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Water Heater Timer?

Post in 'The Green Room' started by Mr A, Nov 11, 2013.

  1. Mr A

    Mr A Minister of Fire

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    Any one have experience with a water heater timer? I have an electric water heater, gas is not available at my house. I have been just switching off the breaker to the water heater. I turn it on for an hour, or two when I forget to switch it back off. I turn it on a few hours before bed then switch it off. I have hot morning showers for the next two days with the 50 gallon water heater off, for two people. I'm wondering if I should also shut the water off, so cold water doesn't refill and cool the stored hot water? I'm not sure if it only refills when the power is on or just refills as it is emptied. We have only been doing this for a few weeks, and I failed to note the meter at the start. It's a 5500 watt heater, and electricity is 12 cents a KWH. Also have time of use rates.

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  2. Grisu

    Grisu Minister of Fire

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    What you are doing makes only sense if you have a very poorly insulated water heater. It uses only very little energy for keeping the water at temp; the bulk is going out when fresh cold water comes in after taking a shower etc. For some calculations how little energy you actually save when you turn it off for 8 days straight see here: http://www.leaningpinesoftware.com/hot_water_heater_vacation.shtml It will be even less if anything for just a few hours. As soon as you turn on the breaker the heater will bring up the water to the preset temp pretty much using the same amount of energy it would have used in between.

    If the water temp is consistently too low you may also invite the growth of bacteria: http://www.treehugger.com/green-foo...41779995941&action=collapse_widget&id=1846296

    If you want to save energy for hot water use less and/or get an on-demand hot water heater.
  3. maple1

    maple1 Minister of Fire

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    I wouldn't do that. As Grisu said, stand by losses should be minimal. If you have an older poorly insulated one I'd just get a new one. If you have a decently new one, you can add more insulation. Or plumb in a heat trap. You're not saving much money, if any, and you're wearing out your circuit breaker (they're not designed to be regularly used as on/off switches). And there is absolutely no reason to turn the water off to it - only do that if you need to drain something for maintenance purposes. And then only after temporarily turning the breaker off. If you turn the water off to it, forget to turn the breaker off, and turn a hot water tap on, you can burn out an element in short order.
  4. sesmith

    sesmith Member

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    If you have a day / night meter, with a cheaper night rate, and a large enough water heater to get the family through the day, then this makes sense. Otherwise not. You can pick up a water heater timer in your local big box building store. Wire it in line, and you're good to go. Just make sure it's set to whatever time your electric meter thinks it is.

    Also, shutting inlet water off will only cause no outlet flow. Kind of counterproductive if you want a hot shower. Likewise when the hot water is not running, there will be no cold water flowing into the heater.
    BoilerMan and woodgeek like this.
  5. WES999

    WES999 Minister of Fire

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  6. Mr A

    Mr A Minister of Fire

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    We actually get hot showers for 2 days, do the dishes, and have a tolerable shower the 3rd day. Unless the power company has given me a faulty smart meter, I can't figure why my bill is so high. The refrigerator, the water heater, the stove/oven, light bulbs,TV. we are only home in the evening, and nothing is on while sleeping plus weekends. Very conscious of conserving energy, to save money but somehow the bill is always around 300 KWH. I thought shutting off the water heater might get it down to 200 KWH, but the semi-daily breaker switching would negate any savings, as mentioned, they are not meant to be switched on and off often.
  7. Where2

    Where2 New Member

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    Check out the info at Waterheatertimer.org. My WH runs 3 hours a day, or less.

    If I had to do it over again, I'd get the $10 digital timer (95205) from HF, the $7 double-pole 30A contactor (DP2030B1002) with a 120V coil from PexSupply and a $10 plastic project box from your favorite electronic surplus store.

