Renewable energy sources like solar and wind are ideal for powering equipment in remote locations. In this article, we’ll outline a step-by-step process for sizing an off-grid solar system so you can generate electricity even when you’re miles from the nearest power line.
These types of systems power off-grid homes, as well as a variety of industrial applications where equipment needs to be powered at remote work sites. Common applications include lighting, telecommunication equipment, sensors, environmental monitors, security cameras, traffic signals, water pumps, cathodic protection systems, and anything else that requires reliable power in a remote location.
The following guidelines are intended to help size an off-grid solar system based on a given location, energy requirements, and desired days of autonomy (how long the battery bank can supply power before it needs to be recharged).
FREE Solar Battery Guide
Step 1: Determine Energy Requirements
First, you need to know how much energy the equipment uses on a daily basis. This is measured in watt-hours or kilowatt-hours per day. For example, let’s assume the equipment consumes 10 watts of power and operates 24 hours a day:
10 Watts x 24 hours = 240 watt hours per day or .24 kWh per day
How do you find this information? Check the data sheet or manual for your equipment to find out how much power it consumes (in Watts), and then multiply that by the number of operating hours per day. If possible, use a meter to measure the power consumption for an accurate real-world measurement.
If you are using an inverter to produce AC power for a load, remember to account for the inverter’s self-consumption and efficiency losses. Inverters consume a small amount of power while they are operating. Reference the inverter spec sheet, and add the self-consumption to your daily total. Inverter self-consumption typically ranges from under 1 watt, to around 30 watts depending on the inverter.
Efficiency losses can be from 5% to 15% depending on the inverter and how much it’s loaded. This will be accounted for when sizing the batteries. It’s important to invest in a quality, high-efficiency inverter.
Step 2: Evaluate Site Location
Next, determine where the system will be installed to estimate available solar energy.
Use a solar insolation map (also called a ‘sun hours map’) to estimate available PV resources. The system should be sized based on the month with the highest power consumption and/or lowest solar resource, typically December or January.
The National Renewable Energy Laboratory (NREL) has an online resource for mapping available solar radiation. Here is a map of the minimum daily sun hours in January in the United States with a south-facing array:
Most of the US has fairly low solar insolation in January. Generally, 2.5 sun hours is a good estimate, but it could be lower or higher depending on your location. We will use 2.5 minimum sun hours for our example.
Solar panels are designed to be installed in full sun. Shade is going to impact performance. Even partial shade on one panel will have a large impact. Inspect the site to make sure your solar array will be exposed to full sun during daily peak sun hours. Keep in mind that the sun’s angle will change throughout the year.
There are a few other things to think about at this point:
System voltage:Determine what power requirements your equipment has. Off-grid PV systems typically output these common voltages: 12Vdc, 24Vdc, 48Vdc, or 120Vac.
Solar panels and batteries use DC power, and some equipment can be wired directly to the batteries provided it can handle real-world battery voltages. These can range from 10-15 volts for a 12-volt system, 20-30 volts for a 24-volt system, and 40-60 volts for a 48-volt system.
Days of autonomy:The number of days the equipment must operate on battery power with limited solar power. Between 5-20 days is typical, depending on the area and expectations for operating performance. You need enough autonomy to keep the equipment operating through extended periods of overcast weather.
Step 3: Calculate Battery Bank Size
Now we should have enough information to size the battery bank. After the battery bank is sized, we can determine how much solar power is required to keep it charged.
Here is how to calculate battery bank size in our example of 240Wh/day based on lead-acid batteries:
First, we need to account for the inefficiency of the inverter (if you are using an inverter). Depending on the equipment, 5-15% is usually reasonable. Check the spec sheet for the inverter to determine the efficiency. We’ll use a 10% inefficiency for this example:
240 Wh x 1.1 efficiency compensation = 264 watt hours
This is the amount of energy drawn from the battery to run the load through the inverter.
