We had an 100% increase of power consumption last and this year.

It is mostly the night-tariff, which we now consume 27'000 kWh The day-tariff is only around 2'500 kWh.

First we thought this may be due to our new computers, but then the day tariff would need to be high too.

So the only reason could be the electrical heater and water boiler. Both of which are the same for at least the last 10 years, so it kinda doesn't make sense that it went up so much.

So my thought was, could it be that this year for example one rod in the electrical heater corroded which lead to higher resistance => More power draw?

Or do you have any other explanation?


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    Higher resistance would lead to lower power draw because the supplied voltage is constant and \$P=V^2/R\$. Are you setting your thermostat the same this year as last? Have overnight temperatures where you live been the same this year as last year? – The Photon Jan 14 '19 at 18:46
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    Higher resistance is not exactly a cause of high power drain, if any it could be the opposite. A realy high consumption can more or less have only one real cause: heat production. (For hotter climates: and cold production!) Try to experiment with switching devices on and off, preferrably for a whole night, and note the energy consuption. In other words: go fact finding. – Wouter van Ooijen Jan 14 '19 at 18:49
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    Have you acquired any additional residents, such as teen aged girls? Hot water dripping because of a leaky faucet etc. can cause a lot of consumption. – Spehro Pefhany Jan 14 '19 at 18:51
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    Other things to look for: Do you have a sump pump in your basement? A ventilation fan in the attic? Do you have any old windows or doors whose caulking might have failed? Does your electric heater have a fan, and is it still working smoothly? – The Photon Jan 14 '19 at 18:52
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    @ThePhoton The thermostat is still same. Outside temperatures aren't that much diffrent – Tim Jan 14 '19 at 19:00

So my thought was, could it be that this year for example one rod in the electrical heater corroded which lead to higher restistance => More power draw?

No. Higher resistance will reduce current draw. Thought experiment: disconnect the heater completely to create infinite resistance. Will the power consumed increase or decrease?

It's time for an energy audit. You can start by finding your energy meter and taking hourly readings or time how long it takes for the meter in increment by one or ten units. If these are consistent then you can switch off each circuit in turn and measure the change in timing.

Alternately you can get a power analyser with voltage and current probes and take measurements and log data for each load.

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  • Thanks. I've allready tested all devices I can with a wall plug meassurer. They don't seem extra high. Sadly I can't plug my hous eletrical heater into it (Nor plug it out, as it is built into the house. I will try the power reader thing – Tim Jan 14 '19 at 19:05
  • I just read this but higher resistance will reduce the power used with voltage held constant increasing resistance will reduce current flow its basic ohms law. – Ed Beal Jun 14 '19 at 16:55

I find it funny that some think an old electric appliance would cost more, especially after no changes , I would bet your service contract changed. My Mom signed up for one of these programs and her heating bill tripled, we changed the house over to gas except for the clothes dryer, and her kiln, now there bills are much smaller but if she forgets and runs her kiln and dryer at the same time her bills are higher than they were many years ago. I installed a time clock on the kiln about 7 years ago because mom would forget, my step dad asked me to do the same on the dryer but then it died and I piped NG and a vent and he said can we change more to gas because the change cut their electric in half.

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  • No, contract stayed the same. Even if it changed, it would change how much we pay, not how much energy we actually use. – Tim Jan 15 '19 at 7:37

It is a very common occurrence that an old water heater will consume higher energy for a number of possible reasons. A heating element's ceramic coating may be bad, resulting in energy going to ground (earth) inside of the water heater instead of producing heat. The Temperature / Pressure (T/P) relief valve may be leaking, so hot water is just going down the drain without you knowing about it. The heater may be full of sediment so the elements may be essentially insulated from the water, making then highly inefficient so that they end up being on LONGER than necessary to make the same amount of hot water. In that case a reading taken at any given moment would not look unusual, because it's about the length of TIME that they are energized that is showing up as an energy increase.

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    With the info provided I think you are not correct. Power in the form of heat from an element is the same, if it was leaking to ground a standard 30 amp water heater heater would be done in a very short time. I state this because have you ever watched an arc welder? If there was enough leakage the tank would be done in minutes, maybe hours. – Ed Beal Jan 15 '19 at 1:07
  • @EdBeal Correct. But he might be right about the TP valve leaking. A dripping HW faucet would do the same. – Mike Waters Jun 14 '19 at 16:51

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