume the cooling and heating effects cancel one another out on average, although I recognize that there is relative heating/cooling load shifting that should not be forgotten.

 

It is an interesting concept that might get some market play eventually as energy prices get even higher. Lower component costs of ICs and microchips means that at some point one of the hot water heater manufacturers will seize on the idea as a value added feature with little additional cost. I doubt that there is intellectual property opportunity to be had here, though.

Essentially, a timer is a set back device, provided that the off interval is short enough to prevent a complete return to ambient temps. It's net effect is to selectively increase hysteresis in the set point with a bias to lower averages. It is a somewhat clumsy attempt at energy conservation though, considering the energy overhead in running a timer and the load capacity requirements of the switch. Each time power is restored, the HW heater will be in closed circuit mode demanding power. The switch's contacts must be rugged enough to be capable of contacting under load for years of service.

I've got one. It came courtesy of the previous owner of my house. I don't think I would install it, if it wasn't already there for reasons stated above and in other's posts on this thread. Not enough bang for the buck and the hassle.

 

Many older HD electrical timers have good contactors that will withstand years of such service. For example, the ones used for outdoor parking lot lights need to be able to reliably switch 4-8 KW at 208/277 vac

There are a lot of solid state timers now on the market. They reliably perform the same service, but with no contactors to wear out

 

I use my gas water heater timer and save money each month.
THAT'S RIGHT...a gas water heater timer. There is a web site. Type in the www then the gaswaterheatertimer.

 

This is archaic technology. Move to a "hot water on demand" system where water is heated, electrically or by gas, as the water is used. There is no standing storage of hot water. Why throw good money after bad?! This is a Rube Goldberg device tied to use of fossil fuels and totally ignores conservation, efficiency, solar and other renewables.

 

Hot water on demand is also referred to as tankless in a lot of areas. I tried this with a cheaper unit, and it worked pretty well during summer, and OK in the winter. I didn't have a professional size accordingly, but the initial capital expense for this is still pretty high if sized accordingly. For someone whose water heater is < 5 yrs old, there is no real economical reason to spend several hundred $ on this upgrade.

For me to get a properly sized tankless electric unit, it would require 3- 220 lines run to power it. The electric wire itself would run approximately $200-300 due to the length of the run. They also recommend a "quick-disconnect" box to cut the power in an emergency (a must for me, considering my breaker box is in the garage and it's an obstacle course getting through there). The electrician will probably want another $200-300 to do the install of the wires, then you have the plumbing cost (I can do this myself, under $50 for parts), and then the cost of the unit large enough, which was close to $500. For the sake of simplicity, let's assume it's $1000 to get this done for me. Subtract $250 for a new tank water heater, and I've got $750 to re-cover in costs. Given that I saved approx. $20/month in electric costs with the tankless before, I'm going to assume it'll be half that with a properly sized unit, which gets me to a pay-back period of 75 months. Essentially a 6 yr payback period to recoup the upfront capital expense difference.

Do I think it's a bad idea to make this move? Not at all! Is it something I will do within the next year or two? Nope. When the current water heater gets older & less efficient or breaks, I will definitely consider it. Given the relatively small upfront cost, I won't consider the expected time left in the house or "added value" because there really isn't a lot.

Could I do propane? Absolutely. However, given that electricity is cheaper than propane and I don't have any propane or nat gas to my house, I'd have to consider the cost of a tank, lines, etc. Plus, the PV array on my house leans me towards electric.

Ok, that was quite a post I just typed up! Feel free to comment, as I'm always up for learning more information and gaining knowledge!

 

Not only do they make sense from a net BTU point of view, but the new modern gas/propane units can be had with wireless remote controls that allow the user to heat the water only as much as needed. They also work very well for topping up the heat in solar pre-heated water.

The only water heat system (conventional energy) that makes more sense is using waste heat from A/C. This allows the A/C to run more efficiently, and give "free" hot water as a benefit.

My simple, homemade flat plate collector, give our family of two 70% of it's hot water on an annual basis. (150% in the summer, ~30% in the winter in the grey Pac.NW. It feeds a preheat tank, that in turn feeds a demand gas water heater that only needs to heat the difference between the pre-heat temp and the desired temp.

Icarus

Try Rinnain, Takagi, Rheem/Paloma searches as a place to start. I personally have not had too much luck with Bosches.

 

Just installed:


Filling taxes next year for a 30% tax credit. I’m filing both hardware and install.

Next summer,, free air conditioning in the utility room and cheap hot water.

Yes, I will relocate the expansion tank up on the wall at the cold water, 90 degree bend. I’ll put the wire nut splice in a conduit box too.

Bob Wilson