Next, we need to account for the effects of temperature on a battery’s capacity to deliver energy. Lead-acid batteries lose capacity as temps go down and we can use the following chart to increase battery capacity, based on the expected battery temperature:
For our example, we’ll add a 1.59 multiplier to our battery bank sizeto compensate for a battery temperature of 20°F in the winter:
240 Wh x 1.1 x 1.59 = 419.76 watt hours
Next, account for the efficiency loss that occurs when charging and discharging batteries. Typically we use 20% inefficiency for lead-acid batteries, and 5% for Lithium-ion.
240 Wh x 1.1 x 1.59 x 1.2 = 503.71 watt-hours minimum energy storage requirement
This is for a single day of autonomy, so we need to then multiply it by the number of days of required autonomy. For 5 days of autonomy, it would be:
504 wh x 5 days = 2,520 watt hours of energy storage
As you can see, the battery bank size is quickly increasing due to factors including temperature and required days of autonomy. All of these things affect your battery bank size significantly and need to be carefully considered.
Lead-acid batteries are commonly rated in amp hours (Ah) rather than watt-hours (Wh). To convert watt-hours to amp hours, divide by the system’s battery voltage. In our example:
2,625 Wh÷ 12v = 220 Ah 12V battery bank
2,625 Wh ÷ 24v = 110 Ah 24V battery bank
2,625 Wh ÷ 48v = 55 Ah 48V battery bank
When sizing a battery bank, always consider the discharge depth, or how much capacity is discharged from the battery. Sizing a lead acid battery for a maximum 50% depth of discharge will extend the battery’s life. Lithium batteries are not as affected by deep discharges, and can typically handle deeper discharges without substantially affecting battery life.
Total required minimum battery capacity: 2.52 kilowatt hours
Note that this is the minimum amount of battery capacity needed, and increasing the battery size can make the system more reliable, especially in areas prone to extended overcast weather.
Step 4: Figure Out How Many Solar Panels You Need
Now that we’ve determined battery capacity, we can size the charging system. Normally we use solar panels, but a combination of wind and solar might make sense for areas with good wind resource, or for systems requiring more autonomy. The charging system needs to produce enough to fully replace the energy drawn out of the battery while accounting for all efficiency losses.
In our example, based on 2.5 peak sun hours and 240 Wh per day energy requirement:
240 Wh / 2.5 hours = 96 Watts PV array size
However, we need to account for real-world losses caused by inefficiencies, module soiling, aging, and voltage drop, which are generally estimated to be around 15%:
96 array watts / .85 = 112.94 W minimum size for the PV array
Note that this is the minimum size for the PV array. A larger array will make the system more reliable, especially if no other backup source of energy, such as a generator, is available.
These calculations also assume that the solar array will receive unobstructed direct sunlight from 8 AM to 4 PM during all seasons. If all or part of the solar array is shaded during the day, an adjustment to the PV array size needs to be made.
One other consideration needs to be addressed: lead-acid batteries need to be fully charged on a regular basis. They require a minimum of around 10 amps of charge current per 100 amp hours of battery capacity for optimal battery life. If lead-acid batteries aren’t recharged regularly, they will likely fail, usually within the first year of operation.
The maximum charge current for lead acid batteries is typically around 20 amps per 100 Ah (C/5 charge rate, or battery capacity in amp hours divided by 5) and somewhere between this range is ideal (10-20 amps of charge current per 100ah).
Refer to the battery specs and user manual to confirm the minimum and maximum charging guidelines. Failure to meet these guidelines will typically void your battery warranty and risk premature battery failure.
Here are standard configurations of PV arrays with battery banks. The battery capacity calculated in the previous step can be compared against this table to find a suitably sized system:
|Array Size: PV Watts (STC)||Battery Bank Size:|
Watt Hours (@ C20 rate)
|Battery Bank Ah Capacity|
|100-175||600||50Ah @ 12Vdc|
|200-350||1,200||100Ah @ 12Vdc|
50Ah @ 24Vdc
100Ah @ 24Vdc
|800-1,400||4,800||400Ah @ 12Vdc|
200Ah @ 24Vdc
100Ah @ 48Vdc
|2,000-3,000||9,600||800Ah @ 12Vdc|
400Ah @ 24Vdc
200Ah @ 48Vdc
|4,000-6,000||19,200||800Ah @ 24Vdc|
400Ah @ 48Vdc
|8,000-12,000||38,400||800Ah @ 48Vdc|
This information is intended to be a general guide and there are a lot of factors that can influence system size. There are also alternative options such as incorporating a backup gas generator or wind generator(s) to reduce the minimum battery requirement.
