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How Many Batteries To Power A House

When harnessing solar energy for your home, understanding your area’s average monthly solar power generation is crucial. Solar power generation varies significantly based on your geographical location and the number of sunlight hours you receive. This variation can impact your energy savings and the number of solar panels and batteries needed. Let’s delve into the key factors that influence your solar power equation.

Sunlight Hours in Your Region

The first factor to consider is the number of sunlight hours your region experiences. Solar power generation is directly linked to sunlight availability. Some areas bask in 5-6 hours of daily sunlight, while others enjoy 8-9 hours or more. Depending on these sun hours, your average monthly solar power generation can range from 80 to 130 kilowatts per hour. It’s worth noting that this range can fluctuate based on the intensity of sunlight, particularly in seasons like summer and monsoon.


Power Consumption

You need to assess your power consumption to determine the optimal number of solar panels and batteries required to power your home. Calculate the average power consumption over the past 12 months by summing up the energy units used each month and dividing the total by 12. Remember that this calculation should be based on power consumption units, not monetary amounts. Understanding your home’s energy needs is fundamental in designing an efficient solar energy system.

Types Of Solar Batteries

Within the realm of solar power, an array of solar energy accumulators exists, each endowed with distinctive traits and intricacies. Grasping the nuances of these diverse solar accumulators becomes pivotal in rendering an enlightened selection. Here is an elaborate exploration of the most prevalent categories:

Lead-Acid Batteries

The lineage of solar energy accumulators heralds the advent of Lead-Acid Energy Cells, renowned for their economic appeal. Nevertheless, these cells bear the weight of a truncated lifespan when juxtaposed with choices, demanding punctilious upkeep. Moreover, they encompass perilous constituents necessitating cautious manipulation and disposal.


Lithium-Ion Energy Cells reign supreme in contemporary times, epitomizing the preferred choice. They endow the user with exalted energy reservoirs, meager upkeep prerequisites, and facile setup. Regrettably, this exquisite utility comes at a premium cost compared to its counterparts, with Blue Sky Electric exhibiting a penchant for this battery variant.


The Nickel-Cadmium (NiCd) Energy Cells bear semblances to Lithium-Ion counterparts concerning robustness and dependability. Nonetheless, they are saddled with a curtailed lifespan and embrace an ecological hazard status, mandating scrupulous handling in installation and disposal.

Flow Batteries

Flow Energy Cells, a paragon of prolonged energy retention, preserve copious quantities of energy over protracted periods. This system operationalizes two tanks ensconcing electrolytic solutions, orchestrating a fluidic exchange within a central cell stack during both the charging and discharging phases. Their dimensions often transcend the realms of modesty, occasionally encompassing entire chambers, thereby commanding an elevated initial expenditure owing to their voluminous nature and intricacy.

Sealed AGM Batteries

Sealed absorbed glass mat (AGM) energy cells offer an almost maintenance-free experience, given that all constituents remain hermetically ensconced within the enclosure. They commonly exhibit a protracted lifespan when juxtaposed with their counterparts and commanding minimal installation acreage. Nevertheless, the sophisticated attributes of AGM systems may concomitantly translate into an augmented preliminary outlay.

Sealed Gel Cell

Sealed gel cell energy cells share an affinity with AGM prototypes, relying on a denser gel electrolyte solution, facilitating prompt recharging and affording superior performance even in the throes of extreme temperature conditions. These energy cells boast the potential for an operational span of up to a decade before necessitating a substitution. However, the advanced characteristics often equate to an escalated initial investment.

Each genre of solar energy accumulator espouses its unique virtues and defects, underscoring the indispensability of deliberating upon individual requisites and preferences when contemplating the most appropriate selection for one’s solar energy storage infrastructure.

How to Read Battery Specifications

The specifications of the Full PHI 3.8 Solar Battery provide valuable insights. The number in the battery’s name signifies its maximum rated capacity under optimal conditions with a 100% depth of discharge. To determine the actual battery capacity, you need to examine certain fundamental battery characteristics, which can be found in the specification sheet.

Capacity: This indicates the amount of energy a single battery can store. Typically, battery capacity is measured in ampere-hours (Ah), although some manufacturers provide it in watt-hours (WH) for convenience. This allows for easier comparisons between your energy requirements and the battery’s capacity. If the capacity is listed in Ah, you can convert it to Wh using the formula:

size of battery (Ah) * nominal voltage (V) = capacity of a battery (Wh)

Power Rating: This measurement indicates the amount of electricity drawn from the battery to power your electrical devices, typically measured in kilowatts (kW). A battery with high capacity but a low power rating provides a limited amount of electricity over an extended period, suitable for powering only a few devices. Conversely, a battery with low capacity but a high power rating can run your entire home for a shorter duration.

Depth of Discharge (DoD): This parameter reveals how much a battery can be discharged without sustaining damage. For example, suppose you have a solar battery with a 10 kWh capacity and a recommended DoD of 80%. In that case, you should use at most 8 kWh before recharging the battery.

