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How many lights/watts can I put on a 15 Amp service?

Understanding Electrical Capacity​

Before diving into the specifics, it's essential to understand the basic concepts of electrical capacity. Electrical capacity refers to the maximum amount of electrical power that a particular circuit can handle safely. In our case, we are discussing a 15 Amp service, which means the circuit can handle up to 15 Amperes of current.

Calculating Wattage​

To determine how many lights or watts you can put on a 15 Amp service, you need to know the wattage of the lights you plan to install. Wattage is the unit of measurement for electrical power and is represented by the symbol "W." To calculate the wattage, you can use the formula:

Wattage = Voltage x Current (Amperes)

In most residential settings, the voltage is 120 volts. Therefore, for a 15 Amp service, the maximum wattage would be:

Wattage = 120 volts x 15 Amperes = 1800 Watts

Factoring in the 80% Rule​

To ensure electrical safety and prevent circuit overload, it's recommended to follow the 80% rule. This rule states that you should only use up to 80% of a circuit's maximum capacity. So, for a 15 Amp service:

Safe Wattage = 1800 Watts x 0.8 = 1440 Watts

This means that you should keep your total wattage below 1440 Watts to maintain a safe and efficient electrical system.

Determining the Number of Lights​

Now that you know the safe wattage for a 15 Amp service, you can calculate the number of lights you can install. To do this, divide the safe wattage by the wattage of each light you plan to install. For example, if you want to install 60-watt light bulbs:

Number of Lights = 1440 Watts / 60 Watts = 24 Lights

In this example, you can safely install 24 60-watt light bulbs on a 15 Amp service without exceeding the 80% rule.

Considerations for Energy-Efficient Lighting​

With the increasing popularity of energy-efficient lighting options, such as LED and CFL bulbs, it's possible to install more lights while still staying within the safe wattage range. For example, a 15-watt LED bulb may provide the same amount of light as a 60-watt incandescent bulb, allowing you to install more lights without overloading the circuit.

When planning your lighting installation, consider the wattage of the energy-efficient bulbs you plan to use and recalculate the number of lights accordingly.


Understanding how many lights or watts you can safely put on a 15 Amp service is crucial for maintaining a safe and efficient electrical system. By following the 80% rule and factoring in the wattage of your chosen light bulbs, you can confidently plan your lighting installation without the risk of overloading your circuit. Additionally, consider energy-efficient lighting options to further optimize your electrical system and reduce energy consumption.
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