If the equipment is critical and in a remote location, it pays to oversize it because the cost of maintenance can quickly exceed the price of a few extra solar panels. On the other hand, for certain applications, you may be able to start small and expand later depending on how it performs. System size will ultimately be determined by your energy consumption, the site location and also the expectations for performance based on days of autonomy.
If you need help with this process, feel free to schedule a free consultation with us and we can design a system for your needs based on the location and energy requirements.
To figure out how to size your solar system, take your daily kWh energy requirement and divide it by your peak sun hours to get the kW output. Then divide the kW output by your panel's efficiency to get the estimated number of solar panels you'll need for your system.How big of a solar system do I need off-grid? ›
If your energy needs are around 1,000 to 5,000 watts, go for a 24 volt system. If your energy needs are over 3,000 watts, go for a 48 volt system. Large off-grid houses often use 48 volt systems.How do I calculate what size solar system I need? ›
You can calculate how many solar panels you need by multiplying your household's hourly energy requirement by the peak sunlight hours for your area and dividing that by a panel's wattage. Use a low-wattage (150 W) and high-wattage (370 W) example to establish a range (ex: 17-42 panels to generate 11,000 kWh/year).How do you calculate and design off-grid solar system? ›
- Calculation 1. (Load WH/day) / Base Battery Voltage = (Load AH/day)
- Calculation 2. ...
- Base Battery Voltage. ...
- Days of Autonomy. ...
- Max DOD. ...
- Cold Temp Factor. ...
- Putting it all together:
- Calculation 1.
The Tesla Powerwall for Off Grid systems is able to be stacked up to 9 times, meaning you can have up to 126kWh of energy storage, but most off grid properties will not need more than one or two of the Tesla Powerwalls to ensure the property will always have power available, along with an appropriately sized solar ...How do you calculate off-grid system size? ›
- Battery bank size (kWh) = Daily energy use (kWh) x Number of days of autonomy / (1 – SOC)
- Battery bank size = 1.9 x 3 / (1 – 0.5) = 11.4 kWh. ...
- Amp-hours = 1000 x Energy storage (kWh) / Battery Voltage (Volt)
- Amp-hours = 1000 x 11.4 / 24 = 475 Ah at 24 Volt.
If you want to save the most money possible, you'll need enough battery storage to cover your energy usage when your solar panels aren't producing – somewhere around 2-3 batteries. If you want to keep the power on when the grid is down, you'll usually just need one solar battery.How much electricity does a 4kW solar system produce per day? ›
For example, an average 4kW solar system can produce up to 16kWh of power per day. In UK homes, solar panel kilowatts may vary between 1kW to 4kW. You may get more solar panels or those with bigger kilowatt capacity, like a 6kW solar panel.How much power does a 5kW solar system produce per day? ›
Yes, that's it! So a 5kW solar system should on average produce around 20kWh per day. You will likely see much more power produced during great solar days in summer, probably up to 30kWh and much less power produced during a cloudy winter day maybe lower than 10kWh.How many solar panels do I need to charge a 100ah battery? ›
Charging your battery at 12 volts and 20 amps will take five hours to charge a 100 amp hour battery. By multiplying 20 amps by 12 volts, 240 watts is how big of a panel you would need, so we'd recommend using a 300w solar panel or 3 100 watt solar panels.
