The inefficiency of wind generators due to no wind and snow-covered solar plates have greatly promoted the use of home batteries. You can use the battery bank at home to power almost your all house appliances even during power outages.
Undoubtedly, a home battery backup system is quite expensive, so you should know the exact number of batteries needed to power your house to secure your budget. Hence, the main query is how would you know the number of batteries needed to power your home?
Well, here we got you! In this article, we have discussed some factors that will help you out in making a better decision. Also, you’ll come to know about the method of calculating the number of batteries and the amount of energy your house consumes.
So, let’s move in-depth for finding the answer to your question!
Related Article: What Are the Best Home Battery Backup Systems of 2022
Basic Battery Characteristics
The following are some basic properties of batteries that determines the efficiency of the battery. You must consider these factors whenever going to buy a battery for you. They’ll surely benefit you in making a great choice.
Capacity
The battery capacity indicates the maximum amount of electricity produced as a result of electrochemical reactions taking palace in a battery. It is typically measured in ampere-hour (Ah). For instance, a battery rated 500Ah has the ability to provide 500 A in one hour, in ideal situations.
Moreover, you can experimentally measure the capacity of a battery by calculating the time taken for it to discharge at a constant current. By putting the values of discharge current and discharge duration in the below equation, you can easily determine the capacity of a specific battery;
Capacity (Ah) = Current(A) × Time(h)
However, the following are some factors that may influence the capacity;
● Temperature
With the increase in electrolyte temperature, the capacity of the battery also increases. Yet, it’s not a wise decision to intentionally elevate the temperature, as it may lower the battery lifetime.
● Charging and Discharging Rate
Normally, if the discharge rate of the battery is increased, the extraction of energy amount decreases, thus lowering the capacity of the battery.
● Age of Battery
As the battery gets older, the capacity decreases due to pouring the active substance from the plates.
● The Density of the Electrolyte
Generally, if you put a high-density electrolyte in the battery, consequently capacity increases. However, high-density results in a shorter lifespan of the battery, hence it’s not favorable to increase it according to your desire.
Power Rating
The total amount of electricity you can consume from the battery to power the appliances is known as the power rating. Usually, you can measure the power rating in kilowatts (kW). A battery with a high capacity but low power rating is not beneficial to you because it offers less energy for a long period.
As a result, you can only power a few electrical devices in your home. Whereas, the battery featuring low capacity and higher power rating is ideal for running your whole home appliances, yet unfortunately not for long periods.
You may measure the power rating of a battery by multiplying the battery voltage by the number of Amps. Let’s take an example! A 15-volt battery having the capacity of 100Ah has a power rating, 1500Wh, i.e, 15 × 100.
Furthermore, you should consider two factors regarding power rating;
Instantaneous Power
If you need to run an appliance that requires an extra surge of power, then instantaneous power is most suitable. For example, a pump needs a lot of power when it is turned on, afterwards the power requirements drop.
Continuous Power
If you want to power several circuits and appliances continuously, continuous power will work best. Typically, the batteries feature 5 and 8 kilowatts of continuous power rating.
Depth of Discharge (DoD)
Depth of discharge refers to the amount of energy that has been discharged from the overall capacity of the battery. It is represented by the percentage. You might find this concept complex, though it’s pretty simple. Let’s suppose you consume 40% of the power from your battery, which means the battery has a 40% depth of discharge, while 60% of its capacity is remaining.
You can calculate the depth of discharge by putting the values in the following equation;
DoD= removed the amount of charge/maximum available amount of charge × 100
Typically, the cycle life and depth of discharge are correlated with each other. If a battery is frequently charged and discharged, the number cycle life will automatically decrease. Hence, the lifespan of the battery decreases. Further, you should never fully discharge your battery in order to prevent the life of the battery.
Round Trip Efficiency
The last basic characteristic of a battery is its round trip efficiency which allows you to know the number of electricity units received from the battery for each electricity unit put into it. You may also define this term as the efficiency of your battery and inverter to convert and store electricity. Normally, round trip efficiency is expressed in percentage.
