Solar Panel Capacity
Approximate Number of Panels
Approximate Area of Panels in Square Foot
Approximate Solar Panel Cost
Approximate Solar Panel Cost After Federal Tax Credit
What You Should Know
- The main components of a self-sufficient solar system are solar panels, charger, battery and inverter.
- Connecting a solar system to the grid reduces the components needed in the system and thus the capital cost of your solar project.
- Main components of a grid connected solar system are electric current inverter and solar panels.
- The federal government currently offers a generous tax incentive equal to 26% of what you spend on installing a solar system.
- There are many options for financing solar systems.
- In many instances solar systems are sound financial investments in addition to being the right choice for the environment.
How Does the Solar Panel Calculator Works
Judging Your Electricity Need
To know how much energy you want your solar system to produce, we need to multiply your electricity consumption by the percentage of electricity you want to source from the sun. So we ask for your monthly electricity consumption, and multiply it by 12. Electricity consumption is usually measured in kWh. In this abbreviation, the letter k stands for kilo, meaning 1000; W stands for Watt which is the unit of power in the international system of units. Watt is defined as 1 Joule per second. Finally in kWh, the letter h stands for hour. When you multiply power by time the result is energy. If you don't know your average monthly electric consumption, input your monthly electricity bill. We use the average cost of electricity in your state to calculate your electricity consumption. If you don’t remember your monthly electricity bills either, the default value is the average monthly electricity consumption in your state.
Judging Your Solar Installation Capacity and Size
The amount of electricity produced by your panels at each point in time depends on the amount of light they receive which in turn depends on the intensity of light and the angle it makes with the solar panel surface. Each of these factors are constantly varying. Thus we make the approximation that the panel produces 75% of its nameplate capacity during sunshine. Thus this calculator divides your required electric energy by your annual sunshine hours and by 0.75 to calculate the solar capacity you need.
There are solar panels with various capacities. Solar farms commonly use larger solar panels with higher capacity compared with residential solar installations. Each solar panel consists of a number of solar cells serially connected to each other. Residential solar panels typically consist of 60 solar cells while industrial solar panels typically consist of 72 solar cells. Residential solar panels in the US market average a nameplate capacity of 355 watts. So by dividing your required solar power capacity by the number 355 we derive the approximate number of required solar panels.
Residential solar panels are typically 65 by 39 inches. Thus the required area for installing panels is the number of panels times 17.55 square foot. One of the most important points to consider when assessing the viability of solar power for your residence is if you have an appropriate surface for installing your solar panels.
Judging Your Solar Installation Cost
The cost of your solar project scales with your power requirement, but this scaling is not linear. The larger your project, the lower your per watt cost would be. This calculator is using the average cost for solar systems with a capacity close to your required capacity.
Incentives For Installing a Solar System
If your solar system was placed in service before the end of 2019, you could have claimed a federal tax credit equal to 30% of what you spend to install your solar system and bring it to service. In other words, depending on the amount of taxable income you had you could have got up to a 30% discount on your solar system in the form of a cash back rebate from the Federal government. If your solar system is placed in service from the beginning of 2020 to the end of 2022, you can claim 26% of your solar cost as a Federal income tax credit. So that is like a 26% rebate. If your solar system comes online any time during 2023, you can get back 22% of your solar system cost in tax incentive. This incentive is known as investment tax credit (ITC). In addition, many state governments, local governments and even utility companies have incentives in place to sweeten your solar system.
Positioning a solar system
First point to consider is that the installation site for solar panels should be free of shade. Maximum irradiation is received by panels when they are perpendicular to the incoming sun rays. So to get maximum power, solar panels should face south. But as peak electricity use is in the afternoon, electricity produced in the afternoon is more valuable compared with electricity produced in the morning. Thus panels facing west would produce less but more valuable electricity. Thus only parts of your roof facing in a direction between south and west are suitable for solar installation. You need to make sure you have more than the required roof surface in the appropriate direction. Furthermore, it is best for your solar panels to tilt toward the equator by as much as your latitude.
Financing Your Solar System
The easiest way to finance your solar system is to use your own savings and replenish your savings by using the money you would have paid for electricity bills otherwise. At the end of the payback period you would have free electricity just by keeping your solar system clean as you keep other parts of your home clean.
