Battery Sizing Calculator 2026: How Much Storage Do You Need?
Size My Home Battery
Your Battery Backup System
Sized for your energy needs
Return on Investment
Next Steps: Adding Storage
- 1→Learn the basics & system typeNew to storage? Our Battery Basics guide covers how home batteries work, chemistry, and coupling. Our Battery Types guide helps you pick the right system before you shop.
- 2→Check available incentivesReview active state and utility programs in our Battery Incentives guide — the federal credit expired Dec 31, 2025.
- 3→Add solar for indefinite backupPair storage with panels so the battery recharges daily. Try our Solar Savings Calculator.
- 4→Get installer quotesCompare price per kWh of usable capacity, warranty terms, and software. Ask each installer about current state and utility rebate programs before you sign.
Battery Sizing Calculator: How Much Storage Do You Need?
Use this Battery Sizing Calculator to find the right battery capacity for your home. Enter your daily energy usage, solar system size (or 0 if you don't have solar yet), and desired backup duration for an instant recommendation — including how many Tesla Powerwalls you need and the total installed cost.
Home battery storage is one of the fastest-growing home-energy investments in the US. Outages are increasing and electricity rates keep rising — though note that the federal Section 25D tax credit expired December 31, 2025 and no longer applies to new installations. Whether you want backup protection, solar self-consumption, or energy independence, this Battery Sizing Calculator shows what you need and what it actually costs today.
What to Enter & Why It Matters
Daily Energy Usage (kWh/day): Check your electricity bill for your average daily kWh. The US average is about 30 kWh/day. To power essential loads only (refrigerator, lights, WiFi, medical devices) during an outage, enter 30–40% of your total — often 10–12 kWh — to cut system cost while keeping critical appliances running.
Solar System Size (kW): Enter your existing or planned solar size, or 0 if none. With solar, your battery recharges daily for potentially indefinite backup rather than a single discharge cycle.
Backup Duration: How many hours of backup you want. 24 hours covers most short outages; 72+ hours protects against multi-day outages common in hurricane or ice-storm zones.
Grid-Tied vs Off-Grid: Which Is Right for You?
A grid-tied battery system stays connected to the utility grid, storing solar energy and discharging at night or during peak pricing. During outages it switches to battery power and recharges with solar — the most common, cost-effective setup for most homes.
An off-grid battery system runs independently of the grid. It needs significantly more capacity (3+ days of autonomy) and a large enough solar array to meet 100% of your needs year-round. Off-grid costs more but is essential for remote properties without grid access.
Frequently Asked Questions
For whole-home backup, size the battery to your daily kWh use and desired backup hours. For essential loads only (fridge, lights, WiFi), 30–40% of daily usage — often 10–12 kWh — keeps critical appliances running at much lower cost. The calculator sizes it from your own numbers.
Yes — most modern inverters support AC-coupled battery storage. A solar-plus-battery retrofit typically costs $10,000–$20,000 installed before incentives.
Most home batteries carry a 10–15-year manufacturer warranty and are rated for 4,000–6,000 charge cycles. Real-world lifespan is typically 15–20 years with proper management.
Each Powerwall 3 stores 13.5 kWh. Your total depends on daily usage, backup hours, and whether you have solar — the calculator rounds your recommended capacity up to whole units.
No. A battery can charge from the grid alone and still provide backup power during outages — select Grid-Tied above and enter 0 for solar size. Adding solar later lets the same battery recharge for free instead of from grid power.
Since the federal Section 25D credit expired December 31, 2025, your net cost now depends entirely on state and utility programs like California's SGIP or Massachusetts' SMART. See our Battery Incentives guide for what's active in your state.
Installed costs in 2026 typically run $10,000–$20,000 for a single-battery system. A Tesla Powerwall 3 (13.5 kWh) installs for roughly $12,000–$15,000 all-in; an Enphase IQ Battery 5P (5 kWh) for $8,000–$11,000. Battery costs per kWh have dropped significantly over the past five years and continue to fall. The U.S. Department of Energy tracks storage cost trends and publishes regular updates.
Most home batteries mount on an interior or exterior wall near your main electrical panel — typically in a garage, utility room, or on an exterior wall. They must stay within temperature limits (usually 32°F–104°F / 0°C–40°C), so avoid uninsulated spaces in extreme climates. Some models like the Tesla Powerwall 3 are outdoor-rated; others require a covered location. Your installer will assess the best spot during the site visit.
Our Battery Sizing Calculator uses your actual daily kWh usage, backup hours, and solar size to estimate capacity, not a generic per-square-foot rule of thumb. It rounds your recommendation up to whole battery units (Powerwall, Enphase IQ, or LG RESU) and pulls current 2026 installed pricing, so the numbers reflect real market costs rather than outdated averages. That said, it's a planning tool, not a final quote — actual pricing depends on your roof, panel, electrical work, and permitting needs. Most homeowners use the Battery Sizing Calculator results to compare a few installer quotes with realistic expectations already in hand.