Many people opt for off-grid living for various benefits, such as saving money, going green, or being more independent. Solar panels are a common and practical option to power your off-grid home with the sun’s plentiful and free energy. In this article, we will help you figure out how many solar panels you need to run a house off-grid, and what factors influence the number and size of the panels.
How Many Solar Panels to Run a House Off-grid?
One of the main difficulties of living off-grid is producing electricity, and solar power is the most feasible option. You need to install a solar system that is entirely independent and to do that, you must first determine how many solar panels you require. However, you have to take into account several factors that will influence the size and efficiency of your solar system.
These are the factors you need to consider
- Your annual energy consumption: The electricity you use at home in a year, in kWh. It varies with the appliances and devices you have and uses, such as lights, fans, fridges, TVs, computers, etc. A US house uses about 10,649 kWh/year or 29 kWh/day on average.
- Solar panel wattage: The electricity the solar panel can make per hour, in W. More wattage means more electricity. A solar panel has about 300W on average, so it can make 300W of electricity in an hour in ideal conditions.
- Solar panel efficiency: The percentage of sunlight that the solar panel turns into electricity. It changes with the panel’s angle, orientation, weather, and time. A solar panel has about 15-20% efficiency on average, so it makes 15-20W of electricity from 100W of sunlight.
- Solar panel types: There are three types of solar panels: monocrystalline, polycrystalline, and thin-film. Monocrystalline panels are the most expensive, but also the most powerful and efficient. Polycrystalline panels are cheaper but less powerful and efficient. Thin-film panels are the cheapest and most flexible, but also the least powerful and efficient. The type of solar panel affects how much space you need on your roof.
- Area of roof space available: The roof space should fit the number of solar panels you need for your energy needs. It should face south or west in the Northern Hemisphere, or north or east in the Southern Hemisphere, for the best sunlight. The roof space should be strong enough to hold the solar panels and have a four-inch gap between them and the roof to avoid overheating and allow airflow.
- Location and climate of your area: The hours per day when the sunlight is at least 1000 W/m2, which is the minimum for good solar power. It depends on the place, season, weather, and time. More peak sun hours means more electricity from your solar panels. The US has 3 to 5 peak sun hours per day on average, depending on the area and the season.
- Battery storage capacity: The electricity the battery can store and give when the solar panel is not making enough electricity, like at night or on cloudy days. It depends on the battery type, size, DOD, and SOC. The DOD and SOC are the best between 50% and 80% and between 20% and 50%, respectively, depending on the battery chemistry and design.
- Battery inefficiency: The energy loss during the battery charging and discharging, in percentage. It depends on the battery quality and performance. The battery inefficiency is about 10-20% on average.
- Inverter inefficiency: The energy loss during the DC to AC electricity conversion, in percentage. It depends on the inverter’s quality and performance. The inverter inefficiency is about 10-20% on average.
How to calculate the number of solar panels you need to go off-grid?
Once you have considered the factors, you can estimate the number of solar panels you require. Here is a guide for you that explains each step in detail.
Step 1: Assess your electricity usage.
To calculate your energy use, look at your most recent power bill and find the kWh amount. This is usually shown near the end of the bill, along with the price/kWh.
Step 2: Calculate how many peak sunlight hours your area receives daily.
To go off-grid, you need to know your area’s peak sunlight hours. These are not the same as the hours from sunrise to sunset. They are the hours when the sun is strongest and the panels are most efficient.
For example, let’s look at some of the best solar states in the US: California, Texas, Florida, North Carolina, and Arizona.
The National Renewable Energy Laboratory gives the solar irradiance data for September.
| State | Average Daily Peak Sunlight Hours (September) |
| California | 5.75 |
| Texas | 5.5 |
| Florida | 4.75 |
| North Carolina | 4.5 |
| Arizona | 5.6 |
Step 3: Calculate the size of the solar system you will need.
The size of your solar system will depend on your area’s peak sunlight hours. To find the average peak sunlight hours per month, multiply your daily hours by 30.