If you don't have an alternator or DC loads, 48V systems can be a great way to have high AC output and a large solar array. This makes 48V very popular with off-grid cabins.How do you size an off-grid inverter? ›
4 to 8 kW: Most off-grid homes. 8 to 16 kW: Larger off-grid homes, farms or ranches and small businesses. While inverters are available in larger and smaller sizes than those listed above, these are the most popular options, with 4 kW and 8 kW being the top choices.What is the grid calculation? ›
Calculation grids are used to quantify Illuminance values within a rectangular boundary using regularly spaced light meter positions. Two versions of the Calculation Grid are available - 2 Point and 3 Point specification. The only difference between the two is the alignment of the grid in AGi32's environment.How many Tesla batteries do I need to go off-grid? ›
Using Tesla Powerwall batteries with 95% depth-of-discharge, that means you'll need a storage system with a total capacity of about 184 kWh, which comes out to 14 individual Tesla Powerwall batteries.What is the 120% rule for Tesla Powerwall? ›
The NEC 120% rule limits the size of additional power sources (PV or battery) to within an acceptable safety limit based on the equipment label rating. In this case, the PV breaker would be limited to a maximum of 40 amps.How long will 4 Powerwalls last? ›
The Tesla Powerwall is a home battery that stores solar energy and can last up to 10 years with proper maintenance. The Powerwall can provide backup power during an outage, and it can help you save money on your electric bill.What is a typical off grid system? ›
Off-grid system designs
An off grid solar system includes solar panels, an inverter and a battery storage solution. The power that's generated by the system is used to power the home and appliances, with any leftover power stored in batteries to use during an evening or on a rainy day.
The widths of the columns are always up to the designer, but in terms of standard practices, the traditional number of columns to use is 12 on desktop, 8 on tablet, and 4 on mobile. Most grids have 60-80px column widths.How many batteries do I need for a 10kW off-grid solar system? ›
In conclusion, a 10kW solar system typically requires a battery bank with a capacity of 20-30kWh, which can require between 100-150 batteries with a capacity of 200Ah each.What happens when off-grid solar batteries are full? ›
What Happens When Solar Power Batteries Are Full? Solar power systems use batteries to store solar energy. However, if the power generated exceeds the solar battery's capacity, it can overcharge the system. An overcharged solar system can severely damage a battery's life.
No, there is no limit to the number of solar panels you can have. However, there may be a limit on how much power your system is allowed to generate. Some utility companies limit the amount of electricity that a grid-tied solar system can generate.Can solar power run an air conditioner? ›
You Can Run an Air Conditioner on Stored Solar Power, if:
Proper design and sizing is essential to any solar PV system, but in the case of using solar energy to power your air conditioner, you will need to have enough energy available to cover the hottest days of the year.
According to the United States Energy Information Administration, the average American household consumed 10,632-kilowatt hours (kWh) of electricity last year. The average kWh per month was 886, while the average kWh per day was 29.What is good solar production per day? ›
Solar power from a single panel in a solar panel system typically produces about 2 kWh per day. However, the amount a single panel will produce depends on a wide variety of factors.How many batteries do I need for a 5kW solar system? ›
A hybrid inverter 5kw would require a minimum 450 to 500 ah 12 V battery. Alternatively, you can have two separate batteries of 250ah 12V that would power the system for 30 to 45 minutes. If you demand to run the inverter for 1 hour, you would require 750ah 12 V batteries.Is 5kW enough to run a house? ›
A 5 kW solar power system is ideal for most medium-large families (up to five people) in average sized homes – generally up to four bedrooms. These systems are popular because they cover slightly more than the average electricity bill in these scenarios.How many AC can 5kW run? ›
A 5kW solar power system is sufficient in supporting the electricity needs of a 2BHK, 3BHK and any other medium-sized houses with 2-3 ACs. It is a medium-capacity solar system for homes that has the capacity to generate up to 20kWh (units) of electricity.How long will a 100Ah battery run a fridge? ›
If you're using a 12V 100Ah lead acid battery, you can expect the fridge to run for about 30-50 hours because lead acid batteries can only be discharged to 50%.How long will a 100Ah lithium battery run an appliance that requires 400W? ›
|Appliance Power Draw (Watts):||How Long Will 100Ah Battery Last:|
The charge time depends on the battery capacity, and it takes around 2.5 hours for a 200-watt solar panel to charge 100Ah of battery capacity.