    As for getting below 300kWh/mo, good luck. If I got below 500kWh/mo, I'd be thrilled (in my all electric house), because ~550kWh is about what I generate each month.
  8. Grisu

    Grisu Minister of Fire

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    We don't have an electric stove or hot water heater, are mostly energy conscious, and use about 200 to 250 kWh per month. Our baseload is 2.5 kWh per day (100 W per hour) that sums up to 75 kWh per month already. The rest are essentially lights, TV, computers, washer, dishwasher and kitchen gadgets. I think you are petty golden with your 300 kWh per month given your higher demand. The average American household uses about 11,000 kWh per year.
  9. woodgeek

    woodgeek Minister of Fire

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    At your low usage, the energy just to heat the water could be a significant part of your total usage. If it bugs you, get a HPWH like a geospring, esp if your existing unit is older and not so efficient. In your climate, it will reduce that part of your usage 60%. CA may have rebates that make it low-cost. AND if you have time of use rates, you can still use a timer to 'charge it' during cheap periods like at night.
  10. maple1

    maple1 Minister of Fire

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    300 kwh/month is pretty low useage, IMO. We're at about double that, and are also careful with lights on & all that stuff.
  11. Mr A

    Mr A Minister of Fire

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    Reading at waterheatertimer.org, they say a water heater runs on average 3 hours per day.
    3 hours a day @ 12¢ per Kwh
    5500 Watt tank = $59.40 per month
    4500 Watt tank = $48.60 per month
    3500 Watt tank = $37.80 per month
    1500 Watt tank = $16.20 per month
    I have no idea for how long per day my water heater actually kicks on. The chart is in line with what I was thinking, if it is only on for an hour a day, it is going to cost me $16.50. I turn it on every other day, sometimes 3 days, so, $8.25, it would seem switching off the water heater will result significant savings. Maybe I should unplug the refrigerator at night also to really add up some savings. I will continue shutting off the breaker to the water heater this month and see what the bill is. Also, can I wire a switch to the water heater to avoid wearing out the breaker?
    Last edited: Nov 12, 2013
  12. semipro

    semipro Minister of Fire

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    I've done the water heater timer. It was really wasn't worth the time or expense because our tanks are well insulated. Your resources are better spent elsewhere.
    If you really want to decrease electricity costs consider things like:
    • Better home air sealing and insulation
    • Minimizing hot water usage (clothes washer, showers, e.g.)
    • More efficient appliances. Replacing a fridge as old as only 8 years old may result in significant savings and quick payoff
    • Use CF or LED lights
    • Dry clothes on a line. Electric driers will make your utility meter spin like a circular saw. They suck conditioned air from inside your house increasing outside air infiltration.
    • More efficient HVAC. Electrical resistance heating is a hog. Go to heat pumps. Consider a mini-split. Use personal heaters where you can instead of central heating.
    • Identify parasitic loads in electronics like satellite receivers etc. and put them on a power strip you can turn off.
    • Use microwaves for cooking when possible rather than electric ranges/stoves/countertop water heaters.
    These probably aren't strange concepts to you or anyone here but it helps to go after the real energy users first and to do the things that payoff more quickly first.
    Last edited: Nov 12, 2013
  13. Grisu

    Grisu Minister of Fire

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    The bulk energy consumption for your water heater will not be those standby losses by keeping the water at temp but the energy needed to get water in the 40ies to 140 F. In essence, you are trying to reduce the maybe 5% power consumption the heater needs to keep the water at 140 F to 4% while ~95% of the energy are going out the faucet when you take a shower, do dishes etc. One gallon of hot water not used will probably save as much energy as switching the heater off at night for a week. What you are trying to do by switching it off every other day is akin to driving your car only every other day but then commuting 100 miles instead of 50. The only fuel you will save is by having one less cold start, saving a few cents at best.

    Similar your fridge: It will simply warm up during the night and then use a lot of electricity in the morning to cool down to temp again. I don't think you will save anything at all by turning it off at night but you may cause premature demise of your refrigerator. Try to open the door less, that will have a bigger impact. I try to get everything out that I need in one swoop and also pile everything that goes back into the fridge first on the counter and then put it back in all at once.