Let’s use the best solar states as examples: California, Texas, Florida, North Carolina, and Arizona. Then, divide your monthly electricity usage (let’s say 1800kWh) by the monthly sunlight hours.
You can use this formula
Required Solar System Size = Monthly Electricity UsageAverage Monthly Peak Sunlight Hours
Here is a table that shows the solar system size for each state based on the average peak sunlight hours per month.
| State | Average Monthly Peak Sunlight Hours (September) | Required Solar System Size |
| California | 5.75*30 = 172.5 | 10.43 kW |
| Texas | 5.5*30 = 165 | 10.90 kW |
| Florida | 4.75*30 = 142.5 | 12.63 kW |
| North Carolina | 4.5*30 = 135 | 13.34 kW |
| Arizona | 5.6*30 = 168 | 10.71 kW |
Step 4: Determine the number of solar panels you will need.
To convert the kW solar system to watts, you need to multiply the system size by 1000.
Let’s use the same states as before: California, Texas, Florida, North Carolina, and Arizona.
You also need to choose the wattage of your solar panel. A common choice for residential installations is a 350-400 W solar panel. Let’s use a 350W solar panel as an example.
To find the number of solar panels required, divide the solar system wattage by the solar panel wattage.
Here’s a table that shows how many 350W solar panels you need for your monthly energy usage of 1800 kWh.
| State | Solar System Size (Watts) | Number of 350W Solar Panel Required (Round Off) |
| California | 10430 | 30 |
| Texas | 10900 | 32 |
| Florida | 12630 | 36 |
| North Carolina | 13340 | 38 |
| Arizona | 10710 | 31 |
How Much Solar Power for Off-Grid Cabin?
If you are planning to use solar power for an off-grid cabin, you may have different energy needs than a regular home. Depending on the size, design, and location of your cabin, as well as the appliances and devices you use, your solar power requirements may vary.
To give you a general idea, here is a table that shows the approximate solar power needs for different types of off-grid cabins
| Cabin Type | Size | Appliances | Solar Power Needed |
| Basic | 400 sq ft | Lights, fan, radio, phone charger | 500 W |
| Moderate | 800 sq ft | Lights, fan, radio, phone charger, TV, fridge, microwave, water pump | 1500 W |
| Luxury | 1200 sq ft | Lights, fan, radio, phone charger, TV, fridge, microwave, water pump, washer, dryer, dishwasher, oven, AC | 5000 W |
As you can see, the more appliances and devices you have, the more solar power you will need. You can follow the same steps as discussed above to determine the amount of solar power required for your cabin after calculating and optimizing your power usage and needs.
Tips to Reduce Consumption While Living Off-Grid
To live off-grid with solar panels, you need to be mindful of your energy use and cut it down as much as you can. This will save you money, protect the environment, and make you more self-reliant.
Here are some tips to lower your energy use off-grid
- Choose energy-efficient appliances and lights, such as LED bulbs, solar-powered devices, and low-wattage appliances. Use timers, sensors, and dimmers to manage the lighting and prevent energy waste.
- Insulate your home well, use curtains and blinds to adjust the temperature, and dress suitably for the season. Use fans, fireplaces, and wood stoves to heat and cool your home naturally.
- Cook fast and with less energy using a pressure cooker, a slow cooker, or a solar oven. Plan your meals, cook in large quantities, and use leftovers inventively to avoid food and energy waste.
- Save water by collecting rainwater, installing a water filter, and using a low-flow showerhead and faucet. Reuse greywater for watering plants, flushing toilets, and washing clothes.
- Be minimalist and avoid buying unnecessary items, declutter your home often, and donate or recycle what you don’t need. This will save you money, space, and resources, and make your off-grid living more pleasant and easy.
Conclusion:
To sum up, many people find it worthwhile and satisfying to power their homes with solar panels off the grid. However, this requires knowing how many solar panels are needed depending on your energy use, location, and choices. Although an off-grid solar system may have a high upfront cost, it will pay off in the long run by reducing your electricity bills.