Round trip efficiency can be calculated by using the below equation;
Energy recovered/ Energy input × 100
If the round trip efficiency is higher, less energy is lost because of storage, therefore the whole system is more efficient. Mainly, 80% round trip efficiency is considered ideal for home batteries. It can never be 100% as energy losses will always be taking place.
What Factors Impact Your Home Battery System Sizing?
When deciding the number of batteries needed to run your home, there are certain factors that impact the battery sizing. Let’s have a look!
Household Electricity Usage
The most crucial factor is to calculate your household electricity usage per day. If you’re living in a small house with fewer electrical appliances, you’ll definitely need a small-sized battery. On the contrary, a larger house consumes more power.
The ideal way to determine household electricity usage is to detect it from your electricity bill or meter. Mainly, the household appliances include;
● Lights that consume 100W
● The refrigerator needs almost 400W
● The electric stove uses 1000W
● Microwave requires 1500W
● 3 ton HVAC system uses 3500W
You might have got a basic idea of household electricity usage from the above-mentioned measurements.
Size of Your Solar Panel System
When you’re managing your home energy needs through batteries, you would surely need to charge them up. For this purpose, you have to get electricity from a grid or solar panel. The solar panel is a more economical and effective means. Therefore, you may set up solar panels with adequate electricity production.
The size of the solar system you need is determined by the electricity requirement. If you need to charge less number of batteries, you may use a panel of small size with less kW and vice versa.
Moreover, if a house needs 200A to fulfill its power needs, a solar setup with 48kW energy production would be enough. The position of panels on the roof and exposure to the sun also affect this electricity production.
If one system isn’t enough to meet your energy demand, you may install more than one solar panel. An average house may need 20 to 24 panels of 330 watts to meet its entire energy requirements. It would help to get the maximum benefit from this solar energy setup.
Time Period
When you are constructing a battery-powered setup for your home, you must check out the duration that it can manage without an electricity supply. Though, It’s normal to have natural disasters in your surroundings. Your energy system should be reliable enough to survive a few days in case of any cut to the power supply.
Moreover, it’s the number of batteries and their storage capacity that determines the lifespan of your power system. If your battery system constituents 10kW power, it may run up to 10 hours in a power outage.
Similarly, if you need a backup for at least two days you have to arrange a 45 to 50kW battery power system.
Specifications of Battery
Different batteries come with different characters but it’s your choice to go for one with the specifications, you’re looking for. These specifications may include storage capacity, specific voltage, amp-hours, etc.
The number of ampere-hours determines the current delivered by a battery in one hour. For example, a battery with 400 amp-hour may provide 4 amperes current for almost 100 hours. On the other hand, the voltage of the battery generally remains constant but it may start decreasing with the discharging of the battery.
Both these factors would help to determine the power capacity of the battery. All you need to do is to find the product of operating voltage and amp-hour and divide it by 1000 to get capacity in kilowatt-hours. For instance, a battery with 400 amp-hour and 6V specific voltage would store up to 2.4 kilowatt-hours.
Number of Batteries
The number of batteries required to run a house is determined by the energy requirement and size of that house. A house with more appliances and more energy demand would require more batteries as compared to one with less energy usage.
Additionally, the storage capacity of the battery is also pretty crucial in determining the number of batteries. The batteries with more potential provide more energy. If we talk about an average house, it would require almost 90 kilowatt-hours of energy for three days.
If you’re having batteries with a 2.4 kW storage capacity, you would need 38 batteries ideally to manage this battery bank. There can be some shortcomings in batteries. Therefore, you are supposed to arrange more than the calculated number of batteries. Besides, some power is also consumed by the inverter that converts DC to AC to run some household appliances.
How to Calculate the Number of the Batteries Needed for Your House?
Up to this point, you are pretty well aware of the factors that decide the size of your battery. Now, it is time to perform some calculations to determine the exact number of batteries you require to run your house. So, let’s move on!
