Unreasonable Electrical Consumption

[Jadnashua]

20Kw~68K BTU. An electric water heater is nearly 100% efficient, so each of those watts/BTU go into heating the water.

1 BTU will raise one pound of water one degree F. A gallon of water = 8.3#. If you know the incoming water temp, and the outgoing temp from the WH, you can figure out how many gallons it heated, but some of that would be lost in standby...probably not much more than 5% or so, though, in radiational losses. See how that compares to what you think you are using in hot water during a typical day.

 

[WorthFlorida]

....One thing I do wonder about is the hot water recirculation system.

That right there can add a good load because you end up with two pipes of heated water for one faucet and the pipes then radiate the heat into the home. Your saving water at the price of heating the water twice. So when you run one faucet and the pump turns on, do all of the faucet get recirculated water? If so that is like having a pretty good size radiator when heat is not needed. I would turn off the pump for a few months and see what happens.

I did noticed that you have an 80 gal tank and that is a lot for just two people. Most homes are 40 or 50 gal and I have and prefer a 50 gallon. A 40 gallon unit you can occasionally run out of hot water. Therefore, you're heating up to twice the amount of water that most homes do. If you had two 40 gallon water heaters you would wouldn't use that much more in power than you currently consuming. Also, it has a 5500 watt element at 240v's that is really needed for a comfortable recovery rate with a 80 gallon tank.

Water heaters have come up in price lately and if you can DIY replacement yourself it be about $415 just for a 50 gallon electric unit with a 4500w element, 6 year warranty unit. From your other post I think your bill should be at least a 1000 KW less.

Turning off the pump and replacing the water heater will help but if it doesn't cost anything have the electric meter replaced. When yo u talk to the electric company do tell them that the high meter readings is questionable. They sometimes offer a free energy audit.

 

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[Jadnashua]

FWIW, one larger tank will have less surface area to radiate than two tanks half its size. Plus, once the water is heated, it all depends on the amount and quality of the tank's insulation. A larger tank may not use more energy than a similar volume of smaller ones during standby. Newer homes require the hot water pipes to be insulated...it's a good idea to insulate any you have access to. Look at recirculation this way...you want hot water without a major wait. Without recirculation, you might have to wait a minute or more. That may mean you waste at least a couple of gallons of water. That means you will need to reheat 2 gallons or more of water as you purge the pipes of what has cooled off even though you may only need 30-seconds to wash your hands. That means even though you aren't using it, you're throwing away a fair amount of water that you paid for, and paid to heat, but it didn't arrive hot until way into the time you wanted it. IOW, especially if you insulate the pipes, you can save energy and resources that you don't have to pay to treat through your water bill, pump to your house, and then pay to dispose of via the sewer, not counting the waste of resources.

 

[WorthFlorida]

I agree with you but as I stated to save water it may be increasing his power consumption. I do realize that to heat 80 gallons of water with one or two heaters takes the same energy. Only lost is what the tank itself disapates through the insulation and piping. New water heaters to meet the latest energy code are incredibly insulated. It looks like close cell foam, thereby, to reduce his electrical consumption I suggested the two items but it will have more water waste.

 

[SAS]

The problem clearly is the recirculation system. While no two days usage are exactly the same, we used 20 kwh in one day with the recirculation system on for 18.5 of the 24 hours, as I have it on a timer and is only off between midnight and 5:30 am. I just completed a day with the pump off and the valve closed and we only used 2.8 kwh. So the problem clearly is not the hot water heater itself, even though now that there are only 2 of us an 80 gallon unit is larger than we need. That said, when the kids and grandkids visit it's nice that we never run out of hot water.

The question now is: why is the recirculation system losing so much heat and what can I do about it? My wife is very fond of the hot water always being hot, so just leaving the system off is probably not a good answer. Insulating the pipes might help, but in many places they are inaccessible. I guess I should first try to find any that run along outside walls, but without opening walls it won't be easy (or perhaps even possible) to insulate those pipes. I can play with the timer to see how much that helps. I'm also considering a clip on aquastat, but I'll have to replace a section of cpvc with copper to do that. I see that Taco makes a smart outlet that is supposed to monitor usage and automatically adjust, but I'm not sure how well it actually works as I've only seen one fairly detailed review and it was not good. I could try using some of the newer remote switch options, but those require that you first switch the pump on and then wait for it to cycle the hot water through the system. Any other ideas?

Oh, and I haven't given up on the idea of having the meter changed out. I plan to shut off everything but the hot water heater, let it cool, up the temperature and then compare the outside meter to the new meter on the hot water heater.

 

[Jadnashua]

Does your recirculation system have any controls on it? Or, does it run open, all of the time? Most of the engineered systems have a means of stopping the flow once warm water is sensed at the furthest point. Some do it by turning off the pump, some use a thermostatically controlled valve. Also, what size pump are you using for this? Typically, you can use a VERY small pump. I think mine is something like 1/28th HP.

I think I may have asked this before, but are any of your lines insulated and do any of them run through an uninsulated attic or underneath a slab? A properly engineered recirculation system should not be putting that much load on the WH (by radiating from the pipes).

 

[SAS]

The recirculation system is normally open except for 5.5 hours at night when a timer turns it off. I've just added another period of 6 hours during the day when the timer will turn it off. The pump is 1/8 horsepower and there is no insulation., but the piping is cpvc so the heat loss is less than with copper. None of the pipes run through an uninsulated crawl space, attic or slab.

 

[Jadnashua]

An 1/8th HP motor will use about 1Kw in 10 hours all by itself. It does not need to be anywhere near that big. Without insulation on the pipes, they will still radiate energy, even though they may be cpvc. If there's nothing to throttle the flow once hot arrives at the destination, it's a poorly designed system. I'm not saying mine is the best, but I have mine setup to shut the pump off when the water is just warm at the sensing point which provide hot water behind that furthest point (it's under a vanity sink). So, that sink gets immediate warm, and most everywhere else gets hot once the leg from the main is purged...a fairly short distance.

 

[SAS]

The answer seems to be the hot water heater and recirculation system. Based upon the reading from the meter that I installed on the hot water heater, I was able to add timers to both the heater and the recirculation pump. I adjusted the settings to see if I could dramatically reduce electrical consumption, and it appears that I have succeeded. This month I only used 1,152 kwh. While it's true that last month was an estimate and probably somewhat overstated, looking at the history of my usage, I think it's safe to say that I have made a substantial reduction.

11/22/2017 1,152 Actual
10/25/2017 2,489 Estimated
09/22/2017 2,990 Actual
08/24/2017 2,238 Estimated
07/26/2017 3,108 Actual
06/26/2017 2,535 Estimated

Thanks to all for your helpful suggestions and insights.