Powering Your Home with a Battery: What’s Feasible?

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If you’re exploring solar batteries, you probably have two key questions: How much of your home can a typical solar battery power, and for how long? The short answer is: it varies. Delve deeper into each question with our guide.

Factors Affecting the Power Capacity of Home Batteries

Determining the extent to which a battery can power your household involves primarily:

1. Assessing your power requirements.

2. Evaluating your battery’s power output.

Understanding basic electrical terms such as amps and kilowatts can aid in this assessment.

In simple terms:

Amps measure current, while kilowatts measure power.

To convert current to power, you multiply by voltage. In the US, homes typically have either a 120-volt or 240-volt electrical panel. To convert amps to watts, you multiply amps by voltage (then divide by 1,000 for kilowatts): at 120 Volts, 20 amps equals 2,400 Watts or 2.4 kW of power. Easy, isn’t it?

1. Identify Appliances/Circuits for Backup

To determine your power needs, list the appliances or circuits you want to back up. For whole-panel backup, which requires substantial power, you’d need a robust system. However, it’s rare to run all appliances simultaneously. Calculate power usage per appliance or circuit (most handle 15 to 20 amps) using resources like the US Department of Energy’s calculator. This helps estimate your home’s backup power requirements based on individual appliance wattages (e.g., 200W for a refrigerator, 20W per light bulb).

2. Determine Battery Power Rating

After assessing your power needs, focus on sizing your energy storage system. Consider two critical power metrics: instantaneous power and continuous power. Instantaneous power gauges if your battery can handle sudden power surges, crucial for appliances like pumps with high startup demands. For appliances with surge requirements, scrutinize this specification closely.

Continuous power denotes the steady power output (in kilowatts) your battery can sustain. This metric determines how many appliances and circuits you can power simultaneously for extended durations. Most batteries offer a continuous power rating ranging from 5 to 8 kilowatts, allowing for concurrent power supply to multiple circuits or several appliances.

Factors Affecting Battery Duration

When gauging how long your home can be powered by a battery, consider the following:

1. Usable Storage Capacity:

Know the amount of electricity your battery can store. Look for the usable storage capacity metric listed in kilowatt-hours (kWh). This figure indicates the capacity to utilize a specific power level (kW) over a set duration (hours).

For instance, with a battery boasting 10 kWh of usable storage capacity, you can either utilize 5 kilowatts of power for 2 hours (5 kW x 2 hours = 10 kWh) or 1 kW for 10 hours. Just like with your electronic devices, heavier usage depletes the battery faster.

2. Determining Appliance Usage

After establishing your battery’s usable capacity and understanding your appliances’ power consumption, the next step is to identify which appliances you intend to use and for how long. Here’s a breakdown based on a battery with 10 kWh usable capacity:

– A 3,500 W air source heat pump can run for under 3 hours.

– A 300 W TV can run for 33 hours.

– A 200 W refrigerator can run for 50 hours.

– Five 20 W light bulbs can run for 100 hours.

– A 25 W phone charger can run for 400 hours.

– A 6 W WiFi router can run for 1,600 hours.

Given you’ll likely operate multiple appliances simultaneously, there are trade-offs to consider. For example, running the TV for two hours might reduce the refrigerator’s runtime by three hours. However, if you prioritize essentials like phones, computers, WiFi, refrigerator, and lights during an outage, a 10 kWh battery can sustain them for nearly 24 hours.

Solar Pairing Considerations

The decision to pair your battery with solar hinges on the duration and frequency of grid outages you experience. Here’s what to consider:

Standalone Battery: Ideal for frequent but brief outages, providing backup power until grid service is restored. Not suitable for prolonged outages lasting a day or more.

Solar Integration: Pairing solar panels with storage ensures indefinite backup power as long as sunlight is available. Even on cloudy days, solar recharge capability remains, sustaining your home’s energy needs.

Given the limited power output of batteries, most installations feature a critical load panel and a secondary electrical panel with fewer circuits. This setup prevents overloading and damage to the battery during simultaneous high-demand events, like running the AC and washing machine together.

Alternatively, incorporating a load management device—such as Span, Schneider, Generac, or Lumin energy management systems—eliminates the need for critical load panels. These systems optimize battery usage, allowing almost every circuit to be backed up safely.

Determining Battery Usage

Calculating how much of your home you can power with a battery and for how long involves understanding your energy needs and the capabilities of your battery:

Power consumption

Consider the power requirements of various appliances. For instance, a refrigerator typically starts at 800 W and runs at 200 W.

Battery capacity

Evaluate the continuous power rating of your battery. A 5 kW battery can simultaneously power multiple appliances.

Duration of usage

Assess how long you plan to use each appliance. Extended usage reduces stored energy available for other appliances.

For instance, with a 5 kW battery, you might power a refrigerator, cell phone chargers, WiFi router, lights, TV, microwave, and more concurrently. However, running power-intensive appliances like an AC unit (5 kW) or washing machine (800 W) for extended periods may deplete stored energy rapidly.

Keep in mind your battery’s usable energy storage, typically around 10 kWh. To optimize usage, use battery monitoring apps to track remaining battery life under different scenarios and conditions.

If you’re considering a solar-plus-storage system for backup power, the first step is to request personalized quotes from nearby solar and storage providers. Discover the potential savings from solar energy and the security of backup storage. Get started today!