Whole House Battery System Calculator

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:

watt-hours

Days of Autonomy:

days

Battery Voltage:

volts

Depth of Discharge:

decimal (0-1)

Efficiency:

decimal (0-1)

Battery Capacity:

Unit Converter ▲

Unit Converter ▼

From:	To:

1. What is the Whole House Battery System Calculator?

The Whole House Battery System Calculator estimates the required battery capacity (in ampere-hours) to power your home based on your daily energy needs, desired days of autonomy, 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 household's typical daily energy use in watt-hours
Days of Autonomy — How many days you want the battery to last without recharging
Battery Voltage — The nominal voltage of your battery bank (typically 12V, 24V, or 48V)
Depth of Discharge — The percentage of battery capacity you can safely use (typically 0.5-0.8)
Efficiency — The system's overall efficiency (typically 0.85-0.95)

Explanation: The formula calculates how much battery capacity you need to cover your energy needs for the desired period, accounting for system losses and safe battery usage limits.

3. Importance of Battery Capacity Calculation

Details: Proper battery sizing is crucial for ensuring your home has enough power during outages or off-grid periods, while avoiding unnecessary costs from oversized systems.

4. Using the Calculator

Tips:

Measure or estimate your daily energy consumption from utility bills or energy monitors
Choose days of autonomy based on your needs (3-5 days is typical for backup systems)
Use manufacturer specifications for battery voltage and recommended depth of discharge
Account for system efficiency (typically 85-95% for modern systems)

5. Frequently Asked Questions (FAQ)

Q1: How do I determine my daily energy consumption?
A: Check your electricity bills for monthly kWh usage, divide by 30, then multiply by 1000 to get watt-hours. For more accuracy, use an energy monitor.

Q2: What's a typical depth of discharge for batteries?
A: Lead-acid batteries typically use 50% DoD, while lithium-ion can often use 80-90% DoD.

Q3: Why include efficiency in the calculation?
A: Efficiency accounts for losses in the inverter, charge controller, wiring, and battery charging/discharging.

Q4: Should I round up the calculated capacity?
A: Yes, it's recommended to round up to the nearest available battery size and consider future energy needs.

Q5: Can I connect multiple batteries to achieve the needed capacity?
A: Yes, batteries can be connected in series (to increase voltage) or parallel (to increase capacity).