Skip to content 
Many solar energy storage installation service providers are unsure how many solar batteries to use for their homes. This involves return on investment and power supply capacity during power outages. If you choose an energy storage system that is too small, it won’t be able to support your household appliances; while blindly pursuing a high-power system wastes unnecessary energy storage.
Today, Hongyitai will guide you through the selection logic of solar panel batteries for homes, the solar battery calculation formula, and the factors influencing battery sizing for solar systems, so you can purchase the most suitable solar battery size.
This mainly involves the number of solar panels needed and the size of the energy storage batteries. The former represents the estimated amount of electricity they can generate, while the latter represents the amount of electricity you can actually use. Of course, you also need to roughly estimate your average daily electricity consumption, and then coordinate to arrive at the precise number and size of solar batteries.
The most typical combination for home energy storage is 5 kW solar panels + 10 kWh batteries, which can power small to medium loads such as refrigerators, lighting, routers, TVs, laptops, and washing machines.
- Small apartments / energy-efficient homes (5 kWh – 10 kWh): If you mainly use LED lights, laptops, and refrigerators, 1-2 battery banks are usually sufficient to cover nighttime electricity needs.
- Medium-sized homes (10 kWh – 20 kWh): Supports air conditioning, dishwashers, and dryers. This is the most common configuration for solar panel batteries for homes.
- Large / all-electric homes (30 kWh+): If you need electric vehicle charging stations, you will need a larger-scale module stack.
Factors affecting solar battery sizing
Simply calculating a household’s daily watt-hours isn’t enough. You also need to consider factors like winter and high loads. Here are 4 factors affecting battery sizing for a solar system:
- Peak load and discharge rate: Your home appliances don’t all run simultaneously. The instantaneous power consumption of an air conditioner or water pump starting up can be 3-5 times its operating power. You need the battery’s continuous discharge power to cover your peak demands.
- Ambient temperature constraints: Low temperatures (-0°C) significantly reduce battery discharge rates, while high temperatures (>60°C) accelerate battery aging. Many of our customers install solar battery systems in their garages, adding an extra 15% of redundant capacity.
- Depth of charge / discharge: Traditional lead-acid batteries can only use 50% of their capacity, while modern LiFePO4 batteries can safely be used at 80%-90%. As a lithium battery manufacturer, we design cells with a 10%-20% reserve capacity to ensure long-term normal operation when designing for our clients.
- Inverter energy loss efficiency: When direct current (DC) is stored in a battery and then converted back to alternating current (AC) for household appliances, there is a 10%-15% energy loss in this process. Your calculated total demand needs to be divided by 0.85 or 0.9 to determine the actual battery capacity you need to purchase.
Defining your home energy system goals
Different goals directly determine the scale of your battery sizing for a solar system. We categorize home energy storage into the following three most common use cases:
1. Self-consumption: Storing excess solar energy during the day for nighttime use, thus reducing reliance on the grid and lowering your electricity bills.
2. Emergency backup: Ensuring the continued operation of core appliances (refrigerator, lights, Wi-Fi, medical equipment) during grid outages. Commonly used in the southeastern United States and the Gulf Coast to prevent prolonged power outages due to natural disasters.
3. Off-grid living: This relies 100% on solar energy. To avoid three consecutive days of cloudy or rainy weather, it’s best to install an energy storage system with a daily power consumption of 3-5 times your average.
The step-by-step calculation formula
Step 1: Calculate Your Daily Total Power Consumption (Wh)
Below is a summary of the power consumption of common household appliances. You can assess your daily total power consumption based on your actual situation:
Formula: Power (W) × Operating Time (h) = Daily Power Consumption (Wh)
Step 2: Consider System Efficiency Losses
Energy is lost during the conversion from direct current (DC) to alternating current (AC). Based on our experience, you need to account for a 15% total power consumption loss.
Formula: Daily Total Power Consumption / 0.85 = Actual Required Capacity (Wh)
Step 3: Backup Power Days and Depth of Discharge (DoD)
If you want to maintain normal power supply even during consecutive rainy days, you need to multiply by the backup power days. At the same time, the optimal depth of discharge (80% – 90%) must be considered.
