How Many Batteries Do I Need For a 10kw Solar System?

A 10kw solar system is enough to meet the power needs of a large house. It is the ideal solution if you want to live off the grid and be fully independent from the power companies. But how many batteries will you need?

A 10kw solar system that produces 40kwh a day needs 6 x 300ah 24V batteries to store all the energy produced. Divide the daily solar array watt output by the battery voltage and you have the minimum battery capacity required.

Calculate 10kw Solar System Battery Requirements

Figuring out solar battery requirements is a bit complex because the needs vary from one household to another. What follows is a simplified process.

Total solar array output / battery voltage = battery amps required

A 10kw solar system produces 40kw a day, or 40,000 watts. Divide the wattage by the battery voltage and you have the answer. Batteries come in different voltages but we will use 48V as it is the most practical for large PV systems.

40000 / 48 = 833.3

You need a 48V battery bank with at least 833 amps. For instance, you can buy 3 x 300ah 48V batteries, 4 x 200ah, 2 x 450ah, any combination as long as it is at least 833ah.

You can use 24V or 12V batteries of course. Connect them in a series to increase the voltage so it can handle the system output. The only drawback is you have to double the number of batteries required.

If you use 24V batteries, you will need 1666 amps. The best option would be a 24V 300ah capacity like the Shunbin LiFePO4 Battery as it can handle the power. You will need 6 of these for a 10kw solar sytem.

If you need 3 x 300ah for 48V batteries, you will need 6 of these for 24V batteries and a dozen for 12V. Batteries take up a lot of space and are heavy. More of them also means more wiring required which adds up to the cost.

How Many Batteries Do You Really Need?

The calculations given above are straightforward enough. But it assumes that you want to store all the power your 10kw system produces in a day.

If you only want to store the excess solar energy produced, subtract the extra amount from the total output.

Example: if you use 30kw a day and the system produces 40kw:

40kw-30kw = 10kw

10kw = 10000 watts

You need a battery bank that can hold 10000 watts.

10000 / 48 = 208ah
10000 / 24 = 416ah
10000 / 12 = 833ah

As usual you have to round off to the nearest battery size available. You could get 3 x 100ah 48V batteries, 2 x 250 24V batteries or 3 x 300 2V batteries.

10kw Solar System Battery Backup Power Calculation

Here is another example. Suppose you want to store enough power to last for three days, just in case there is a power failure or winter storm.

If your daily consumption is 30kw, you would need 90kw to cover three days’ use.

90kw = 90000 watts

90000 watts / 48V = 1875ah
90000 watts / 24V = 2750ah
90000 watts / 12V = 7500ah

To meet your daily power consumption over three days, you need about 5 x 400ah 48V batteries. You can use these same steps to calculate how many batteries you will need over a specific period.

Note that these calculations will fill the batteries to their capacity. If this is what you plan to do, understanding discharge rates becomes essential.

Battery Discharge Rate and Capacity

If you only want to store the reserve energy, the capacities given above will be enough. But if you end up using the excess energy, the battery discharge becomes important.

Suppose you have 3 x 100 48V batteries to store the extra power produced by your system, anywhere from 10kw to 12kw a day.

If you end up using all the energy, it will fully discharge the battery. Batteries have different discharge rates , but most FLA should not be discharged below the halfway point.

Only lithium ion batteries can be fully discharged. If you have FLA batteries and end up discharging them completely, you have to double the capacity.

If your household consumes 30kw a day and your system produces exactly that amount, you do not need any batteries. But there are days when you consume less and times when you use up more.

That is where battery storage comes into play. If you consume 30kw daily and the system generates 40kw, you don’t want to waste the extra power.

If you are on the grid, that extra power goes into the power company where you can access it anytime. But if you are off grid you need a battery bank for storage.

How Much Power Does a 10kw Solar System Produce?

In a perfect world, a 10kw solar system will produce 10kw a day and 1000kw a month. But there are several factors that affect output, the most important being the number of sunlight hours available in your location.

A 10kw solar system in Los Angeles might generate 15% more power than a similar 10kw system in Seattle because there is more sunlight available.

• A 10kw PV system in Phoenix, Las Vegas, Austin or Los Angeles can yield 40 to 48kw a day.
• The same system however, will only produce 33 to 35kw in New York, Cleveland and Boston.
• In some parts of the Northeast the output will be less than 30kw.

Bear in mind these are only the typical output you can expect. Other factors like the solar panel quality, orientation, efficiency etc. will affect performance.

Is a 10kw Solar System Enough to Power a House?

The typical American home uses 900kw a month, so a 10kw system should be enough. Assuming 5 hours of sunlight a day, this system can produce 30kw to 40kw or more than 1000kw a month.

Of course you need to consider the factors stated earlier. Some states have more sunlight than others so the output will vary. The average consumption is also just that, the average. What you actually consume may be much higher or lower than the average.

To find out if a 10kw solar system is enough for you, we suggest the following:

• Check your monthly consumption. It will be on your monthly bill. Average it out over 12 months.
• Determine how many sun hours are available in your location.
• Compare different types of 10kw solar system kits.
• Calculate how many batteries you will need. This will depend on how many sun hours are available and how often you plan to use battery power.

Once you have this figured out, you can contact the solar kit manufacturer. inform them of your plans and that you plan to install a battery bank as well. They might offer more suggestions on what battery sizes to use.

The size of the house has no bearing on the power consumption. An average sized house that uses a lot of appliances will consume more power than a large house that is more energy efficient.

How Much Power Does a 10kw Solar System Cost?

A 10kw solar system costs $28,000 on average, with the range from $21,500 to $35,000. However the actual price will depend on your location and the tax credit discount..

10kw solar system kits are now available. The package contains all the components needed to install a solar system. A standard kit may include:

• Solar panels: the number depends on the watt size. Usually a 10kw system has 27 to 35 soar panels.
• Mounting and racking hardware
• Inverter
• System monitor
• Financial report: this tells you how long it will take to recoup your investment

The batteries are not included. Neither are the charge controllers , wires, cables, junction boxes and fuses.

Installation fees are separate as well. If you are knowledgeable with electronics and do not mind going up your rooftop, you can install the system and save on costs.

The price differences can be significant, in particular with the installation. You should do some research first and compare as many of them as possible. This takes time, but you could save thousands of dollars in the process. It is well worth the effort.

Conclusion

A 10kw solar system is a major investment, and a life changing one. If you want to buy this system, plan ahead. By using the information given here, you can decide how many batteries you will need and what other components are required.