Today, most of our energy comes from non-renewable sources like coal, crude oil and natural gas. Those sources cost money and they pollute the environment. And, that cost is passed on to you. Fortunately, solar energy solves this problem. Therefore, let’s see how to design a solar system that meets your needs.
In this article, we’ll look at your solar options and break down each component that goes into the design. For each component, we’ll see how to calculate and determine the size and features needed. Then, we’ll look at solar installation. Now, read on to see exactly how to design a solar system correctly.
The basis for solar system design
In short, your solar system design is based on the number of kWh or kilowatt-hours your household requires per day. As such, that will determine how much energy your system must produce for you. You’ll need to calculate this carefully since your household energy demand will vary throughout the year.
There are two calculations that will help determine your household energy usage. First, calculate your energy consumption for each month of the year. If you are connected to the grid, just retrieve this info from your monthly electric bills or your annual summary. If not, we’ll walk through the steps one-by-one.
This info is important since solar panels produce different amounts of power at different times of the year. For example, your solar panels must produce enough kWh per day in December, the lowest solar production month of the year. Soon, we’ll determine your solar panel requirements as we walk through how to design a solar system.
Calculate household energy demand
Although your household energy demand varies throughout the year, start by calculating the basics in kWh. To begin, water usage, appliance usage, and general electricity usage is where to start. Keep in mind, only calculate water-usage if you use an electric water pump to provide water to your household.
If your household uses a water pump, check your water pump’s wattage – it will vary from 250W to 1,100W. Then, take the wattage of your water pump and multiply it by the number of daily hours it runs. Finally, divide that by 1000 for the number of kWh your pump uses.
Calculate each appliance individually. As such, use the wattage value for each of your own electrical appliances and products. This will provide the most accurate estimate. Then, add them all together to calculate your total annual energy consumption.
Estimate the number of daily hours each electric appliance and product runs at the most. For example, estimate the number of hours you use each electronic device. Examples include TVs, computers, gaming systems, home audio, and so on. Then, calculate each based on the wattage stated on each label.
Performing the household energy calculation
To determine your daily energy consumption, use the following formula:
(Watts × Daily hours used) ÷ 1000 = Daily kWh of consumption.
To calculate your annual energy consumption, use the following formula:
Daily kWh of consumption × Number of days used per year = Annual energy consumption.
This is a statement about annual electricity consumption in the U.S. by the U.S. Energy Information Administration:
“In 2020, the average annual electricity consumption for a U.S. residential utility customer was 10,715 kilowatthours (kWh), an average of about 893 kWh per month. Louisiana had the highest annual electricity consumption at 14,407 kWh per residential customer, and Hawaii had the lowest at 6,446 kWh per residential customer.”
Estimating home appliance power usage
In the following article from Energy.Gov about estimating appliance and home electronic power usage, estimate the total electricity used by your appliances with the following four methods:
- Review each Energy Guide label to estimate the individual unit’s average energy consumption.
- Use an Electric Consumption Meter to uncover how much electricity each appliance consumes.
- Install a whole-house energy monitoring system to monitor your actual energy usage.
- Calculate your total annual energy consumption using the formulas shown below.
Components of a solar system
While you may find many variations and custom options that go into a solar system, there’s an assortment of essentials to identify and explain in simple terms. As such, let’s take a walk through each part to understand the basic system and what essential solar components go into it prior to installation.
A sufficient solar system is a self-sustaining household solar system that also connects to the power grid. That means, it provides power from three sources: solar energy, battery bank backup, and your electrical utility grid.
Off-grid systems are enormously more complicated than common grid-connected solar systems. But, over 300,000 homes use them for their energy needs around the world. They know that when connected to the grid, they’re dependent on an external supplier for all their power. And when that power grid goes down, so does their power supply.
Check out the following components that make up a solar system. In this section, equip yourself with important knowledge while learning how to design a solar system. That way, you won’t run into surprises when purchasing you own off-grid solar system or hybrid solar system.
