Off-grid Solar Power Systems: Do Need a Utility Company to Survive?
What it Takes to Go Off-Grid, Including Pros and Cons
Off-grid systems make the most sense for homes that don't have electricity yet, many of which are located in rural areas. Extending power lines to these homes can cost anywhere from $15,000 and $50,000 per additional mile, which makes adding the additional equipment needed for an off-grid system a cost-effective option. Both off-grid and grid-tied systems have their pros and cons. Homeowners considering an off-grid solar array need to determine which factors matter most to them.
Pros of Off-Grid Solar
- Power the home without help from the power company (no power bills).
- Continue to generate electricity during power outages.
Off-grid Solar Cons
- If the solar array malfunctions, there isn't an easy backup energy source (without battery backup).
- If poor weather persists over several consecutive days, battery backup may not charge enough to continue powering the home.
Pros of Grid-tied Solar
- The utility provides energy when the solar array can't. (during poor weather and at night).
- Solar homes with battery backup can use the grid as an alternative energy source.
Cons of Grid-tied Solar
- Utilities charge more for power pulled off the grid than they pay for excess solar energy put onto it. (1:1 net metering programs are an exception).
- Homeowners pay a connection fee, $10-$20 per month, regardless of whether they pull electricity off the grid.
How do Solar Array Components Work?
Regardless of whether you're grid-tied, all solar arrays essentially have the same components. Both grid-tied and off-grid solar can leverage the benefits of battery backup, and they all need an inverter, racking system, and solar panels to function. The main difference between these two solar installation types comes from the number of components needed to run the solar array. Due to net metering, grid-tied solar arrays often rely, at least partially, on the grid. This means the solar arrays don't need to produce as much excess power during the day to meet the homeowner's needs throughout the year. However, homes with off-grid solar arrays need to produce enough electricity to continuously meet their home's energy needs. Larger systems not only cost more to install, but they also take up more roof and potential ground mount/backyard installation space. Homeowners considering off-grid solar need to determine whether they have enough space for the modules. Let's review how many more panels an average solar array would need if off-grid. As of 2019, the EIA reported that the average home in 2018 uses 10,972 kWh per year, which is equivalent to 914 kWh per month.
Number of Solar Panels Needed
Residential solar panels typically produce between 200 and 300 watts of electricity. Depending on the location of the home and the direction of the available space, a home that consumes 11,000 kWh per year would need between 28 – 34 solar panels. The average residential solar panel takes up about 15 square feet, which means this system would need between 420 and 510 square feet of non-shaded non-north-facing space. Homes with limited space may not fit this large of a system, making them a better fit for grid-tied solar.
The Part Inverters Play
An inverter converts the direct current produced by the solar panels to alternating current, making the power usable. The number and size of inverters needed increases with the size of the system. Given an inverter's function, installers match the inverter's wattage rating to the projected wattage of the system.
Battery Backup and Charge Controllers
Batteries allow homeowners to store their excess power. Charge controllers make sure that the battery doesn't overcharge. Some battery backup options have charge controllers in them. Due to the NEC 2017, everyone purchasing solar should consider adding some form of battery backup. As of 2019, solar homes now have to shut off power at the modular level during power outages. All homes without battery backup will not have access to electricity. To power a typical home, an off-grid solar array needs anywhere from 8 to 14 Powerwalls. However, grid-tied homeowners may not want that much storage since they have the utility company as a backup energy production method. Go Solar Group realizes this and offers a selection of different battery backup package sizes for off-grid systems.
Solar Panel Racking, Conduit, Wiring, and Balance of System (BoS)
While not often mentioned, the wiring and racking system for the solar array also plays a part in the cost and complexity of the project. The type of wiring and racking needed depends on the type of solar installation. The balance of system also factors in the structural needs of the installation itself.
Find out why our solar arrays stand out among the rest at our panels comparison page.
How Useful are Off-grid Solar Calculators?
Those who are not sure about whether solar is right for them often turn to solar calculators to determine how much solar modules can save them. However, if looking into an off-grid system, they have more factors to consider, like how much it would cost to run power lines to their home and adding on the local electricity rate over the life of the array to find the comparative cost of solar. Individuals who live far away from the grid should consider off-grid solar. Homeowners already connected to the power grid should note that going off-grid won't save them as much money. These individuals need to look at their priorities, options and goals. While most homeowners can add solar and battery backup, the amount they need to power a home without the grid may not be viable for them.
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