my brother and I recently started a project to build a patio over a jacuzzi to protect it from snow, and this requires drilling holes in concrete for anchor bolts for the posts. After we started, the next electric bill he received was around 600% increase (from 120 to 800), and 12 days since, the bill is already higher than before. We did not see any wires into the concrete but we fear that there was a hidden cable that is now damaged and draining electricity with no access anywhere. We have no idea what other cause of the electric sprike could be other than maybe a rat or rodent chewing a main wire somewhere.

Edit: Additional information: The avg KWh per month is around 550, spiked usage month is 2700, current usage 12 days in the cycle is over 3000.

Used a rotary hammer drill to drill about 6 inches into the concrete. Then we filled the hole with a very strong concrete glue before putting the 4 inch anchor bolts down as flush as possible.

Jacuzzi was only turned on once to check if it could be used when he bought the house, but never turned on since. HVAC system was turned off when we left the house, and we only worked on the weekends, so about 4 days in total so far.

EDIT 2: ISSUE FOUND So we found the issue, it was two switches in the garage that turn on nothing in the house, but the house was using 6 KWH/ hr and after switching it off, it went to less than 1 KWH/ hr. These switches turn on two small boxes that seem to only heat up a lot (hot to the touch) but does nothing else. Have no idea what they are for. Can someone explain what this thing is for?.

Switches with boxes

Edit 3: Opened boxes enter image description here

Sorry for slow update. After finding the cause, we went straight to work on the patio and didn't check the thread till after I left. My brother opened the box for you guys here. Appears to be a bunch of heavy duty cables for high voltage. Still not sure where this even goes though, so we are probably going to box off the two switches and change them to smart switches so we can remotely monitor and turn them off if they ever turn on again. I would love to investigate what these are for in the future in another post.

Thank you everyone for your advice, it helped a lot in isolating the issue and finding the cause.

  • 10
    I think the question about "what is this thing?" should be a separate question by itself Commented Oct 17, 2022 at 12:16
  • 1
    One wonders if those cables don't feed a heater somewhere.
    – Hot Licks
    Commented Oct 17, 2022 at 18:05
  • 3
    Heated driveway is my guess. If so you won't find any "device" or the other end of those cables anywhere. But your driveway will be warm. The boxes shouldn't be warm ... that also could be another question. And most smart switches don't support this much current so watch what you buy.
    – jay613
    Commented Oct 17, 2022 at 18:14
  • 1
    @Tai What's the climate where this house is located? You can't see them, because they got moved to chat, but several comments speculated that those "heavy duty cables" might lead to electric heating elements underneath a sidewalk or driveway, designed to keep them clear of ice in the wintertime. Commented Oct 17, 2022 at 18:15
  • 1
    @SteveSummit The house is in a mountain range with snow and ice, so I do believe that it is possible they could be for snow melters as mentioned in other comments.
    – Tai
    Commented Oct 18, 2022 at 7:25

5 Answers 5


Many electric utilities provide online access to usage data at the daily (nearly useless for this type of problem), hourly or 15-minute (that's the industry standard) level. If you can get hourly or 15-minute data, that should provide some insight, at a minimum telling you if this is a constant problem vs. specific times of day.

Electricity doesn't "leak" in the way that water does. In particular, electricity always runs in complete circles. A hot wire exposed to the air does nothing unless/until there is a path back to neutral and/or ground. Note that the physical ground (dirt) is a very poor conductor, so a bare hot wire stuck in the ground will be extremely dangerous but not likely use up a lot of power. On the other hand an actual short circuit (which is common enough when doing renovations without full knowledge of the wiring setup) will trip a breaker, so that won't explain high usage either.

As others have suggested, working circuit by circuit (breaker by breaker) to narrow down the spike is often the only way to find the source of the problem.


From data you just gave, previous usage was 90 KWH/day and have leapt to 250 KWH/day, so 140 KWH/day unexplained. That is 6 KWH per hour, or more simply 6 KW. And this is the AVERAGE. OK, so what is 6KW?

  • 20,000 BTU/hour of heat, enough to electrically heat a large home (noting it's continuous, not max rating).
  • 25 amps at 240V (range maxed out, or 2 water heaters cycled on)
  • 50 amps at 120V (six space heaters running full blast)

Continuously, or average. That is, it might be 5 times this much 1/5 of the time, but that would be insane.

Can't possibly be a nail through a cable!

Absolutely not. That nail would be emitting 20,000 BTUs from a thing the size of a nail, which is hot enough to initiate nuclear fusion. You would have noticed.

The season has changed. Could it be heating load?

Yes, in one of two scenarios.

First, does the house have electric resistive heating and this is your relative's first winter in the house? Because if they are not accustomed to the cost of resistive heating, it might catch them by surprise.

Second, does the house use a heat pump (reversible A/C) for heating? Now October is perfect heat pump season, and the heat pump should be heating the house very efficiently. If something has gone wrong with the heat pump, or if the thermostat is not properly configured e.g. because someone installed a Nest this summer and never tried it during heating season..... here's the problem.

