Help! Very high electricity bill after solar panel installation

shanibhJanuary 11, 2009

I appreciate any help with this VERY frustrating problem.

I have a two-flat in the Chicago area. During recent gut rehub of the building I had 5 panels of 4' x 10' AFT Solar Collectors for a 120 galon solar storage tank. According to my contract, the system also has 5 Grundfos solar circulating pumps. The system was designed to assist with the furnace heating system and hot water.

My problem is that my electrical bill have gone up from about $30 a month in previous years during the winter, to $180-$200 in the past very cold Chicago months. In the past, my electrical bill was high in the summer, when I used air conditions, but very low in the winter, when no air conditioning was used. My only explanation for the high electrical bill during the winter in the solar system, which, if true, defeats the purpose of the solar. Ouch! Any suggestions or inforation on what I should do would be VERY helpful.

Thanks much for any information or help in what I can do...

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don't go by the dollar amount of the bill, look at the actual KWH usage for the times. if you heat with gas/oil, and now use electricity to help circulate the water, then it is natural for the bill to go up SOME. though i do agree that your bill seems a little excessive. is it possible that you are on avg billing and the construction caused your usage to go up while they were working and the POCO is just now billing you the difference?

or could they have misread your meter for someone else's? get your bill and read you meter yourself to verify the numbers.

    Bookmark   January 11, 2009 at 11:03AM
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The circulating pumps typically draw 80 watts each more or less. If you ran all 5 of them 24/7, it would add 10KWH per day or 300 KWH per month. At the typical rate of 10 cents a KWH, thats "only" $30, and its unlikely they run all the time.

It seems like you need to do some monitoring of the system to find out whats going on. Maybe some other electrical load has been added that you are unaware of?


    Bookmark   January 11, 2009 at 11:32AM
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Thanks much to both of you! I truly appreciate the help. I called ComEd and they will check the meter in their next meter readings (the bills were for actual reads). I also contacted the solar company to have them check.

I checked the bills again and it looks like the kwh usage went up dramatically after the solar installation (300-500 kwh before the turning on the system, to 1200-1600 after turning on the system. All actual readings). Could it be a problem with the installation or acquipment?

Thanks again!

    Bookmark   January 12, 2009 at 5:24PM
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Since this is a Âgut rehubÂ, I would suggest that you turn everything ÂOff in your Âflat and see if your meter is still spinningÂ


    Bookmark   January 13, 2009 at 12:15AM
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I know this is old, but I've had something similar and doing a search brought me here. If I'm correct the solar piping going in/out of your tank goes straight up once leaving the tank and your tank has electric backup and it sounds like you have a wrap around heat exchanger (which this issue is most prevelant in) but others experience it as well.

What's likely happening is at night the cold solar fluid is entering the bottom of your tank, getting heated by the heat exchanger and rising to your solar panels where it's getting cooled and flowing back down the other side of your piping to re-enter the bottom of your tank to repeat the process cooling your tank down at night and causing the backup heating element to stay on constantly.

To fix, your solar piping leaving your tank needs to go straight down ASAP for at least 18" and THEN turn and go up to your panels. This plumbing configuration known as a heat trap is likely your missing piece causing reverse thermosiphoning at night and excessive electric use.

Okay lets see if I can explain why a simple change to the piping will likely make all the difference. Hot fluid is boyuant and floats/rises while cold fluid is heavy and sinks. Hot fluid can't naturally float down, and likewise cold heavy fluid can't naturally sink upwards. By having the solar plumbing drop 18"+ exiting your tank the hot fluid needs to immediately float downward to get to your panels and as mentioned hot fluid can't float down naturally so it gets trapped (why it's called heat trap). Likewise, on the cold side the heavy cold fluid has to sink upwards to enter the bottom of your tank and cold fluid can't sink upward!

There's check valves on your system to stop this from happening, but in many cases particularly with wrap around heat exchangers I've found for them to work properly you have to install the piping backwards to your tank (your tank has a solar in & solar out. For a check valve to stop reverse thermosiphoning you'd have to install the piping the opposite way which reduces your efficiency).

So get your plumber to redo the plumbing by making it go down 18"+ before entering the tank on both the hot & cold solar tank inputs. If one of the inputs is right at the floor then the piping needs to have two 18" dips making it look like long "W". At a minimum, do it at least on the hot side which should be higher.

