Over the last several years, we've had two power incidents that required repairs for our S P85.
The first time, the power company had an incident that cause a surge which damaged the secondary charger of our P85 and also something in the local power distribution. After this incident, only the primary charger (the early cars had dual 40A chargers) would work, limiting max charging to 40A - and when we connected to the power (through the HPWC, 14-50 outlet or standard 110 outlet), charging would run for a few minutes and stop. After lengthy discussions with Tesla and the local power company, the power company determined they was interference in the power, causing problems with Tesla chargers in the area - and after about a week they found the damaged equipment on their end and got us working again. And after Tesla replaced the failed onboard charger, we were able to again charge at 80A.
The second time was during Hurricane Harvey. We had another surge after the hurricane went through and we lost power. When power was restored our P85 gave us warning about charging. After several tries (connect/disconnect, power cycle the car), we were able to get the car charged. But when we evacuated to Austin, and the car refused to charge at the hotel's HPWC, Tesla had to repair the charging circuit.
We have surge protectors installed in the breaker boxes for the rest of the house - but not in the box we are using for the Tesla chargers.
When we had the first problem with the P85, Tesla claimed the onboard hardware had built-in surge protection, and that we shouldn't have to install any additional protection - the car should be able to handle variations in the power.
It's possible Tesla has added that protection after our P85 (VIN 3xxx) was built - because our S 100D wasn't affected by the power surge during Harvey.
However, after our P85 has now had two power-related incidents, and it's getting close to the end of our 100K mile warranty, we may have a surge protector added into the breaker panel for the Tesla charging.