How Many Solar Panels Do I Need For 1000 kWh Per Month?
Solar energy can help us lower Carbon Dioxide (CO2) emissions, it "just" has to be collected in the most efficient way possible in order to lower expenses, and to make the installation of solar panels and the required electronics as compact and easy as possible.
The collection of 1000 kWh per month using solar panels is not an easy task, but it can be done with sufficient solar panel surface and a few more important components.
Published: April 9, 2022.
Last Thing First: What To Do With 1000 kWh Per Month
When trying to collect 1000 kWh per month, the first thing to do is to decide what should one do with that energy - transfer it to the power grid immediately or store it into the deep cycle batteries, preferably lithium batteries, and release it later.
Transferring The Collected Energy To The Power Grid
If one wants to collect energy and transfer it immediately to the power grid, then one needs 1000 kWh per month of energy "behind" charge controller that transfers the energy.
Since such charge controller also manages solar panels, its energy efficiency is of utmost importance and ranges from 80% to up to 90+%.
If we use a charge controller with an energy efficiency of 85%, that means that solar panels must provide:
E (kWh) = 1000 kWh / 0.85 = ~1176 kWh
per month to the charge controller which dissipates ~176 kWh of energy per month as heat.
In order to collect 1176 kWh per month, one has to collect:
Eday (kWh) = 1176 / 30 = 39.2 kWh
39.2 kWh per day.
In order to collect 39.2 kWh per day during 12h of daylight, one has to collect:
P (kW) = 39.2 kWh / 12h = ~3.3 kW
~3.3 kW of solar energy from the solar panels to their charge controller.
Note: 12h of daylight is not always possible to achieve because of the season, weather, and other potential issues.
Also, we must emphasize that this ~3.3 kW of energy is the energy that solar panels effectively provide to their charge controller/electronics. In real-life, solar panels' efficiency on average ranges from 40-80%, sometimes even more.
So, if we assume 66.6% solar panel efficiency, in order to provide ~3.3 kW of energy to the electronics, one needs:
Psolar panels (kW) = 3.3 / 0.666 = ~5 kW
In order to make a 5 kW solar panel installation, one needs, for example:
- fifty 100W solar panels, or
- twenty-five 200W solar panels, or
- ten 500W solar panels, etc.,
with mounting hardware and the electronics to make such system work - plus paperwork to be allowed to legally transfer energy to the power grid and earn money by doing so ...
Storing The Collected Energy Into the Batteries and Releasing It Later
Releasing the energy stored in the lithium batteries later, when the sun is gone, can be a tempting goal since energy prices vary during the day.
Anyway, if we want to transfer the energy from the lithium batteries into the power grid, we have to calculate all the energy losses during such process.
In order to transfer 1000 kWh of solar energy collected in the high-capacity, high-efficiency lithium batteries, one has to calculate energy losses in the power inverter and the rest of the electronics, which is on average again around 85%.
E (kWh) = 1000 kWh / 0.85 = ~1176 kWh
So, batteries have to transfer 1176 kWh of energy to the controller for it to be able to transfer 1000 kWh of energy to the grid.
Since lithium batteries are not ideal batteries (but they are far better for tasks like this than lead-acid batteries), with their energy efficiency of around 90%, the batteries must be recharged with:
E (kWh) = 1176 kWh / 0.90 = ~1306 kWh
1306 kWh of energy per month.
In order to generate 1306 kWh per month to charge the batteries, one has to take into the account the energy efficiency of the solar battery charge controller, which is on average 85%:
E (kWh) = 1306 kWh / 0.85 = 1536 kWh
In order to collect 1536 kWh per month, one has to collect:
Eday (kWh) = 1536 / 30 = ~51.2 kWh
51.2 kWh per day.
In order to collect 51.2 kWh per day during 12h of daylight, one has to collect:
P (kW) = 51.2 kWh / 12h = ~4.27 kW
~4.27 kW of solar energy from the solar panels to their charge controller.
If we assume 66.6% solar panel efficiency, in order to provide ~4.27 kW of energy to the electronics, one needs:
Psolar panels (kW) = 4.27 / 0.666 = ~6.4 kW
In order to make a 6.4 kW solar panel installation, one needs, for example:
- sixty-four 100W solar panels, or
- thirty-two 200W solar panels, or
- thirteen 500W solar panels, etc.,
with mounting hardware, all of the required electronics, and deep cycle lithium batteries to make such system work - plus paperwork to be allowed to legally transfer energy to the power grid and earn money by doing so ...
As one can see, the difference between these two examples is that in the second example, one needs ~28% more solar panels, plus more complex electronics and a large lithium battery bank that is able to store at least 39.2 kWh of energy in the period of 12h.
How To Make 39.2 kWh Lithium Battery Bank?
For people who want to collect 1000 kWh (effectively) per month and want to store 1176 kWh per month (39.2 kWh per day) in the battery bank (second example in this article), a large lithium battery bank is needed.
But, it can be created relatively easily using off-the-shelf deep cycle lithium batteries, for example, Ampere Time 12V 300Ah lithium battery.
Ampere Time 12V 300Ah Lithium Iron Phosphate (LiFePO4) battery is able to effectively store at least 3600 Wh and it supports connections in series in parallel up to 4S4P (16 batteries in total).
Thus, if one connects 12 Ampere Time 12V 300Ah lithium batteries in 3S4P (3 in series, 4 in parallel - 36V 1200Ah) or 4S3P (4 in series, 3 in parallel - 48V 900Ah), one creates a lithium battery pack that is able to store at least 43.2 kWh of energy.
And no, such battery pack is not cheap and neither is the rest of the required gear.
For more about deep cycle lithium batteries feel free to check our What Is The Best 12 Volt Lithium Battery article.
Few Final Words
Collecting and transferring 1000 kWh of energy is not an easy task and the required equipment is not cheap, especially if the energy is not transferred to the power grid directly.
Deep cycle lithium batteries support 8-10x more charging/discharging cycles than lead-acid batteries and are a far better choice than lead-acid batteries.
When calculating the number of solar panels we assumed average values for the energy efficiency of various components - increasing their efficiency can be expensive, but in the long run, it can be worth it.
If You plan on making a 1000 kWh per month solar plant, use the information found in this article only as a guideline, not as a blueprint.
And whatever You do, it is your own responsibility... Stay safe!