Whole House Battery Backup Calculator For Solar

Battery Capacity Formula:

\[ \text{Battery Capacity (Ah)} = \frac{\text{Daily Energy Consumption (Wh)} \times \text{Days of Autonomy}}{\text{Battery Voltage (V)} \times \text{Depth of Discharge} \times \text{Efficiency}} \]

Daily Energy Consumption:

Days of Autonomy:

days

Battery Voltage:

Depth of Discharge:

decimal (0-1)

System Efficiency:

decimal (0-1)

Required Battery Capacity:

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1. What is Battery Capacity Calculation?

The battery capacity calculation determines the required battery bank size (in amp-hours) needed to power your home for a specified number of days without solar input, considering your daily energy usage, battery specifications, and system efficiency.

2. How Does the Calculator Work?

The calculator uses the following formula:

\[ \text{Battery Capacity (Ah)} = \frac{\text{Daily Energy Consumption (Wh)} \times \text{Days of Autonomy}}{\text{Battery Voltage (V)} \times \text{Depth of Discharge} \times \text{Efficiency}} \]

Where:

Daily Energy Consumption — Your total daily electricity usage in watt-hours
Days of Autonomy — Number of days you want backup power without solar charging
Battery Voltage — System voltage (typically 12V, 24V, or 48V)
Depth of Discharge — Maximum safe discharge level (usually 0.5-0.8)
Efficiency — System efficiency factor (typically 0.8-0.95)

Explanation: The formula accounts for your energy needs, desired backup duration, battery specifications, and system losses to determine the minimum battery capacity required.

3. Importance of Proper Sizing

Details: Correct battery sizing ensures reliable backup power, prevents premature battery failure from over-discharge, and optimizes system cost and performance.

4. Using the Calculator

Tips: For accurate results, use actual consumption data from your utility bill or energy monitor. Typical values: DoD 0.5-0.8, Efficiency 0.85-0.95. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is a typical daily energy consumption?
A: Average US home uses about 30kWh/day, but solar homes often use 10-20kWh/day with efficiency measures.

Q2: How many days of autonomy should I plan for?
A: 1-3 days is typical, depending on your location's weather patterns and reliability needs.

Q3: What depth of discharge is safe for my batteries?
A: Lead-acid: 50-80%, Lithium-ion: 80-100%. Check manufacturer specifications.

Q4: Why include system efficiency?
A: Accounts for losses in inverters, wiring, and battery charge/discharge cycles (typically 10-20% loss).

Q5: Should I add a safety margin?
A: Yes, consider adding 10-20% to the calculated capacity for aging and unexpected loads.