Just a warning, there are plumbing devices called die-electric heat traps. You can't use them. They are noisy, they aren't designed to handle the temps of a solar loop, and have plastic marbles whose boyauncy when used in regular water lines works however your solar loop has glycol or some mixture of it so that throws their boyancy balance out when used in a solar loop. The heat trap has to be done through a pipe configuration.

    Bookmark   March 10, 2009 at 11:50AM
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Also, the issue could be the sensor is in the wrong place. Especially tanks with wrap around heat exchangers, it needs to be taped to the surface of the brass bolt of the tank specifically for sensors (or replace the bolt with one that's got the sensor in it).

That is the only accurate place the sensor can go that will be the closest match to the water temp inside. If you attached it to the metal of the inside tank (near the brass nut there's room) the metal of the tank is insulated by the glass lining and I've found it can give temp readings around 95F while the brass nut itself is 130F. The metal of the inside tank is not a good location.

If you attached it to the solar pipe right as it exits the tank & super insulate it, that's even worse. You can get temps of 50F even though the water inside the tank is 120F+ there, and on cloudy days and too early in the morning it trick your system to kick on cooling your tank.

I would start with the simple things, make sure the sensor that tells you tank temps is on the brass bolt of the tank made for a sensor and not against the inside metal of the glass lined tank or on the exit pipe of the solar loop leaving the tank.


    Bookmark   March 16, 2009 at 11:42AM
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You know, I have a similar problem.
I have my kWh usage tracked since 2004. In 2005 I had a house fire, and in the next year, we replaced the roof and had a solar, evacuated tube water system put in and 32 BP flat panels installed in the roof. As a matter of fact, I'm the very first, registered residential solar power plant in the state of Maryland I have such a huge system.

In the subsequent years, life has kicked me in the butt. Until this last summer, I lived with no kitchen, no sofits to block wind under my porch, holes in the ceiling where my lights should be, Tyvek paper instead of windows, etc. I've lived in 1 room with my cats and dogs and 6 space heaters.

This last winter was the 1st in 3 where I have had my windows installed, drywall hung, some electricity (rather than extension cords run off the control panel), kitchen appliances, etc.

My power bills have soared, which doesn't make any sense. Checking my kWh usage, which with a more enclosed and insulated house, the kWh should have gone down. I have also replaced my 6, normal blowing space heaters with 2 efficient quartz heaters, too, so even that's better.

We did NOT have the cold winter here in MD that the power companies keep telling us we did. That's total bull, I'm here to tell you.

It almost looks like when they "adjusted" my meter for net metering, that my appliances are pulling directly from BG&E vs. the solar generated electricity being used first. My actual appliance usage is less, since I booted my energy-hog husband, so something's funky, which I, BG&E and my solar company can't figure out. Not that they're trying, but rather blaming each other, but somehow? I see absolutely no benefit to me having spent almost $50K on solar energy.

There you have it.

    Bookmark   April 8, 2009 at 11:18AM
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Interesting choices made

Choosing a solar system before a kitchen, lights, windows, drywall.....

    Bookmark   April 13, 2009 at 6:31PM
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You said your circ pumps are solar and they do not work if their is no sun. If you are having snow and very little sun out the solar hot water system will not work Remember the solar system needs to be free of snow so any sun can hit it. But no sun means no free heat. You might want to get a gas hot water heater as a back up to use as a close recirc system for the heat

    Bookmark   April 14, 2009 at 10:29AM
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Interesting choice, yes, but we had that money and I knew we'd never have it again. So the roof and solar systems. The other stuff, with my husband a general contractor, would come.

Interestingly enough, I saved more before I was able to officially net meter. Even with the sieve that was my house.

    Bookmark   April 15, 2009 at 9:07AM
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Hubby a contractor?

You do know the old story, the shoemakers family has no shoes?

    Bookmark   April 20, 2009 at 9:26AM
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Do I know the story?
You're asking someone who has waited 4 years for heat and air conditioning. My windows took 3 years. I have unfinished drywall up (after 2 years), and finally have 3rd hand kitchen cabinets and water in the kitchen. The appliances, which I found on Craig's, were put in last summer and I can now cook something other than microwaved mashed potatoes.

That's why I took what I could get when he felt like doing it. Solar came first, thank god.


    Bookmark   May 21, 2009 at 3:25PM
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