Installing your lithium-ion battery pack inside is the best way to protect them from cold weather. Furthermore, your batteries should be ultimately located in a place with an ideal temperature (60-80 degrees Fahrenheit) with extra insulation.Is 12v or 24v better for off-grid? ›
If your energy needs are around 1,000 to 5,000 watts, go for a 24 volt system. If you're looking to build a smaller, DIY system for your RV, van, or tiny home, go for a 12 volt system.Which battery is most suitable for off-grid system application? ›
Lead-acid batteries have been used most often in off-grid applications, and since people have a lot of experience with them some people will continue to use them without considering other options.What happens if my inverter is too big? ›
Using an inverter that is too large is also inadvisable. Inverters work at optimal efficiency when operating at (or close to) their maximum capacity. Therefore, using an inverter that is considerably larger than your solar array can make the inverter less efficient.Should you oversize your inverter? ›
Is it safe to oversize solar inverters? Just about every inverter in the market is designed to safely manage one-third (133%) of additional energy from the solar array. As long as the solar system is designed and installed by a reliable company, there should be no safety concerns with oversizing your inverter.How do you calculate battery sizing for solar system? ›
To find out the size of battery, calculate as follows: 4.1 Calculate total Watt-hours per day used by appliances. 4.2 Divide the total Watt-hours per day used by 0.85 for battery loss. 4.3 Divide the answer obtained in item 4.2 by 0.6 for depth of discharge.
In a nutshell, the grid method involves drawing a grid over your reference photo, and then drawing a grid of equal ratio on your work surface (paper, canvas, wood panel, etc). Then you draw the image on your canvas, focusing on one square at a time, until the entire image has been transferred.What is the grid scale method? ›
The grid method is a technique used in art that involves dividing an image into a series of smaller, more manageable sections using a grid. A grid is typically drawn over the reference image, and then students use the grid to draw the image on their own piece of paper, carefully replicating each section of the grid.What is the grid square method? ›
"The Grid Square System" [*1] uses longitude and latitude to section an area into a grid. The first area section (1st grid) is based on a difference of one degree of longitude and 40 minutes of latitude. The second area section (2nd grid) divides the first into 8 parts of equal length and breadth.How long can Tesla Powerwall run AC? ›
It can run an air conditioner or heater while also providing power for other appliances. The built-in rechargeable battery offers up to 10 hours of backup power before requiring its next charge.
While off-grid, each Powerwall can provide up to 5 kW of continuous power. You can use Go Off-Grid to identify the kinds of heavy loads your Powerwall system can support.What is the life expectancy of a Tesla solar battery? ›
What is the lifespan of a Tesla Powerwall solar battery? On paper the average lifespan of a Tesla Powerwall is around 20 years. However, this number can vary depending on how often you use your battery and how much of it you use.How many solar panels do I need for Tesla Powerwall? ›
In general, it will take between 4 and 8 solar panels to charge a Tesla Powerwall. This means that the number of solar panels you need will vary based on the wattage of the solar panel, the size of the Powerwall, and the climate.What happens if you overload Tesla Powerwall? ›
Starting some loads with high inrush current during a power outage, like air conditioners and motors, may overload Powerwall and cause it to stop providing power to your home. If this occurs, turn off these loads, and Powerwall will attempt to restart within a minute.How many Tesla Powerwalls does it take to run a house? ›
You will need three or more backup batteries for the whole house in most cases. They will be enough for essential loads and such large appliances as a central A/C, electric range, off-grid vehicle charging, electric dryer, electric water heater, pool equipment, etc.How many Powerwalls do you need to go off the grid? ›
The Tesla Powerwall for Off Grid systems is able to be stacked up to 9 times, meaning you can have up to 126kWh of energy storage, but most off grid properties will not need more than one or two of the Tesla Powerwalls to ensure the property will always have power available, along with an appropriately sized solar ...How efficient is Tesla Powerwall after 10 years? ›
Tesla Powerwall 2 systems come with a 10-year manufacturer's warranty for unlimited cycles and 80% of the original energy capacity, when the system is charged using solar energy. This means that if your Powerwall falls below 80% of the original capacity during those 10-years, you qualify for a replacement.How many Powerwalls do I really need? ›
In very general terms, one Powerwall should be able to cover your emergency circuits, lights, and outlets. If you are looking to power larger appliances 2-3 Powerwalls is a good start.How big of a solar system do I need for a 2000 square foot house? ›
So, a 2,000 square foot home would be allowed a solar array of 4,000 watts. Depending on the type of panel that you choose, a system of this size would be anywhere from 12-18 solar panels. Keep in mind, this formula to estimate consumption varies depending on who provides your electricity.How big of a solar system does it take to power a house? ›
How many solar panels does it take to power a house? Based on average electricity consumption and peak sun hours, it takes around 17 400-Watt solar panels to power a home. However, this number will vary between 13-19 based on how much sun the panels get and how much electricity the home uses.