    One place where you may be able to save some more electricity may be your cooking habits. Use lids other than for pan frying, steam vegetables instead of boiling them in a large amount of water, turn off the burners a few minutes before being done (the remaining heat does the rest, same is true for the oven), get an express-water heater if you heat up a lot of hot water (coffee, tea).
  14. maple1

    maple1 Minister of Fire

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    IMO, the only way you will see much savings from turning your water heater off, is if it is for days on end - like if away for vacation for a couple weeks. If the heater will cool down to the ambient temperature of the room, and stay that way for a while, then I'd say it would be worth it. But you can't run numbers like the above to figure anything out. The diifference in a 4500 watt heater & a 1500 watt heater is when it is heating, it will get up to temp 3 times faster - and if run for the same amount of time will generate three times the heat. A 4500 watt heater will not be running the same 3 hours a day as a 1500 watt heater heating the same water - that logic is flawed. You would be better off in adding more insulation to reduce standby losses - but unless your tank is quite old, there shouldn't be much standby loss anyway. Without changing anything in the standby loss area, you will see very negligible net energy consumption gains if you like the water coming out of it to be the same temperature in the end.

    Insulation & heat traps.
  15. firebroad

    firebroad Minister of Fire

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    I just got an electric water heater (40 gal) installed, before that I used the coil in the oil burning boiler. Wanting to run it cheaply, I bought a water heater timer and had my nephew install it the same time he put in the water heater.
    Unfortunately, the instructions were not clear, and he crossed a wire, effectively frying the circuits in the timer. It happened when I was programming it, causing the circuit breaker to slam off with a loud BANG, and smoke was coming out the the timer, so I did not turn the breaker back on until someone could check/remove the timer.
    Because the heater is new, it is really well insulated. 24 hours later, I still had very warm water. I decided not to replace the timer, and have found that my electric bill (.10 kwh) was not that big, about $15 more than before (which was a huge reduction had I been still using oil).
    I spoke to an electrician friend who told me a timer might save me money, as I am only home for 10 hours a day during the week, seven of which are spent sleeping, but with the newer heaters it probably wouldn't be an issue.
    I still throw the breaker switch if I am going to be gone for more than a day.
    So that's my experience with the timer. Check with you electric utility company, they might have a program that will save you some money such as Maryland's Peak Rewards Program.
  16. woodgeek

    woodgeek Minister of Fire

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    Ok, I think this approach to estimating costs is not reliable, and overstates the savings of a timer (no surprise from a place that wants to sell you timers).

    Each gallon of hot water, assuming it needs to be heated by 70°F, will require 70BTU/lb*8lbs/gal = 560 BTU to heat. Since 1 kWh of electrical energy contains 3414 BTUs of energy, each gallon of hot water you use costs 560/3414 = 0.164 kWh, or about $0.02 of electricity.

    First let's estimate your actual usage of water: You say the two of you can get 2 days of usage from a 50 gal tank. Let's say you use 40 gallons in two days, 20 gal a day. This is 600 gal/mo, or about 96 kWh/mo or $12. About of a third of your total elec usage.

    The unknown is how much of this energy usage is due to standby loss in the tank, and how much is required to heat the water you actually use. Given that it is still warmish after 3 days, it sounds like the fraction from standby loss is rather small, maybe 1/3rd or less, which is consistent with insulation levels of tanks made in the last 10 years. So, even if you perfectly insulated the tank, you might save 35 kWh/mo, or $4. And the timer will **do nothing** since the tank will stay warm when the timer is off, the heat will still be leaking out, and you will need to run the heater later to replace what is lost (when you turn it back on to take a shower.

    So, it sounds like you already use so little hot water you can't save much by reducing usage. Standby losses are $4/mo, might knock it in half with a tank blanket, for $2/mo of savings.
  17. Where2

    Where2 New Member

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    Where on that site are they selling timers?

    In the OP's opening statement, he indicated that he has Time-of-Use metering rates. Leaving the breaker ON and letting the WH grab energy any time it chooses to, including during peak rate times can swing this E-bill higher than it would be if he used the same kWh at an off-peak rate time of day. Since his WH keeps water "warm enough" for 2-days without being connected to power, I see no point in having his WH use any energy during peak rates. Thus, a timer does make sense.

    The other benefit using a timer to schedule hot water can do is leave the residual hot water in the tank resting at a lower temperature than it would be if you simply left the WH to mind itself. A lower delta-T° creates a lower energy migration across the insulating barrier around the tank, leading to fewer BTU's lost.

