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What Size Generator Do I Need?

Posted 4/30/21 | Filed under Solar Education | Comments (0)

Determining which solar generator will be best suited for your needs can be rather daunting. Each day we receive countless phone calls from people who are interested in picking up a solar generator but have no idea where to start.

Today, we are going to identify the most important things to look for when choosing a Solar Generator or Battery Backup system. Here we go!

AC Inverter Specifications

One of the first things you should look at when choosing the best solar generator for your application is the Inverter information. The inverter is a very important piece of the puzzle, that converts the power stored in the generator from DC to AC power. Understanding this process is not essential, however, you should review your power requirements and ensure that the inverter found in the solar system you are purchasing, can handle the continuous output of your needs.

For example: Scott needs a generator that can power (4) LED lights that consume 25 watts per light.

Simply multiply the wattage of the lights by the number of items you are powering (25 watts x 4 led lights = 100 watts).

Therefore, scott needs an inverter that can output a minimum of 100 watts continuous.

Battery Size Requirement

The second specification you should be reviewing before making any decisions is the battery storage size. This is the most crucial piece of information when choosing the best solar generator. You will not only need enough energy to power your items for the required time frame; but you will need enough power to sustain your system until you can receive your next recharge, which may be for quite some time depending on sunlight availability and access to power input sources.

Let’s take a look a real time example:

Frank wants to power his CPAP machine for 8 hours each night.

His CPAP machine draws 50 watts per hour.

Therefore, we need to multiply the watt consumption by the required run time (50 watts x 8 hours = 400 watts).

That means we need 400 watt hours of storage capacity right? WRONG. As per general battery maintenance techniques, you want to keep your battery above 50% to extend the lifespan.

Therefore, we need to take our 400 watt hours and multiply it by 2 (400 Wh x 2 = 800 Wh). This will ensure that after our full run time we still have enough power to stay around the 50% charge threshold.

Solar Panel Sizing

The 3rd and final feature you should be reviewing before making any decisions is the Solar Panel/Sizing requirement. While you can simply use your PowerStation as a battery backup, if you require off grid recharging like most folks do, you will want to determine the optimal solar panels for your needs.

The math behind solar panels is a little more complicated due to panel efficiency and line loss. You must also factor in how quickly you will need the system to recharge based on your location and access to direct sunlight.

Chris has a 12V pump that draws 400 watts per hour. That pump needs to run for 3 hours during the day and 2 hours at night.

First, we convert watts to amps by dividing the voltage of the item into the watt draw (400W / 12V = 33.33A).

Then we calculate our amp draw for the day and night (33.33A x 3 hours = 100A for day) (33.33A x 2 hours = 67A for night).

We add those two up (100A + 67A = 167 Amps that we need to recoup via solar).

We then divide our amp deficit by the number of hours we need to recharge in, let’s say 8 hours of sunlight. (167A / 8 hours = 20.87A per hour).

We then multiply the hourly amp requirement by 12V to convert to watts (20.87A x 12V = 251W).

Lastly, we take our calculated hourly wattage and divide it by 0.75 to calculate for line loss/PV efficiency (251W / .75 = 335 Watt solar panel).

The outcome of this math essentially tells us that in order to recharge our system to full in 8 hours of sunlight, we will require a total of 335 watts of solar panels.

Feel free to utilize this guide as a rule of thumb when searching for the best solar generator for you. The three most important things to review are the 1. The Inverter 2. The Battery/Storage Capacity Size 3. The Solar Panel Wattage Requirements.

If you have any questions or comments, please leave them in the section below. We are happy to review your personal use requirements and recommend the best solar generator for you. Please contact us via Email, Chat or Phone, as we are always available and happy to lend our expertise. As always, we are just a phone call away (877-548-3387) and are happy to offer our expertise on all of your Solar Generator needs!
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