Formula: (Actual required capacity × Backup power days) / 0.8 = Final battery capacity requirement (Wh)
Step 4: Convert to battery pack quantity
Divide the final required battery capacity by the capacity of a single battery module. For example, for a 5kWh module, the number of battery modules you need equals the final capacity requirement / 5,120Wh.
In 2025, one of our Australian customers consumed 12kWh per day. Ignoring backup power days, we installed four 5kWh LiFePO4 battery packs for him. Now he can generate and consume his own electricity daily without paying any bills. If you are unsure how to calculate this, please refer to our energy storage battery section for specific solutions.
Analyzing your daily energy consumption
While the solar battery calculation formula above can give you a rough estimate of daily energy consumption, you can get more accurate data from your electricity bill.
Identify your peak usage. Don’t just look at the total electricity bill; look for the “total kWh consumed” on your bill. Divide your total monthly electricity consumption by 30. For example, if your monthly consumption is 450 kWh, your average daily electricity consumption is 15 kWh.
Identify base load and peak load. Refrigerators, routers, and security cameras consume power when operating 24/7, but washing machines, ovens, and vacuum cleaners require consideration of your specific usage frequency.
Like the load curve above, if you have a smart meter, you can view hourly electricity consumption data.
Lithium battery types
When choosing battery sizing for a solar system, the battery type directly determines the system’s footprint, safety level, and lifespan.
18650 vs. 21700 cylindrical cells: Mature technology, first used in Tesla’s Powerwall project, the 18650 battery has a smaller capacity but is extremely mature and cost-competitive. The 21700 battery has approximately 50% higher energy density than the 18650, meaning you can get a larger capacity in the same volume. We frequently use high-quality 21700 batteries in energy storage systems. You can see why 21700 batteries are commonly used in industrial products.
Prismatic & square cells: This is currently the mainstream choice for large-scale home energy storage systems (ESS). Their robust structure and large single-cell capacity (100Ah or 280Ah) make them ideal for assembling 5kWh or 10kWh wall-mounted or stacked batteries.
LiFePO4 has an extremely high thermal runaway temperature and poses no fire risk, which is crucial for solar panel batteries for homes. Rack-mounted storage allows for highly flexible expansion, facilitating future capacity increases. The all-in-one battery system is designed for modern homes, featuring a sleek, space-saving design and enhanced integration.
How to install solar energy storage system
We recommend hiring a licensed electrician to perform the following installation steps:
Choose a suitable location: The ideal installation environment is between 15°C and 30°C. Ensure installation in a dry, moisture-proof, and well-ventilated location (garage or dedicated power room), avoiding direct sunlight.
System voltage matching: Ensure the battery pack and inverter voltages are matched. Most modern home energy storage systems use 48V (or 51.2V) systems, which are easy to install in homes and have strong compatibility.
Ensure the battery’s BMS (battery management system) can communicate with your inverter (Victron, Growatt, Deye, etc.) via RS485 or CAN bus, allowing you to monitor battery health and SOC in real time.
A properly sized circuit breaker must be installed between the battery and the inverter. Ensure all racks and enclosures are reliably grounded to prevent static electricity buildup or leakage risks.
Your essential solar battery buying checklist
This checklist will ensure you avoid low-price traps and purchase genuine industrial-grade, high-quality solar home batteries. Please check against the following 5 core aspects:
1. Cell specifications: Cells account for over 70% of the total battery cost. Ensure the cells are Grade A brand new cells, avoiding the use of second-hand or Grade B cells.
2. BMS intelligent management system: Check if the BMS supports RS485/CAN communication and is compatible with most inverter brands.
3. Certifications and compliance: UN38.3, MSDS, CE, and RoHS certifications are mandatory.
4. Warranty and cycle life: All LiFePO4 batteries manufactured by Hongyitai should guarantee a cycle life of over 6000 cycles at 80% DoD, giving you peace of mind.
5. After-sales support and technical support: We provide wiring diagrams, BMS calibration software, and firmware update support.