Solar panel arrays for free electricity
Solar panel arrays are frameworks of panels filled with photo-voltaic cells. They generate DC electricity from the energy projected by sunlight called photons. This process was first discovered by Alexandre-Edmond Becquerel back in 1839.
Solar panel arrays require direct sunlight to produce maximum power output. Even on cloudy days, solar panels absorb solar energy and produce power. But of course, power output reduces significantly by 25% to 40% compared to sunny days.
Panel efficiency deals with the electrical output of each panel: 320W, 290W, 270W etc. This translates into the number of panels you’ll need. To calculate, power rating divides by total panel area. That means, having a larger panel doesn’t always equate to higher efficiency.
Maximize your available sunlight
To maximize the amount of sunlight your solar panel array receives, face them to the sun. Avoid installing them in shade under trees or nearby buildings. Although solar system installers help you determine the best placement for your panels, plot a sun chart. Use a solar tracker to determine how much sun your solar panels are likely to receive on a typical day.
Calculating the total sunlight your solar panel array receives is important. But a more accurate calculation is the amount of power your panels produce during peak sun-hours. First, peak sun hours are not the same as hours of daylight. Peak sun hours are the maximum solar energy available during a typical day. To be specific, a peak sun hour is an hour where intensity of sunlight is 1000W per square meter.
Factors that determine peak sun hours are time of day are as follows. To begin, noon is the highest level. Then, proximity to the equator gets calculated. Finally, each season is calculated – summer has the highest level. As an example, your solar panel array may receive an average of seven hours of sunlight per day, the average peak sun hours may actually be only three or four hours.
For a resource, NASA’s Power Project provides solar and meteorological data sets from NASA research. This is for support of renewable energy, building energy efficiency and agricultural needs.
How to design a solar system with power optimizers
Power optimizers maximize the energy harvest from solar power systems. They achieve this by individually tuning the performance of each panel within the solar panel array. As you’ll see, power optimizers are especially useful when the component performance in a distributed system varies due to shading or facing different directions.
Shown here is a voltage converter that connects to each solar module in your solar panel array. In short, it turns them into smart modules. By constantly tracking the MPPT or Maximum Power Point Tracking of each individual solar module, power optimizers increase system energy production.
When you attach these power optimizers to each solar module, installers can easily monitor system performance reliably. In other words, installers will be able to track, pinpoint, and resolve issues at any point along a string with surgical precision. This lowers maintenance costs dramatically over the life of your system.
120V AC solar system inverter-charger
Knowing that your solar panel array and battery bank generate DC or Direct Current, the electricity must be converted into 120V AC or Alternating Current for your home. To explain, the electricity in your home must be 120V AC. In other words, your solar power inverter-charger creates power that mimics that normally coming from a utility grid.
In addition to providing 120V AC to the home, your inverter-charger is the heart and brains of your off-grid solar system. First, it regulates battery bank charging and manages battery charge levels to maintain battery life. Then, it monitors and displays power consumption and battery status to provide system status.
How to design a solar system with batteries
Your battery bank provides complete electrical independence – it makes off-grid solar systems possible. To explain, it provides power at night when your solar panel array isn’t producing. Also, it provides extra power in those moments when power consumption spikes above what your solar panel array provides.
As you know, not having a grid connection means you need a reliable way to store the energy generated during the day for later use. Therefore, it’s critical to have a battery bank to store enough energy to get you through each night. Also, they must support off-peak production periods like cloudy days.
Traditionally, lead-acid deep cycle battery systems were the most common and reliable option for off-grid solar systems. Though a proven technology lasting over a decade, they must be kept at room temperature and not be discharged often. To explain, high temperatures, low temperatures, and fully draining lead-acid batteries internally damages and degrades them.
Many advantages of Lithium-ion battery banks
Your best battery option for your off-grid solar system is the lithium-ion battery bank, an advanced storage device optimized for long lifespan, fast recharge, and high efficiency. Most notably, they’ve become extremely popular for their high efficiency ranging from 92% to 98%.