Round-Trip Efficiency: This metric quantifies the energy lost while storing it. Higher round-trip efficiency values signify less energy loss.

Calculating the Number of Batteries

Solar panels are typically paired with battery banks to provide uninterrupted power during periods of low sunlight. Here are some key factors for how many batteries to power a house you’ll need:

Number of Batteries: A standard battery bank that provides around 90 kilowatt-hours of electricity can sustain an average American household for approximately three days. For generating 2.4 kilowatts of electricity, you’d require a battery bank comprising 38 batteries. However, this number may vary based on the power produced and consumed.

Power Consumption Rate: Understanding how your household consumes energy is vital. For reference, 1 kilowatt-hour is equivalent to 1 hour of 1 kilowatt or 10 hours of a device with 100 watts. If your monthly energy consumption is 901 kilowatt-hours, it translates to an hourly consumption of 30 kilowatt-hours.

Battery Specifications: Battery capacity is determined by voltage and ampere-hours. For instance, a 400-amp-hour battery can deliver 4 amperes for 100 hours. The battery’s ampere-hours are then used to calculate capacity in kilowatt-hours, which is essential when determining the number of solar panels and batteries required for your home.

Desired Backup Duration: The time you want your solar panels to provide backup power is another critical consideration. Solar panels rely on stored energy from the battery bank during limited sunlight. However, this energy source is finite and will be depleted without a primary energy supply or sufficient sunlight to recharge the batteries.

Calculating Battery Requirements

For Off-Grid Systems (10 Batteries)


Off-grid systems, disconnected from the grid, rely entirely on batteries. More batteries are better to ensure uninterrupted power for your battery-powered home when solar energy is unavailable.

Key battery characteristics to consider are capacity, DoD, and round-trip efficiency. When multiplied, they yield the real battery capacity. For a PHI 3.8 battery:

3.8 kWh * 80% * 98% = 2.98 kWh

Assuming an average American house consumes about 30 kWh daily, your house batteries should provide this amount for a one-day emergency backup. For the PHI 3.8 battery, you’d need at least 10 of them:

30 kWh ÷ 2.98 kWh ≈ 10 PHI 3.8 batteries

For Hybrid Systems (7 Batteries)

Hybrid systems are connected to the grid but incorporate battery storage as a backup. This backup is smaller than an off-grid battery bank and is used when solar energy is insufficient or the grid is down.

Considering that your home consumes about 30% of its daily energy during the day while you’re at work. For the remaining 70% at night, the solar panel system’s task is to generate and store the daytime 70%. With a daily energy consumption of 30 kWh, you’d require a 21 kWh battery array, which can be achieved with 7 PHI 3.8 batteries:

21 kWh ÷ 2.98 kWh ≈ 7 PHI 3.8 batteries

For Grid-Tied Systems (2 Batteries)


You can incorporate solar batteries into a grid-tied system as an emergency backup for critical loads, such as medical devices, a fridge, a space heater, and lighting, that must remain operational during grid failures.

To size your battery bank, list your critical loads and determine their peak power requirements – the maximum energy consumption at any moment. For example:

Critical Load

Max. Running Wattage

Surge Wattage

Peak Power Requirement

6 * 60 W Light Bulbs

360 W

360 W


200 W

1,100 W

1,300 W

Laptop Charger

60 W

60 W


620 W

1,100 W

1,720 W

Summing these values gives a total peak power requirement of approximately 1.7 kW, the maximum discharge rate your battery should support. PHI 3.8 batteries have a power rating of 1.15 kW, so you’d need at least two of them to endure power outages:

1.7 kW ÷ 1.15 kW ≈ 2 batteries

Two PHI 3.8 batteries can power critical loads for approximately 5 hours. To calculate this, divide the battery’s real capacity by the total running wattage from the list:

2,980 Wh ÷ 620 W ≈ 5 hours

Choosing the Right Solar Battery: Quick Tips

Selecting the perfect solar battery installation is crucial for your energy needs. Here are some brief guidelines:

  • Power Rating: Need more power? Pick a high-power solar battery.
  • Instantaneous Power: For energy-hungry appliances, go for high instantaneous power.
  • Usable Capacity: Powering your home long-term? Choose a higher usable capacity.
  • Efficiency: Maximize every kilowatt-hour with higher round-trip efficiency.
  • Battery Type: Opt for lithium-ion NMC for power and space efficiency.
  • Longevity: Consider lithium iron phosphate (LFP) for a long-lasting solution.
  • Safety: Prioritize safety with an LFP solar battery.
  • Off-Grid: To go off-grid, ensure your battery matches your home’s usage and consider a backup generator.

These quick tips will help you find the perfect solar battery. Read How many solar panels do I need to power a house to explore more options.

Final Thoughts

Optimizing your solar power generation involves thoroughly analyzing your region’s sunlight hours, your home’s power consumption patterns, and the specifications of the batteries you plan to use. By carefully evaluating these factors, you can design a solar energy system that meets your energy needs efficiently and sustainably. Solar Earth Inc provides all types of solar panel systems if you need any queries please call us @(805)691-8000.