Energy Needs
The prior step is to know the estimated time you need to power your house using the batteries. Once you are done with this you should calculate the energy needed for running all your home appliances in that estimated time. Here is a table representing a rough estimate of household energy usage;
| The critical load of Appliances | Maximum running wattage | Estimated time for running the appliances |
| Air source heat pump | 3500W | Under 3 hours |
| Television | 300W | 33 hours |
| Refrigerator | 200W | 50 hours |
| Five light bulbs | 5*20W | 100 hours |
| Phone charger | 25W | 400 hours |
| WiFi router | 6W | 1600 hours |
You can easily power the above-mentioned appliances by using a battery with 10kWh usable capacity. Therefore, you may expect to run your phones, computers, wifi, refrigerator, and lights during an outage of almost 24 full hours.
Calculations
It’s time to make some calculations, so be ready.
● Step 1
As you are there with a list of wattage and running time of different appliances, now let’s find out the power rating in Wh. The simple method is to multiply each wattage with the number of hours you need to power the device. However, if the power is not given in watts, you may calculate it by multiplying the current with voltage.
For instance, in the case of a 200W refrigerator which you are supposed to power for 24 hours, the power rating will be, 200*24= 4,800 Wh.
● Step 2
You should be prepared for the long blackouts, so the ideal way is to calculate the backup power in advance. Suppose, you want to run your refrigerator for 3 days, multiply the power calculated in the above step by a number of backup days, i.e, 4,800*3=14,400Wh.
● Step 3
As we know the lower the discharging rate of the battery, the longest will be the battery life. In this step, you need to play with DoD, suppose it is 50%.
I.e, 14,400/0.5 = 28,000 Wh
● Step 4
The next step deals with the temperature. Usually, the batteries show less efficiency at lower temperatures. If your battery needs to work at 21 C, the factor that corresponds to this temperature is 1.04. Hence, we will be multiplying the result of the above step by 1.04, i.e, 28000*1.04 = 29,120Wh.
● Step 5
You are supposed to connect the batteries together, according to the voltage of your electrical system. Generally, if you use the higher voltage, there will reduction in the loss of voltage over extended distances. Therefore, divide the result from the above step by the desired voltage, i.e, 48 V.
E.g. 29,120 / 48 = 606Ah
● Step 6
Finally, it’s time to determine the number of batteries you need to power.
E.g, consider a 140 Ah (12V) home battery for a 600 Ah 48V battery;
48=600/140 * 3= 13 batteries
That’s all about calculating the number of whole house battery banks for your home. We have just calculated for one appliance, but you may go for all of them by following the same method.
Related Article: How Long Will a 10kWh Home Battery Last During an Outage?
Is ETEKWARE Home Batteries Right for Me?
For sure, ETEKWARE home batteries are perfect to meet your household energy demands during power outages. They possess remarkable features that make them stand alone among most batteries. Typically, ETEKWARE offers four different home power system models;
● Home wall-mounted battery
● Home wall-mounted battery (Authorized Design)
● Powerwall energy battery
● Powerwall energy battery (Authorized Design)
All these batteries consist of lithium iron phosphate cells and each module features a smart independent BMS system. The long lifespan, high storage capacity, and high efficiency will surely let you enjoy the performance of ETEKWARE home batteries during blackouts.
Moreover, its standard compact size and design make them easily portable. Plus, they are well known for their high energy density. On top of that, ETEKWARE offers more than 6000 cycles with 80% Depth of Discharge which is enough for proving their durability and longevity.
Final Words
Hopefully, this article will benefit you in making perfect calculations for determining the number of batteries needed to power your house. You may follow the above-given example to calculate the energy needs of your whole house.
Yet, the number of batteries entirely depends upon the energy needs of your house. The more appliances you will run the more batteries you will need. Moreover, you may consider ETEKWARE home batteries to power your house, as they provide remarkable performance during power outages.
