My house was recently struck by lightning. It fried several components of the HVAC system. Technician was able to restore operation, however the system does not cool anywhere near as crisp as it did before. And immediately after the strike, the energy usage has spiked and held consistent way above normal/average.

I have the thermostat set to 79 F to restrict cooling run time and have turned off or turned down practically everything else non-essential in the house. Daily power usage continues to be way above normal even with far less things running.

A separate air conditioning technician advised me that regardless of the system actually functioning, the compressor may be grounded resulting in weak cooling and high energy draw. I need serious help on this confounding situation as my electric bill has suddenly quadrupled over pre-strike usage. What are your professional opinions on this matter please?

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    Have you tried turning on only one circuit at a time at the breaker panel and seeing when the power meter shows a spike in usage? – ThreePhaseEel Aug 6 '17 at 16:07
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    Lighting can do strange things including compromising the insulation between the electrical conductors. This can happen in cables, fixtures and even inside motors. There can be cases where this compromise results in a short that consumes huge amounts of power but still limited to less than the breaker capacity. @ThreePhaseEel has exactly the right idea. Isolate the power consumption one circuit at a time and then when found follow up with the replacements necessary to get back to safe and economic operation. – Michael Karas Aug 6 '17 at 16:19
  • I have not done anything with individual circuits..yet...since it appears that everything is/was functioning normally. The "gauge" I'm going by is a daily bar graph report provided by my power company. The strike occurred on July 9..and immediately the next day the graph showed a spike in kWh usage..even with several components knocked out completely. I recently contacted the power company on the reasonable assumption that their "smart meter" had been affected. They claim it is reporting no trouble. I ordered them to come check in person and replace anyway. – Mark Aug 6 '17 at 17:01
  • After some reading and research, I have just about come to the conclusion that I should have the whole house megged. – Mark Aug 6 '17 at 17:01
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    Check the ground wire that runs from the circuit breaker panel to the grounding rods outside your house, look for the solid copper wire running from the ground strip and check for amperage in that wire using an "amprobe" type clamp on meter. If you have power (amperage) in that wire call a registered electrician. – d.george Aug 7 '17 at 16:45

Your excessive power draw can definitely be attributed to your hvac equipment having a faulty electrical component. Like others said, you need to shut the breakers off to the equipment and see if the power draw decreases over time to know for sure. Or you could have a technician check the equipment. The issue may not be your hvac system at all, however the fact that is is not cooling properly means it needs to be looked at by a professional.

Im not sure what type of system you have (condenser, Evaporator and air handler or furnace) but you need to have a technician check and test the compressor windings and motor windings of the condenser fan motor. It would also be wise to check to see if the blower motor for the indoor unit is still functioning properly. He should also check if anything is over amping. I would advise not using the unit until it is checked.


This usually means that the heaters are also on; something fried or fused. Test for voltage across the heater coils or control relay(s).

  • I don't know about usually, but it is definitely a possible could. Somehow the control circuit for, or the backup (or defrost) heaters themselves, are on. This would explain both the high power use and the poor cooling performance. – wallyk Aug 13 '17 at 5:06

Ok...since my last entry I have had the AC system checked. Compressor was deemed ok. Freon was low...resulting in frequent cycling on/off. That's confounding because the unit was cooling like a refrigerator at setpoint 79° before the lightning strike. How could the lightning have affected the refrigerant charge?? Secondly - a discovery: Pool pump timers were fried. Pumps running continuously since the incident. Didn't suspect them damaged since, at a glance, the pumps were running. Only the other day did I notice they weren't clocking. Replaced those .... With AC running properly and pumps back on timer control...power usage has dropped dramatically.

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    Are you the same user as the OP? If so, please merge your accounts so that you can gain rep, and edit your original post. – ThreePhaseEel Aug 13 '17 at 17:47

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