How many solar panels power a house? Key takeaways. An average home needs between 17 and 21 solar panels to fully offset utility bills with solar. The number of solar panels you need depends on a few key factors, including your geographic location and individual panel specifications.What can a 5kW off-grid solar system power? ›
You can run a washing machine, air conditioner, fridge, water heater, oven, and TV with a 5kw solar system. If you have these appliances in your home, a 5kW solar system is sufficient.How many kW to power a 2000 sq ft house? ›
|Square Footage||Electrical Usage (kWh)||Average kWh / Square Foot|
A typical system size for a home that size is about 7 kilowatts (kW). This means that you would need about 7 kW of solar power installed on your property in order for it to be eligible for tax credits and save money on your electric bill.How many solar panels do I need for a 2200 sq ft house? ›
On average, it takes between 28 to 32 solar panels to power a house. This will cover 100% of the energy costs for a 2,500 sq ft home. The exact number of panels you'll need will vary based on the home's size, placement of the panels, geographic locations, and panel efficiency.Can my house be 100 solar? ›
Fact vs Myth: Can Solar Energy Really Power an Entire House? [2023 Update] One of the most frequently asked questions by homeowners in regard to solar power is, “can it really power my entire house?” The answer to that is actually quite simple – yes, solar can indeed power your entire home.How many kW required for home? ›
Now, let's consider the energy needs of a typical household in India. According to the Central Electricity Authority (CEA), the average per capita consumption of electricity in India is around 1,200 kWh per year. This means that the average household in India uses around 3,600 kWh of electricity per year.How many kW does it take to run a house? ›
How Many Kilowatts Does It Take to Power a House? With the average American home consuming 900 kWh a month or 30 kWh a day, that brings the total yearly usage to around 10,800 kWh. This means that most solar energy systems will need to be large enough to produce this many kWh's in a given year.How many solar panels do I need for a 3 000 sq ft home? ›
A 3000-square-foot home, on average, will use 1,185 kilowatt hours of energy per month. If the home falls in line with this average, it will need between 27 and 30 panels to provide an adequate amount of power.Is 10kW solar enough? ›
Realistically, a well-maintained 10kW solar panel array in the prime of its life can be expected to generate between 10,800 and 14,400 kWh of electricity annually in most locations, given the amount of sunshine they receive . The good news is that this is clearly enough to meet the needs of the average homeowner.
A 400 amp-hour 6 volt battery can provide around 2.4 kilowatt hours of power. A three-day battery bank planned to provide 90 kilowatt-hours of electricity to an average American household. The previous example battery can provide2,4 kilowatt hours, while 38 batteries would be needed.How many batteries do I need for a 10kW solar system? ›
In conclusion, a 10kW solar system typically requires a battery bank with a capacity of 20-30kWh, which can require between 100-150 batteries with a capacity of 200Ah each.