If for any reason you prefer not to use your cash there are many options available for financing your solar project. One of your options is PACE or Property Assessed Clean Energy also known as the Home Energy Renovation Opportunity (HERO). With PACE a financial institution pays for your solar installation, the local government increases your property taxes over a 20 year period and uses the added proceeds to pay back the financial institution. This program, which operates in more than 20 states, reduces financing cost by removing risk from the loan.
What Constitutes Your Solar System
A sine wave. In this graph the vertical axis denotes
voltage and the horizontal axis denotes time.
Solar panels under radiation produce direct current (DC) electricity; but our appliances are designed to use alternating current (AC) electricity. Thus to use solar panels, we need an electric converter to transform DC current into AC current. Mains electricity or utility power exhibits a sinusoidal form. You want to connect your system to the grid so to give extra power to the grid at peak production (typically a short while after noon) and to get power from the grid when you don’t produce electricity. Thus use of a fairly complicated grid interactive or synchronous inverter is necessary. This grid-tie inverter is required to match the voltage, frequency and phase of your solar produced electricity with that of the utility grid. Also your inverter is required to shutdown automatically in case of blackout. Currently there are few inverter technologies commercially available.
A solar inverter is being tested.
Apart from inverters being an important and sensitive part of your solar system, solar panels themselves are not all the same. Solar panels are made of the semiconducting element silicon. This element is the second most abundant element on earth. It can be found in the form of silicon dioxide, for example in sand. But reducing silicon dioxide to elemental silicon and purifying the resulting silicon is very energy intensive and costly. The larger the silicon crystals are higher would be their efficiency in capturing light photons. Solar panels made of solar cells which are in turn made of very large silicon crystals are called single crystals. They offer higher efficiency and are sold at a premium in price.
Solar panels do not have moving parts so they don’t have wear and tear. If your solar panels are made by a good manufacturer you are likely to get 25 years of guarantee. If the manufacturer feels comfortable guaranteeing their product for 25 years they are likely to work for 50 years and you would have many years of free electricity after your payback period.
Sources of Energy
It is interesting to consider the energy sources used to power human activities in 2020 in the table below:
|Share of different energy sources in some economies (in % of total energy used)|
Data from “Our World In Data” project.
As we see in the table above the lion's share of the energy satisfying human needs are sourced from fossil fuels, namely, Oil, Coal and Natural gas. These were created millions of years ago by living organisms. Plants, algae and many bacteria engage in the process of photosynthesis. They use the energy from light (electromagnetic waves) coming from the sun to combine carbon dioxide and water and produce organic matter needed for their growth and reproduction and release oxygen by-product into the atmosphere. Their corpses buried deep underground have transformed into what we call fossil fuel.
Over the past few hundred million years living organisms engaged in photosynthesis have gradually transformed the earth's atmosphere. Initially most of the oxygen they produced oxidized the methane in the atmosphere. Depletion of the atmosphere from methane caused the haze to clear and blue skies to appear. Photosynthesis continued to get carbon dioxide out of the atmosphere and put oxygen into the atmosphere. This gradual reduction in greenhouse gasses (methane and carbon dioxide) slowly cooled the atmosphere. This effect was partly countered by the rise in the sun's temperature and shine. The final result is the present climate of the planet earth being suitable for human habitation.
Still the climate is very complex and variations in it occur. The tilt of the earth toward the sun might change or the ocean current might change or a very big volcanic eruption or large meteorite impact can each start the process of significant changes in the climate. Indeed over the last two million years there have been a number of glacial and interglacial periods. Transition between a glacial period and an interglacial period entails a 4 to 7 degrees celsius, or a 7 to 13 degrees Fahrenheit, change in the average temperature of the earth. Such a change has occurred over a period of about 5000 years. Such a rate of change allowed many organisms to adapt themselves to the changing conditions and avoid extinction. Climate models predict a change in the average temperature of the earth between 2 and 5 degrees celsius. This change is far faster than past global warmings and coolings. Likely many living organisms would not be able to adapt to the changing climate and a mass extinction is likely to occur. Thus your action for reducing the severity of this change is commendable.