    In my house, I care about BTU's lost from my WH, because they are lost into my air conditioned space where I pay again to pump them outside as waste heat.
  18. woodgeek

    woodgeek Minister of Fire

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    Sure. But other than mentioning time of use rates, the OP keeps asking about runtimes and energy use. So, from the top, a timer won't save the OP energy, but a timer will save money on time of use rates.
  19. Mr A

    Mr A Minister of Fire

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    Well, I got my bill for the last month. Switching the water heater off for 2-3 days at a time raised my usage aby 46 kWh. Still, it makes no sense to me. If it is off, and only runs an hour every other day, how does it use more electricity? I have a smart meter installed. I question it's accuracy. Trying to lower usage and nothing seems to work.
  20. woodgeek

    woodgeek Minister of Fire

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    Unless you have a meter on the heater (difficult with a hardwired setup) it could be a different load, i.e. noise. In my own case, I have found lots of things that malfunctioned and spiked my usage. My favorite....roofers walked on the ducts in my attic, breaking seams in several places. This spiked my heating bill by ~2000 kWh over two months before I figured it out.
  21. Grisu

    Grisu Minister of Fire

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    Just a guess: Once you switch it on again, the water heater senses that it is several degrees below its set temperature. While it may use a lower wattage for maintaining the temp it could use its full wattage for heating up the water when it is too cold. Thereby it "overheats" the water more than by maintaining the temp. That would simply by design to ensure the water stays hot when you are drawing a lot of hot water from the tank at once.

    If you want to save electricity on hot water look at tankless, on-demand heaters or new units that have an integrated heatpump. If your water heater is in a heated space and that heat is cheaper than electricity the latter should save you money. Solar hot water is another option; should work well in your location I guess.
  22. woodgeek

    woodgeek Minister of Fire

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    As for the higher usage, I had the same idea, but it seems unlikely. Maybe the OP (or spouse) is (unconsiously) taking longer showers in the cooler water, and negating gains? Old tanks starting to leak in the jacket can also show higher usage?

    On how to save, I'm gonna disagree. The OPs usage is so low he will never make payback on solar, even in CA. Tankless/on-demand would nix his ability to save with time-of-use timers, and imo have poor payback to begin with (relative to well insulated tanks). A HPWH would make sense if he has a location for it, but again, payback may be long--it would only make sense if he could get a nice fed or CA rebate on it, and get it installed cheap or DIY.

    A time of use timer should save money, hard to say how much without rate info from the OP. If the current tank has 1" of foam or less, a (cheap) blanket is prob worthwhile.
    Last edited: Nov 17, 2013
  23. woodgeek

    woodgeek Minister of Fire

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    Last edited: Nov 17, 2013
  24. Grisu

    Grisu Minister of Fire

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    I talked about saving electricity, not money. Frankly, the OPs usage is so low that he will have a hard time recouping the cost for any new installation. However, the options I mentioned are something to keep in mind when his water heater needs replacement anyway.
    woodgeek likes this.
  25. DBoon

    DBoon Minister of Fire

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    Hi Mr A - I think you can get your usage down to about 300 kWh/mo, but you have to be relentless in purchasing Energy Star appliances, avoiding electric dryer use, and finding vampire loads (there will be a lot of them). Your cable box alone might be consuming 20W/hour...A HPWH will also help - you are in a favorable climate to get the most of these (mine saves me about 100kWh of a previous 200kWh/mo load in the 8 months of the year that I use it exclusively.

    My wife and I are very thrifty. We have an all-electric house, and she cooks and bakes a lot. We are at about 350-400 kWh/mo. If my wife was more "on-board" I might be able to get it lower. But realistically, she is pretty bought in to conservation - it is hard to imagine the pain I would cause trying to eke out the last 50 kWh/mo. The next cooktop I buy is probably an induction cooktop, and that is really the last lever I have to throw at conservation through purchases.

    Your power company may also be estimating your usage and checking the meter only every other month.

    Also, you might be surprised to find the things that other family members do with electricity when you are not around...:) I often find the dehumidifier running even when it is not needed - the wife is convinced it helps even in the depths of winter. A whole house electricity monitoring system (like a TED) might be worthwhile to understand where all the electricity is going. Realistically, the utility meter is likely right, despite all of the conspiracy theories about them floating around on the internet.

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