The amount of amps a normal house needs depends on several factors, including the size of the house, the number and types of electrical appliances and equipment, and the electrical service coming into the home. Having an adequate electrical service with enough available amps is crucial for powering all the lights, appliances, and devices in a home safely and efficiently. Understanding amps, circuits, and calculating electrical loads allows homeowners to determine if their home’s electrical system can handle current and future needs.
What are Amps?
Amps, short for amperes, measure the flow of electrical current. The higher the amp rating on an electrical circuit or device, the more current it draws. Amps measure how strong the flow of electricity is at any given point.
Fuses and circuit breakers control the amps on their electrical circuits. If too many amps are drawn on a circuit, the fuse blows or the breaker trips to stop the flow of excessive current and prevent wires from overheating.
The main electrical service coming into a house is supplied with a certain amp capacity. This is determined by the size of the wiring, circuit breakers, and other factors. Typical residential electrical services are sized at 100, 150, or 200 amps.
Key Factors Determining Electrical Needs
The main factors that determine how many amps are needed for a house are:
House Size
Larger homes require more amps than smaller ones. More square footage means more lights, outlets, and appliances needing power. Newer large homes often have 200 amp electrical panels, while older or smaller homes might have only 60-100 amps.
Number of Circuits
The number of branch circuits in a house impacts amp needs. More circuits allow household power to be divided into separate paths powering fewer lights/outlets per circuit. This avoids overloading any one circuit. Modern homes usually have at least 20 circuits.
Major Appliances
Larger appliances like electric stoves, ovens, clothes dryers, and air conditioners require 20-50 amp dedicated circuits. The more sizeable appliances a house has, the higher its overall amps needs will be.
Electronic Devices
The proliferation of computers, home entertainment systems, game consoles, and other electronic devices has dramatically increased average home power usage. While each device draws less than major appliances, collectively they contribute to higher amp requirements.
Lighting Needs
The amount of lighting, type of bulbs, and use of lighting controls impacts amperage needs. More lights equal more amps. Incandescent bulbs use more power than LEDs. Smart home technology like motion sensors and dimmers can reduce lighting power demands.
Calculating Electrical Load
To determine how many amps are needed, the average amp draw of all electrical devices/appliances that could possibly be on at the same time must be calculated. This is called calculating the electrical load.
Here are the main steps:
1. Make a list of all hardwired appliances and their amp rating typically noted on a label or placard on the device.
2. Determine the wattage of all plug-in appliances and devices and convert watts to amps by dividing watts by 120 (the standard household voltage in the US).
3. Add up the amps needed for all lighting. Allow 1.5 amps per lighting fixture as an estimate.
4. Add up the amp ratings off all appliances, devices, and lighting needed to find the total electrical load.
As an example:
Appliance / Device / Lighting – Amps Needed
Electric oven – 40 amps
Electric range – 50 amps
Clothes dryer – 30 amps
Dishwasher – 15 amps
10 Recessed lights – 15 amps (1.5 each x 10)
3 Bedroom circuits – 15 amps each x 3 = 45 amps
4 Bathroom circuits – 20 amps each x 4 = 80 amps
Kitchen circuits – 50 amps
Washer circuit – 20 amps
Furnace – 10 amps
Pool pump – 15 amps
Entertainment/computer equipment – 15 amps
Misc. outlets – 15 amps
Total Amps Needed = 380 amps
As the example shows, all the needed amps add up quickly in a typical home. Safety requires adding an extra 20-25% margin beyond the calculated load to allow for future expansion. So for the load above, the service would need to provide around 450-475 amps to comfortably meet the house’s needs.
200 Amp Service for Most Homes
For a medium to large single family house with central air, electric appliances, modern electronics and lighting, a 200 amp main service is usually recommended. This provides enough power for all typical home needs while allowing for some expansion. Services smaller than 150 amps can potentially leave a house underpowered.
Upgrading an old 60-100 amp panel to 200 amps is a common improvement homeowners make when rewiring or renovating an older home. The relatively small cost of this upgrade provides enhanced safety, capacity, and resale value.
Some very large custom homes do require services exceeding 200 amps, even up to 600 amps for houses over 10,000 square feet with an extreme number of appliances and systems. But 200 amps covers the needs of most typical single family homes 2500-4500 square feet in size comfortably.
Apartments and condos have lower amperage requirements, as they share electrical service with other units. Individual units might have 60-125 amp panels.
120/240 Volt Service
While the main electrical service amperage rating is an important factor, the incoming voltage provided by the utility company also impacts power availability.
Most homes have 120/240 volt single phase power:
– 120 volts supplied for lighting circuits, outlets, small appliances.
– 240 volts for large appliances like water heater, range, dryer, AC condenser.
Larger homes sometimes have 208 volt 3-phase power or even higher 480 volt services to better power centralized equipment like HVAC systems, pool equipment, outbuildings, etc. But 120/240V single phase is standard for the majority of residential needs.
Circuit Breaker Box
The home’s main circuit breaker box or panel matches the amp rating of the incoming electrical service. A 200 amp service requires a panel with a 200 amp main breaker. Separate circuit breakers in the panel then distribute power safely to different circuits around the home.
Sufficient circuit breaker spaces for all the home’s circuits is vital. A 200 amp panel will typically have 24-40 circuit breaker poles. If all the spaces get used up, it becomes impossible to add new circuits for upgrades and expansions. So a panel with room to grow is wise.
Other Electrical Considerations
Beyond the main service amps and panel, other electrical factors also impact if a home’s power needs are met:
Wire Gauge
Thick wires are needed to handle high amp loads. Wire must be sized correctly for the amperage on a circuit to prevent fire hazards.
Conductor Material
Copper wiring is standard. More conductive aluminum can sometimes be used for very large feeds but has different capacity limits.
Grounding
A proper grounding system and ground wires in all circuits are essential for safety. This prevents shocks and allows fault protection to work.
Receptacles and Switches
Outlets and switches must be rated to handle their circuit’s designed amp load. A standard 15 amp receptacle cannot safely power a 20 amp circuit, for example.
Distance from Panel
Voltage drop can occur when circuits are very long, reducing available power. Wire size must be increased for long runs.
Calling an Electrician
Determining your home’s electrical needs can be complicated. If your existing service is outdated or you’re planning significant upgrades or additions, it’s wise to have a professional electrician calculate the required capacity and design the electrical system.
They have the specialized knowledge, tools, and experience to ensure your home’s power infrastructure meets all electrical code requirements and provides sufficient power for safe, reliable operation of all your home’s electrical systems and devices.
Conclusion
The standard for most single-family homes is a 200 amp, 120/240 volt electrical service. This provides adequate power for lighting, central AC, appliances, electronics and future expansion. Careful load calculations help determine if more or less amps may be needed for very small or very large homes.
An experienced electrician can analyze your home’s size, systems and electrical usage to determine the ideal service capacity, wiring gauge, circuit breaker panel size, and other details tailored for your house’s unique needs while ensuring full compliance with electrical codes for safety. They can then make any necessary upgrades or changes to provide your household with reliable, sufficient electrical power for daily needs and growth long into the future.
