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What You Need to Know About an Off-Grid Solar-Powered System

Jessica PirroDecember 26, 20194700

The notation of getting an off-grid solar-powered system is becoming more and more popular. Due to the fact the cost of electricity is rising throughout the country, it’s hard to not at least consider cutting the cord each time a utility bill is delivered. But one thing that a lot of customers don’t understand is, what it means to go off-the-grid.

Everything You Need to Know About An Off-Grid Solar-Powered System

What Does it Mean to go Off-Grid

Going off-grid in terms of electricity means completely removing any connection to the larger electric grid, which powers the large majority of homes buildings and businesses through the country. Meaning that to go off-grid you will need to meet all of your home's energy needs with electricity that is produced on-site.

It is also important to note installing solar panels on your rooftop does not mean that you have gone off-grid. The majority of the solar-powered systems that are on the market are not designed to generate solar power, consistently enough to be your home's only power source. Thus, most homeowners with a solar-powered system are still connected to the grid.

If your home is still connected to the grid, you can use net metering, which allows you to sell the excess solar power, being generated by your solar-powered back to the grid. Then when your solar-powered system isn’t producing solar power, you can draw energy from the grid to power your home.

When you have an off-grid solar-powered system, you won’t have access to the larger electric grid when you need it, either at night when your solar panels aren’t producing any power or in the event of a storm. So instead of drawing power from the grid, you would instead create your own personal “grid”, installing on-site battery storage to store the excess solar power from your solar panels for use at a later point in time.

Calculating the Cost of Solar For an Off-Grid Solar-Powered System

When you get an off-grid solar-powered system, a lot more is going to go into it than simply installing solar panels and disconnecting from the utility. There are four key steps to determining if going off-grid will be feasible for your home, and how much it is going to cost:

- Calculate home much electricity you use.

- Determine how many solar power batteries you will need.

- Design a solar-powered system that you will need.

- Add up the cost of solar.

How Much Electricity Do You Use?

The first step in going off-grid is going to be how much electricity you use, alternatively known as your consumption or your electricity load. To figure out how many batteries for solar power and solar panels you will need to go off-grid, you will need to figure out how much electricity you will use.

Electricity Consumption Estimations:

Appliances

Estimated Annual Load (KWH)

Estimated Daily Load (KWH)

Refrigerator

600

1.6

Air Conditioning Unit

215

0.6

Central Air Conditioning

1,000

2.7

Space Heater

600

1.6

How Many Batteries for Solar Power?

To go off-grid, you are going to need a way to store the excess solar power that is produced by the solar-powered system at the times when you are not using it. Most importantly, not every solar power battery can operate independently of the grid, even if you’re feeding it solar energy. To go off-grid, you specifically need a battery that can “island”, or form its grid, so that the solar panels will recharge the battery every day without a grid connection.

To determine the number of these batteries you need to power your house for a single day, you need to know both your daily electricity consumption and the amount of electricity stored in a standard solar power battery.

The amount of solar power that is stored in a battery is going to be called the “Usable Energy”, expressed in kWh. This is the amount of electricity that you can get out of a battery, after accounting for electrical losses and any energy needed to power the battery itself.

The average American household uses around 30 kWh a day. Given the conversion losses that are associated with storing solar power from the solar panels, you will need enough batteries to store slightly more than what you use per day, likely close to 32 kWh, depending upon the efficiency of the battery you select.

It’s important to remember that this is only the number of batteries you will need to power your house for a single day. You are going to want to have enough backup storage capacity to power your home for many days, or perhaps even an entire week. To ensure you still have electricity if you have a period of inclement weather or need to use more than your average daily usage in a single day.

How Many Solar Panels Will You Need?

The next step is going to be designing your solar-powered system to your property and storage setup yo be large enough to fill your battery daily,

The solar power that your solar-powered system produces is directly a result of the amount of sunlight that your solar panels receive. The average home in the U.S. is going to receive an average of sun hours a day, over a year, that represents not the amount of time solar panels are in the sun but rather measures the number of hours during which sunlight intensity is 1,000 W/square meter. The amount of solar power that your solar panels are going to be produced is also related to the angle that they are installed at and whether they receive direct sunlight all day, or are affected by the shade.

To determine how many solar panels that you are going to need to fill your batteries every day, divide the amount of electricity needed (in this case, 32 kWh) by the number of expected sun hours (5 hours in this example):

32 kWh/5 hours = 6.4 kW

Based on this example, you would need a solar-powered system about 6.4 kilowatts to fill up a battery bank with a capacity of 32 kWh per day.

The number of solar panels that you’ll need for a 6.4 kW solar-powered system depends on the solar power output of the same panels you use, which will generally range in wattage from 250W to 400W:

Solar Panel Wattage (W)

Number of Solar Panels for a 6.4 KW Solar-Powered System

250

26

300

21

350

18

400

16

Why Go Off-Grid?

Some homes function very well off-grid with smaller and less expensive solar panels and storage systems. These homes are designed specifically for this purpose, often because they are located in remote areas and don’t have access to an electricity grid. Some of these houses are built to Passive House standards and require very minimal energy for heating or cooling. In a lot of cases, the desire to install an off-grid solar-powered system is going to be less about cutting the cord with your utility and driven by improving resiliency.

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