Lithium-ion battery banks are compact, lightweight and scalable. On top of that, they provide flexible sizing for additional capacity down the road. In other words, lithium-ion batteries may be added in the future as you’re power needs increase or if you just increase power storage for more peace of mind.
One giant advantage of lithium-ion battery banks are their ability to sustain a low or partial charge levels for prolonged periods without negative effects. Compare this to sulfation that is a common problem with lead-acid batteries. Also, lithium-ion batteries provide high charge rates – charge times are up to 70% faster than lead-acid.
Calculating the solar system size
Now that you have a strong understanding of your annual household power consumption and your area’s annual peak sun hours, let’s calculate the required size of your solar system as a whole.
Calculate solar panel array quality and size
There is quite a range of solar panel performance levels based on quality. That means, higher quality translates into more power per square foot. Generally, individual solar panels vary between 150w to 345w per panel. It depends on the size and actual cell technology used to create each panel.
First, calculate the number of panels needed. Start by dividing your household hourly energy usage by the solar panel wattage. Do this for both low and high wattage options. To explain, this allows you to create a range of sizes. It’ll give you realistic expectations regarding available space on your property.
This will provide an estimate for the number of panels you need to generate adequate power. Then, a professional installer will determine the best angle for your solar panel array. Finally, your installer will determine how your solar panels should be arranged on your roof or other structures.
Solar inverter size calculations
Total household power loads are best handled by multi-mode inverters. They perform two primary tasks. As mentioned, it converts DC from the solar panel array and battery bank to 120V AC for the household electricity. On top of that, it charges and manages the battery bank charge levels to prolong battery life.
Multi-mode inverters backup very large household loads like air-conditioners, water pumps and heaters. Many of them provide high level of pass through power capability. Therefore, advanced solar power inverters don’t require separation of essential loads and non-essential loads.
Solar inverter sizes are rated in Watts. Installers use two primary factors to determine size. First, they calculate total power output of your solar panel array. Then, they calculate site-specific conditions – how much power your household uses.
The size of your solar panel array is the most important factor in determining the appropriate inverter size. As a general rule, the size of your inverter handle the DC rating of your solar panel array. If you’re installing a 6kW system, expect the proposed inverter to be around 6kW in kind.
Inverter manufacturers typically list sizing guidelines for solar panel array capacity inverters can be paired with. Find this info on their product specification sheets. Be sure that the size of your solar panel array paired with their inverter is within their stated guidelines. Otherwise, they may void their warranty.
Battery bank solar calculator
Since the sun doesn’t shine at night and many days will be cloudy, your battery bank must carry you through. Standard solar system sizing calls for three days of autonomy. That means, when no power is generated by your solar panel array, your battery bank will only be down to 50% State-Of-Charge (SOC) after three days. In practice, that works out to more than three days of storage.
Generators are for power backup when using an off-grid solar system. Standard sizing is the balance between your battery bank and the frequency you need to use that generator. During winter, your battery bank will sometimes fall short. Therefore, a generator is recommended to bridge those gaps in sunlight.
Now, calculate the minimum battery capacity in AH or Amp Hours. First, take the watt-hours per day and multiply them by three days. This represents a 50% depth-of-discharge on your batteries. Then multiply by two and convert the kWh result into AH. Just divide by the battery bank voltage (12V, 24V or 48V).
Solar system installation
First, do not attempt to install your own solar system unless properly trained, experienced, and correctly certified to do so. In other words, this type of installation is not a DIY project. To explain, solar component installation and wiring requires an electrician and a construction contractor to do it right.
For a comparison, installing a complete solar system is like installing a circuit breaker unit along with other major electrical systems. One primary component of a solar system is the solar power inverter, which powers your entire home. That means, safety and reliability is no different between the two.
Construction skills are also necessary to install a solar system. To elaborate, solar panel arrays are typically secured on top of existing structures. As such, the physical connections must be strong and reliable. Sometimes, structures are built from the ground up to carry the load of your solar panel arrays sufficiently.
To learn how to find the best solar system installer near you, check out the following article:
SOLAR INSTALLERS NEAR ME: How to pick a solar installer to do it right
