Home Battery Size Calculator

Home Battery Size Formula:

\[ Capacity_{kWh} = \frac{Daily\ Usage_{kWh} \times Autonomy\ Days}{Depth\ of\ Discharge} \]

Required Battery Capacity:

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1. What is Home Battery Sizing?

Home battery sizing calculates the required battery capacity to meet your energy needs for a specified number of days (autonomy) while considering the battery's depth of discharge. Proper sizing ensures reliable power supply during outages or off-grid operation.

2. How Does the Calculator Work?

The calculator uses the home battery size equation:

\[ Capacity_{kWh} = \frac{Daily\ Usage_{kWh} \times Autonomy\ Days}{Depth\ of\ Discharge} \]

Where:

\( Daily\ Usage_{kWh} \) — Your average daily electricity consumption
\( Autonomy\ Days \) — Number of days you want the battery to last
\( Depth\ of\ Discharge \) — Fraction of battery capacity that can be safely used (typically 0.5-0.9)

Explanation: The equation calculates the total energy needed (daily usage × days) and divides by the usable fraction of the battery capacity.

3. Importance of Proper Battery Sizing

Details: Correct battery sizing ensures you have enough power when needed without overspending on unnecessary capacity. Undersizing leads to power shortages while oversizing increases costs unnecessarily.

4. Using the Calculator

Tips: Enter your average daily electricity usage in kWh, desired number of days the battery should last, and the depth of discharge (typically 0.8 for lithium batteries). All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is a typical depth of discharge for batteries?
A: Lithium-ion batteries typically allow 80-90% DoD, while lead-acid batteries should only be discharged to 50%.

Q2: How do I determine my daily usage?
A: Check your electricity bills for monthly kWh usage and divide by 30. For more accuracy, use smart meter data.

Q3: What's a reasonable autonomy period?
A: For grid-tied systems, 1-3 days is common. Off-grid systems may need 3-7 days depending on location and backup options.

Q4: Should I add a safety margin?
A: Yes, consider adding 10-20% to account for battery aging, temperature effects, and unexpected usage increases.

Q5: Does this account for solar charging?
A: No, this calculates total storage needed. For systems with solar, you'd need to account for daily solar input as well.