How to Calculate Your Home’s Total Electrical Needs


Electricity is one area that confuses a lot of homeowners. Some don’t realize that if they have a 2,500 square foot home and they add 500 square feet, they may need to install an entirely new electrical system for the addition so the existing system isn’t strained beyond capacity. Here’s a quick guide for calculating the electrical needs of your home, and we’ll show an example after.

  1. Calculate Basic Needs – Multiply the square footage of all of the living areas by three watts. This is the base amount of power each room needs.
  2. Add 1500 – Add 1500 watts for each kitchen small appliance circuit and laundry room circuit. Include the coffee maker, microwave, food processor, mixer, blender, and any other small appliances you use in the kitchen.
  3. Add Wattages – The water heater, dryer, and range will be on their own circuit. Each of these appliances should have a nameplate or tag with wattage on it. If it doesn’t specify wattage, multiply volts times amps to get the wattage.
  4. Add 1-3 – Add the numbers you got during the first three steps. Figure the first 10,000 watts at 100% and the remaining at 40%.
  5. Add the Heating and Cooling – The heat pump or central AC, add whichever number is greater.
  6. Divide the Sum – Divide the sum, after adding all of the numbers above, by 230. This tells us how many watts our home needs.

For example:

  • 2,000 square foot home x 3 = 6,000 watts
  • Two small appliances in the kitchen plus one laundry room circuit = 3 x 1,500 = 4,500 watts
  • Water heater 5,000 watts, dishwasher 1,200 watts, dryer 5,500 watts = 11,700
  • (add these totals) = 22,200
  • The first 10,000 at 100% = 10,000 watts
  • The remaining 12,200 at 40% = 4,880
  • The subtotal is 14,880 watts
  • Add heating or cooling (whichever is greater) 4,000
  • Total = 18,800 watts
  • Divide the total 18,800 by 230 = 82amps

The standard 100 amp service will be enough for our example 2,000 square foot home with two kitchen appliances and a washer, water heater, dishwasher, dryer, and HVAC system. A 3,000 square foot home with more appliances may need a 200 amp service to provide sufficient electricity to all areas of the home.

If you’re concerned about the electrical system in your Essex area home or would like an electrical inspection, call us at 443-579-5701. We’ll schedule an appointment for a consultation and help put your mind at ease, whether the electrical system is fine or we see issues that need repair.