Whole House Battery Backup Sizing

Battery Capacity Equation:

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

Load Power:

watts

Required Backup Time:

hours

Battery Voltage:

volts

Depth of Discharge:

decimal (0-1)

Efficiency:

decimal (0-1)

Required Battery Capacity:

Unit Converter ▲

Unit Converter ▼

From:	To:

1. What is Whole House Battery Backup Sizing?

Whole House Battery Backup Sizing calculates the required battery capacity (in ampere-hours) needed to power your home for a specified duration during an outage, considering your power requirements and battery system characteristics.

2. How Does the Calculator Work?

The calculator uses the battery capacity equation:

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

Where:

Load Power — Total wattage of all devices you need to power
Required Backup Time — Hours of backup power needed
Battery Voltage — System voltage (typically 12V, 24V, or 48V)
Depth of Discharge — Fraction of battery capacity you can safely use (typically 0.5-0.8)
Efficiency — System efficiency including inverter losses (typically 0.85-0.95)

Explanation: The equation accounts for your power requirements and adjusts for battery system characteristics to determine the minimum battery capacity needed.

3. Importance of Proper Battery Sizing

Details: Proper battery sizing ensures your backup system can meet your power needs without over-discharging batteries (which reduces lifespan) or under-sizing (which leaves you without power).

4. Using the Calculator

Tips:

Calculate your total load power by summing the wattage of all essential devices
For depth of discharge, use 0.5 for lead-acid, 0.8-0.9 for lithium batteries
Typical efficiency is 0.9 for systems with good inverters
Always round up your calculated capacity to the nearest available battery size

5. Frequently Asked Questions (FAQ)

Q1: How do I determine my total load power?
A: Sum the wattage of all devices you want to power simultaneously. Check appliance labels or use a wattmeter for accurate measurements.

Q2: What's a typical depth of discharge?
A: 50% for lead-acid (to extend lifespan), 80-90% for lithium batteries.

Q3: How does battery voltage affect the calculation?
A: Higher voltage systems require fewer amp-hours for the same energy storage (watt-hours).

Q4: Should I add a safety margin?
A: Yes, add 10-20% to account for battery aging and unexpected loads.

Q5: How do I convert Ah to kWh?
A: Multiply Ah by battery voltage and divide by 1000 (kWh = Ah × V / 1000).