How much voltage is too high?
Voltages over approximately 50 volts can usually cause dangerous amounts of current to flow through a human being who touches two points of a circuit, so safety standards are more restrictive around such circuits. In automotive engineering, high voltage is defined as voltage in range 30 to 1000 VAC or 60 to 1500 VDC.
The acceptable voltage range in the US is typically +5% to -10 %. This would be 108-126 volts on a basis of 120 volts nominal. Be aware that the voltage at an outlet will vary based on load (both yours and others on the same feeder).
For power applications the voltage is double, so between 228 and 252 Volts, should be "normal".
If the line voltage at your home is 250v, then it is considered very high. You need to use voltage stabilizers to control the voltage to your electronic devices. Your electronic devices mention the adequte voltage range normally on the Serial number tag/ label (something like 210v to 240v).
At the electrical service, the electric utility should attempt to keep the voltage ±5% of nominal. The electrician needs to be aware of the acceptable electric utility fluctuation and plan to keep the voltage at the point of utilization between +5/-10% of nominal.
The most common electrical outlet in any home is a 110 volt. Sometimes you may hear 110 volt plugs referred to as 120 volt.
For some alternators, it's normal to see as low as 13 volts. For some, a constant 13.6 volts is an indication of a problem. For others, it's normal to see as high as 16 volts for long stretches. Still, it's perfectly normal for others to see the alternator not charge at all intermittently.
The main cause of these voltage surges in power system are due to lightning impulses and switching impulses of the system. But over voltage in the power system may also be caused by, insulation failure, arcing ground and resonance etc.
- Install a Whole-House Surge Protector. ...
- Have Added Protection for Specific Devices. ...
- Upgrade Your AC Unit. ...
- Unplug Devices During a Storm. ...
- Inspect Your Wiring.
Home Voltage
As rated by the IEC, home electrical wiring is considered low voltage. However, housing voltage, which is from 100 to 250 VAC, is considered high voltage for home owners. Consequently, 5 to 24 volt devices are considered low voltage in homes.
Is 15 volts too high?
So, to answer your question, Yes, 15 volts is too high. Most car alternators, that normally recharge your battery after every start, and provide power while the engine is running, are normally voltage regulated to about 13.8 to 14.0 volts.
Even contact with standard 110-volt circuits can be lethal under certain conditions. Hand-to-hand, hand- or head-to-foot, and ear-to-ear current paths are the most dangerous because they may cause severe damage to the heart, lungs and brain.

Yes it is still dangerous. People can be electrocuted by coming into contact with 100-200 volts and there have been reports of injuries or death resulting from being shocked with as little as 42 volts.
120V is known as high voltage, line voltage or standard voltage. This is the voltage that comes directly into most homes.
If your battery has a charge between 12.4V and 12.7V, your battery is fully charged and ready to run. If your voltage is below 12.2V, it needs to be recharged. Take a 30-minute drive on the highway or pick up a charger to bring the voltage back up. If your voltage is higher than 12.9V, the battery is overcharged.
To fully charge in reasonable times, alternator output must be 14.2 V to 14.5 V as measured right across the battery posts. Above 14.5 volts charging voltage, batteries have a greatly increased tendency to release excessive acidic vapors, hydrogen gas, and to corrode things around the battery.
Higher than 15 volts indicates a fault in the charging system's voltage regulator or related circuits. If it's substantially excessive, this can cause electrical system and/or battery damage.
The human body feels a shock when the voltage is higher than about 3,500 volts. Walking over a carpet can generate 35,000 volts. The Electrostatic Discharge (ESD) from this voltage can cause pain. The discharge is not life threatening but it still hurts.
Ordinary, household, 120 volts AC electricity is dangerous and it can kill.
It is sometimes suggested that human lethality is most common with alternating current at 100–250 volts; however, death has occurred below this range, with supplies as low as 42 volts.
How many volts is a police taser?
Stun guns, which have been used by law enforcement for decades, can temporarily immobilize a person — think of someone who is combative or resisting arrest, for instance — by jolting them with 50,000 volts of electricity.
So yes, 220 Volts is plenty to kill you if the source can supply sufficient current, and if that killed you you would have been “electrocuted". However if you are only injured and not killed by the electricity you would not have been “electrocuted". =220/5000=0.044 amps very close to 50mA (0.050 amps) probably lethal.
If you routinely grab exposed conductors barehanded by their insulation to install wire nuts, you're putting yourself at high risk for electrocution. If it's a 277V circuit, chances are you won't be able to let go. And without GFCI protection or someone present to administer CPR right away, you may end up dead.
Voltage Ranges
We all know that electricity can be dangerous– even low voltage. Low voltage ranges from 0 to 50 volts, while high voltage ranges from 1,000 to 500,000 volts.
Rule 2-106 prescribes 150 volts-to-ground as the maximum voltage in dwelling units. A dwelling unit is where we live, such as a single family home, townhouse or apartment. It follows that this rule limits the supply voltages to dwelling units to either 120/240 volts single-phase or 120/208 volts three-phase.