Holiday Light Calculator

String count and wattage from house dimensions and style.

Inputs

Linear Feet to Cover

Bulbs per String

String Length (ft)

LED? (0=Incandescent, 1=LED)

Hours per Day

Electric Rate ($/kWh)

Season Length (days)

Tab to move between fields

Results

Strings Needed

Total Wattage (W)

Total Bulbs400

Total Amps0.23

kWh per Day0.17

Monthly Cost ($)$0.66

Season Cost ($)$0.98

Circuits Needed1

Max Strings/Circuit205

How to Use This Calculator

Enter the total linear feet of roofline, trees, or pathways you want to cover.
Input the number of bulbs per string, the lit length of each string in feet, and select LED or incandescent.
Set daily run time in hours, electricity rate per kWh, and the season length in days.
Review strings needed, total wattage, and both monthly and season electricity costs.
Check the circuits needed output to avoid overloading your electrical panel.

How the result changes with Linear Feet to Cover

Linear Feet to Cover	Strings Needed	Total Wattage (W)
501	21	147
1,751	71	497
3,250	130	910
4,500	180	1,260

What each input means

Linear Feet to Cover: Total linear feet of roofline, trees, bushes, or pathways.
Bulbs per String: Number of bulbs on each string of lights.
String Length (ft): Lit length of each string.
LED? (0=Incandescent, 1=LED): LED uses ~0.07W/bulb vs ~0.5W for incandescent.
Hours per Day: Average daily run time.
Electric Rate ($/kWh): Your electricity rate per kilowatt-hour.
Season Length (days): Number of days lights will be on.

What each result means

Strings Needed: Number of light strings to purchase.
Total Bulbs: Total number of individual bulbs.
Total Wattage (W): Combined wattage of all lights.
Total Amps: Current draw at 120V.
kWh per Day: Daily electricity consumption.
Monthly Cost ($): Monthly electricity cost for lights.
Season Cost ($): Total electricity cost for the entire season.
Circuits Needed: Minimum 15A circuits required (at 80% load).
Max Strings/Circuit: Maximum strings safely on one 15A circuit.

How this is calculated

Worked example, using the default values

Identify Input Parameters
4 parameters
Linear Feet to Cover = 100, Bulbs per String = 100, String Length (ft) = 25, LED? (0=Incandescent, 1=LED) = 1 = 7 input(s) provided
Calculate Strings Needed
Strings Needed
4 = 4
Calculate Total Wattage
Total Wattage = totalBulbs * wattsPerBulb
28 = 28
Calculate Total Bulbs
Total Bulbs
400 = 400
Calculate Total Amps
Total Amps = totalWatts / 120
0.23 = 0.23

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