Going “off-grid” means disconnecting your home from the national power grid and becoming self-sufficient for your electricity needs. This typically involves installing a renewable energy system, like solar panels, to generate your own power. The solar panels convert sunlight into electricity that can then be used to power your home.
To live fully off-grid, you’ll need batteries to store excess electricity generated during the daytime so that you have power at night when the sun isn’t shining. Having battery storage is crucial for relying 100% on your own solar power system. Many off-grid homes also have backup generators for times when solar panel output is low, such as long stretches of cloudy weather.
The benefit of living off-grid is that you don’t have an electricity bill each month and have greater energy independence. The upfront cost of installing a solar power system can be high, but over time you recoup that investment. Going off-grid requires lifestyle adjustments to limit electricity usage, as you only have as much power as your solar panels can produce. But for many seeking a sustainable and eco-friendly lifestyle, the benefits of off-grid solar living outweigh the costs.
Determining Number of Solar Panels
Going off-grid with solar power requires installing a system that can generate enough electricity to meet your needs. The number of solar panels needed depends on several key factors:
- Electricity Usage – The amount of electricity you use daily/monthly determines the size of the solar system required. Analyze past electric bills to calculate average usage. Account for future needs like electric vehicles. The more appliances and devices used, the more panels needed.
- Roof Space – Panels require adequate unshaded south-facing roof area. Most homes have enough roof space for a solar array that can offset a majority of electrical usage. However, limited roof space may restrict the number of panels.
- Sunlight Hours – The solar potential of a location depends on annual peak sunlight hours. Areas with more annual sunlight need fewer panels to produce the same energy. Check sunlight data for your location.
- Solar Panel Wattage – Panels vary in wattage outputs, normally from 250W to 400W for home systems. Higher efficiency panels produce more electricity with fewer panels needed. However, they usually cost more per watt.
Carefully considering these variables will determine the solar array size and number of panels suitable for an off-grid home. We’ll dive into the calculations next.
Calculating Electricity Usage
The first step in determining how many solar panels you need is calculating your total daily electricity usage. This involves taking an inventory of all the appliances and devices in your home and estimating how many hours per day each one is used.
For each appliance and device, you’ll need to find its wattage rating – this specifies how much power it consumes. The wattage should be printed somewhere on the device or in its user manual. If not, you can look up the average wattage for that type of appliance online.
Once you have the wattage and estimated daily use time for each appliance or device, you can calculate the kilowatt-hours (kWh) it uses in a day by multiplying its wattage by the number of hours it’s used, then dividing by 1000. For example:
- Refrigerator with 200 watt rating, running 24 hrs/day
- 200 watts x 24 hrs = 4800 watt-hrs
- 4800/1000 = 4.8 kWh/day
Do this calculation for every appliance and device, and add up the daily kWh totals. This gives you your estimated total daily electricity usage. Having this number will allow you to properly size your solar panel system.
Checking Sunlight Hours
The number of hours of peak sunlight per day is crucial for determining your solar panel needs. The peak sun hours is the amount of time where solar irradiance is at its maximum for the day. This refers to the maximum power output your solar panels can produce.
You’ll want to check government solar maps for your specific location to find the average peak sun hours per day for your area. In the United States, you can refer to the National Renewable Energy Laboratory’s PVWatts Calculator. Input your address and it will provide monthly and annual average peak sun hours.
For example, Phoenix, Arizona averages around 6 peak sun hours per day. Meanwhile, Seattle, Washington only averages about 4 peak daily sun hours. The more sunlight your location gets, the fewer solar panels you’ll need.
When sizing your solar system, focus on the peak sun hours instead of overall daylight hours. This number more accurately reflects how much energy your solar panels can realistically produce. Factoring in peak sun hours will prevent undersizing or oversizing your system.
Sizing the Solar System
When going off-grid, the size of your solar system will depend on your electricity usage. First, make a list of all electric devices and appliances you plan to run off-grid. Estimate the wattage for each one. Add up the total to determine your average daily electricity usage in watts.
Next, multiply this number by 1.3 to account for future electricity growth, as you may add more devices and appliances down the road. This gives you the total watts your solar system will need to generate per day.
For example, if your total estimated electricity usage is 3,000 watts per day, multiply this by 1.3 to get 3,900 watts. This means your solar system will need to produce at least 3,900 watts each day to meet your electricity needs both now and in the future.
With your required solar system wattage calculated, you can then determine how many solar panels you need, as well as the size of other components like batteries and inverters. Sizing your system correctly from the start will ensure it can fully power your off-grid home.
Calculating Panel Needs
The number of solar panels needed depends on the wattage of the individual panels. Most residential solar panels range from 250-400 watts each. It’s important to check the specs of the exact panels you plan to install to get the accurate wattage.
Once you know the total system wattage required and the wattage of your chosen solar panels, you can calculate the number of panels needed. Simply divide the total system wattage by the individual panel wattage.
