Whole Home Battery Backup Calculator

Battery Capacity Formula:

\[ \text{Battery Capacity (Ah)} = \frac{\text{Whole Home Load (W)} \times \text{Backup Time (h)}}{\text{Battery Voltage (V)} \times \text{Depth of Discharge}} \]

Whole Home Load (watts):

Backup Time (hours):

Battery Voltage (volts):

Depth of Discharge (decimal):

(0-1)

Required Battery Capacity:

Unit Converter ▲

Unit Converter ▼

From:	To:

1. What is the Battery Capacity Formula?

The battery capacity formula calculates the required battery bank size (in amp-hours) needed to power your home's electrical load for a specified backup time, considering the battery voltage and depth of discharge.

2. How Does the Calculator Work?

The calculator uses the following equation:

\[ \text{Battery Capacity (Ah)} = \frac{\text{Whole Home Load (W)} \times \text{Backup Time (h)}}{\text{Battery Voltage (V)} \times \text{Depth of Discharge}} \]

Where:

Whole Home Load — Total power consumption of your home in watts
Backup Time — Desired duration of backup power in hours
Battery Voltage — Nominal voltage of your battery bank (typically 12V, 24V, or 48V)
Depth of Discharge — Fraction of battery capacity that can be safely used (typically 0.5-0.8)

Explanation: The formula converts your power requirements into battery capacity while accounting for system voltage and how much of the battery's capacity you can actually use.

3. Importance of Proper Battery Sizing

Details: Correctly sizing your battery bank ensures you have sufficient backup power while avoiding unnecessary costs from oversizing. It also helps maintain battery health by operating within recommended discharge limits.

4. Using the Calculator

Tips:

Measure or estimate your home's total power consumption in watts
Determine how many hours of backup you need
Know your battery system voltage (common home systems use 24V or 48V)
Use manufacturer-recommended depth of discharge (typically 50-80%)

5. Frequently Asked Questions (FAQ)

Q1: What's a typical depth of discharge for lead-acid vs lithium batteries?
A: Lead-acid: 50% recommended, Lithium: 80-90% possible.

Q2: How do I determine my whole home load?
A: Add up wattage of essential appliances or use your electric bill's kWh usage to estimate.

Q3: Why does battery voltage matter?
A: Higher voltage systems are more efficient for whole-home applications, reducing current and wire sizes.

Q4: Should I add a safety factor?
A: Yes, consider adding 10-20% to account for inefficiencies and future needs.

Q5: How does temperature affect battery capacity?
A: Cold temperatures reduce available capacity - you may need to oversize in cold climates.