Heat pumps are often installed with a system called "Emergency Heat" of resistive heating. It "fails over" to that if the heat pump is inoperative or configured incorrectly. So it might have an efficient heat pump that is not working right now.

Did the electric rate tariff change?

Another blind-side is electric tariffs (pricing schedules) from the power company. There are many tariffs out there, and some of them have gotchas in them that will explode your wallet if you don't know about them. So take a hard look at the electric bills, and see if your electric usage in KWH hasn't changed but the price has.

  • A lot to digest there. As far as I know, there were no changes to the prices, and they charge 19.5 cents per KWH. The usage last month was 2700 KWH and the current usage after 12 days is over 3000 KWH. There may not be an nail, but maybe the anchor bolts is touching the cable ground and live wire, if there is a hidden cable. Also, the HVAC system was turned off before we left the house two weeks ago. Idk if the system could turn on itself again.
    – Tai
    Commented Oct 14, 2022 at 21:53
  • 16
    @Tai doesn't matter whether a nail or anchor bolt has reached the temperature of the surface of the sun. You would notice LOL. Rest assured no wire fault of any kind is absorbing 6000W on average without having burned the house down. It is something else. Commented Oct 15, 2022 at 0:06
  • That definitely reassuring to hear, but now I have to figure the true issue with the spike in power usage. And I have no clue. I can't investigate until two days later, I'll update the post on my findings.
    – Tai
    Commented Oct 15, 2022 at 0:19
  • 5
    A $12 clamp meter will pay for itself before bed time on the day you buy it :)
    – jay613
    Commented Oct 15, 2022 at 15:03
  • @Harper-ReinstateMonica what tariff are you using and from where? Seems very low. Very very. The logic and conclusions hold regardless but still I'm curious. ($120 for 90kWh/d = 4 cents? Mine's 17.)
    – jay613
    Commented Oct 15, 2022 at 15:57

Electricity doesn't just "leak" out like water would. It needs to complete a circuit, and if a buried underground cable was leaking that much to ground, I'd expect you'd be tripping a breaker somewhere pretty quickly.

What were you using to drill the holes into the concrete? One of those rental rotary hammer drills draws a fair amount of juice - some are around 1000W. That, combined w/other power tools, maybe higher A/C usage because of you going in and out more often during construction, they could all add up.

Also, look at your power usage on the bill, not just dollar amount. Most utilities charge "tiered" rates and when you pass a certain threshold the rate per kWh jumps up, making the dollar amount go up much faster than the actual usage suggests.

  • 1
    Large breakers (as for a hot tub heater) can support quite lot of "leak" before tripping. I heard and watched my oven element turn into a volcano when it failed. The 50A breaker never tripped. Fortunately I was there to turn off the oven manually.
    – Ecnerwal
    Commented Oct 14, 2022 at 19:02
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    We only used the rotary hammer drill on the first day and should not be reflected in the nextonths bill that is already higher than last months bill. The other power tools were battery powered.
    – Tai
    Commented Oct 14, 2022 at 19:05
  • What's the weather like and what is his heat source? I'm assuming that since you're building a roof to keep snow out that it's getting colder there. I'm also assuming this is a fairly new home to him? Most likely answer is additional use from construction plus weather-driven changes in usage.
    – Chris O
    Commented Oct 14, 2022 at 19:08
  • The weather is getting colder but it is still within range of the set temperature to maintain in the house, at least when we are there. We only work there on weekends so we don't touch the thermostat usually. The AC unit is under the house and I am not sure what type of heating unit he uses or if it is connected to the AC unit
    – Tai
    Commented Oct 14, 2022 at 19:19
  • ProTip™: Battery powered <things> do not just magically get charged by existing. They must, at some point, draw electricity from the wall somewhere, some how.
    – FreeMan
    Commented Oct 18, 2022 at 15:22

There is absolutely no way there is some sort of electrical spill causing your bill to go up.

electricity is not like a leaky faucet that making a water bill go up.

with zero information… the jacuzzi sounds suspect to me tbh


It would help if you told us what your bill was and now is, but taking a wild guess, a 600% increase will be 5 to 10 amps 24x7. That should be easy to find.

Start with the tub itself and the patio lights and outlets. Turn them off at the breaker and see if the power draw decreases. A clamp meter will help here. If you don't have one, buy a cheap one (as cheap as $12). Check the service wires and the circuits feeding the tub and outdoors. You will hopefully find one of them with high current, and can proceed from there.

  • 3
    So the original bill was 128 and it jumped up to around 800, and now it's even more than that right now. I unfortunately do not have the time right now to help my brother check and I don't think he has the ability to do it himself but I will go ahead and try your suggestion in two days when I head over. I'll comment on my findings later and thank you for your advice.
    – Tai
    Commented Oct 14, 2022 at 18:33

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