For example, if your solar system needs to be 5000 watts total, and you select 300 watt panels, you would need 5000/300 = 16.7 panels. Rounding up, you would need 17 panels to meet the full 5000 watt system requirements.
When purchasing panels, make sure to get all panels that are the same make and model for optimal system performance. Having panels of different wattages on the same system can cause issues.
Roof Space Needed
The amount of south-facing roof space available is a key factor in determining how many solar panels your home can accommodate. When going off-grid, you’ll want to maximize the number of solar panels to ensure you can generate sufficient electricity.
To calculate the roof space required:
- Measure the total square footage of unshaded, south-facing roof on your home. South facing panels will provide the highest electricity production.
- Determine the dimensions of the solar panels you plan to install (standard sizes are around 65″ x 39″).
- Divide your total south roof square footage by the square footage of an individual panel. This will tell you the maximum number of panels your roof can fit.
For example, if you have 650 square feet of suitable south-facing roof space, and your planned solar panels are 25 square feet each:
650 sq ft roof space / 25 sq ft per panel = 26 panels
So in this scenario, you could install up to 26 solar panels on your south roof.
Be aware that roof obstructions like vents, chimneys, and skylights will reduce your usable space. It’s ideal to have at least 200 square feet of open roof space per 1,000 watts your system requires. Careful measurement and planning will help optimize the solar array for your particular home.
Batteries for Storage
When going off-grid, having batteries to store the energy captured by solar panels is essential. The most common types of batteries used for home solar systems are:
Lead-acid batteries – These are cost-effective but need more maintenance than other types. They come in two varieties – flooded lead-acid that need to be checked for water levels, and valve-regulated lead-acid (VRLA) that are sealed and maintenance-free.
Lithium-ion batteries – More expensive than lead-acid but last longer (up to 10 years or more). Very little maintenance required. Come in two main types – lithium nickel manganese cobalt oxide (NMC) and lithium iron phosphate (LFP).
Saltwater batteries – An emerging technology that uses saltwater electrolytes. Very long lifespan of up to 20 years and non-toxic. Higher upfront cost than lead-acid.
When sizing the battery bank, it’s important to calculate the total energy usage for essential appliances and devices. Multiply the wattage of each appliance by the average hours of use per day. Then multiply this by days of autonomy – the number of days the system should be able to provide power without sunlight. Common autonomy capacity is 3-5 days for a residential solar system.
Batteries will deplete faster if cycled more deeply each day. It’s ideal to stay within the 20-80% range for lead-acid, or 10-90% for lithium-ion batteries. Oversizing the battery bank allows for longer life by reducing the depth of discharge. Consulting an expert can help determine the right battery size and type for your solar system.
Average System Sizes
When deciding how many solar panels are needed for an off-grid home, it helps to know some general guidelines on typical system sizes. The average home solar system has between 20-40 panels, but this can vary significantly depending on factors like energy usage, roof space, and location.
For a roughly 2,000 square foot home, a typical system may have around 30 panels that are each 300 watts. This would equal a 9 kW system, which is generally enough to power general home appliances and electronics for an energy-efficient household. With this setup, the solar panels would take up about 450-600 square feet on the roof.
Bigger households with more occupants may need 40-50 panels to generate enough electricity. Smaller homes under 1,000 square feet can often get by with just 15-25 panels. The goal is to install enough panels to match at least 90-100% of your average energy usage.
When it comes to roof space, most panels are around 65 inches long by 39 inches wide. Using those dimensions, you can measure your usable roof space and determine roughly how many panels could fit. Just be sure to leave room for walkways, skylights, chimneys, and other roof features.
Having a general idea of average system sizes makes it easier to determine if your calculated needs are within a typical range. Keep in mind that every home is unique, but these averages provide a helpful starting point. Consulting with a solar installer is recommended to determine your specific requirements.
Recommendations
Going off-grid with solar power requires careful planning and calculation to determine how many solar panels your home or camping setup will need. Here’s a summary of the key factors to consider:
- Electricity Usage – Calculate how much power you use daily/monthly so you can size your solar system accordingly. Monitor usage over time.
- Sunlight Hours – Check sunlight data for your location to understand how much sun exposure you get. More sun = smaller system needed.
- Panel Wattage – Choose panels with higher wattages to produce more electricity. Combine panels for extra output.
- Roof Space – Measure available roof space for panel installation. Panels vary in size but around 1-2 panels per 100 sq ft is common.
- Batteries – Store excess solar energy in batteries for use when the sun isn’t shining. More storage capacity allows smaller solar systems.
For off-grid camping trips, start small with just enough panels and batteries for essentials like lights, phones, and a cooler. Aim for 100-200 watts of solar power as a minimum. Charge devices and batteries during the day so you have power at night. Add more panels for larger power needs.