Saturday, March 23, 2024

How To Calculate Solar System Size

Actual Energy Use Quote

How to Size your Solar Power System

Use this solar calculator to determine a precise system size for your actual energy use.

The NEXT STEP, now that you have an estimate for the desired kW, VIEW SOLAR KIT SIZES to compare prices, brands and, options.

Remember, you decide how much solar to get based on the need, available space, and budget. There is no rule that you have to offset 100% of current energy use. Utilities will generally allow grid-connected systems up to 120% of the previous 12 months consumption. They will also allow for consumption increases from an electric vehicle, home expansion or other needs.

Battery Capacity For Inverters

Now that you understand the different ways to calculate battery capacity, its time to put this information into practice.

For example, you want to power a refrigerator that consumes 200 watts and has an amp hour rating of 100. You will need to do the following:

  • Calculate the load in watts: 200 watts
  • Convert amps to watt-hours by multiplying amps by hours: 100 amps * 100 hours = 10000 watts-hours
  • Convert watt-hours to kWh by dividing the total watt-hours by 1000: 10000 watts-hours / 1000 =
  • The battery capacity required for this inverter is: 11 kWh

When sizing a battery bank, its important to remember that you will need to round up the battery capacity required by the inverter. In this example, the battery bank would need to be 12 kWh.

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The Home And Site Evaluation

In the design phase, the solar installer will evaluate your home to determine the best solar panels, inverter, racking and other components. SunPower dealers often recommend our SunPower Equinox platform, an integrated solar system that combines SunPower® solar panels, micro-inverters and other components all covered under SunPowerâs industry-leading Combined Power and Product Warranty. Other installers will design systems with components that may come from several different manufacturers, all with different warranty terms and services.

As part of the evaluation, your solar installer will make an appointment to inspect your attic, your roof and your homeâs electrical system. He or she will determine the best location to mount the hardware that runs your system . During the inspection, the installer will evaluate your property to ensure that the installation is code compliant and will recommend upgrades if required. For example, if you have an older home, your electrical panel may need to be updated, or when inspecting your attic or roofing, the installer may discover issues that require repair before your system is installed.

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The Climate Of The Area And Peak Sunlight Hours Calculation

The sunlight hours available to your location will directly impact the watts generated from the solar set up.

The more hours of sunlight available the less number of panels required to generate a given output.

Inversely, with lesser sunlight hours, more solar panels will be required. By dividing this average hourly wattage requirement by the number of sunlight hours daily at the location, you calculate the watts your panels need to produce every hour. Using this figure you can select the panels required. The sunlight hours and sun angles vary by season. This will also be a factor for calculating the number of available sunlight hours and thus the panels required.

Lets look at a simple calculation to understand this concept better.

Lets say the summer season sunlight at the location is available for 6 hours and for mid winter it is 4 hours. Then in mid winter a 10w panel will provide 10w * 4h = 40watt-hours of DC power into your battery. In summer the amount would be 10w*6= 60watt-hours. There would be a little energy lost due to resistance through the regulators, cables, and batteries chosen. In calculating the solar power system you would built some assumption of loss into the final calculation.

How To Calculate Home Energy Consumption

3 Easy Ways To Calculate Solar System Size For Your Home

You could add up the wattage of all your appliances and estimate how many hours they are used each day, but this is very cumbersome and not accurate.

For example, some appliances, such as refrigerators, are difficult to estimate. This is because they have compressor motors on board and have variable instantaneous power values.

By far the easiest way is to take it from last years utility bill, which normally shows the full years energy consumption in kilowatt-hours .

Simply divide this figure by 12 to get the monthly consumption, or 365 for the average daily consumption.

The average amount in the US is about 30kW per day, but your own will depend on where you live.

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Home Energy Audit Example

Let’s say the average monthly kilowatt reading on your electric bill was 300 kwh. Divide 300 by 30 = 10 kilowatt hours per day. If you have an average of 6 hours of full sunlight per day, you would then divide 10 by 6 = 1.67. Then multiply by 1.5 = 2.5. And finally, multiply by 1000 to convert to watts.

2.5 x 1000 = 2500 watts of power is needed per hour to meet all of your energy requirements.

Your solar system will need to produce 2500 watts per hour.

Even if you don’t plan to create this much energy, you should still use this method to determine how much power you would need, so that you have a clear idea of what to eventually strive for.

How To Calculate Your Solar Panel System Size

One of the most common questions we get from our customers pertains to how to calculate their solar panel system size to meet their energy needs. Matching your solar panel system design/configuration to match your energy usage will produce maximum cost-efficiency.

Lets explore how to calculate your power needs, how to estimate power output from solar panels, and how to reconcile those to find the right size system for your home or business.

Bear in mind that theres a little bit of math involved but well provide some online tools to make the calculation work as easy and accurate as possible.

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Calculate Your Kwh Usage

  • Gather the kilowatt-hours usage from your electric bill. Youll want to have full 12 months of usage to be able to look at peaks and valleys in usage over a year. Energy consumption spikes in the summer and winter with heavy use of your A/C and heating units.
  • Determine your average monthly kWh usage. Add up your kWh usage for 12 months and divide by 12 to figure out your average monthly consumption. Your grid-tied system will tend to overproduce in the summer with peak sun exposure.
  • Figure your daily kWh usage. Divide by 30 to determine your daily kWh usage.
  • To determine your homes energy usage more accurately, use our home appliances power consumption table to find out how many kWh your appliances would use per month.

    If your utility provides a favorable net metering policy, the energy your system generates can be banked with the utility as a credit that can be used later. Not all utility companies give you credit check with your local provider.

    How To Use Pv

    Solar System Calculation For Home / Inverter battery solar panel requirement / 350w Calculation

    The previous section assumed that you can mount solar panels at an ideal location: Perfectly south facing, with a great tilt-angle, and without any shading. What if your roof, or other location, is not quite that good? In most cases we can still accurately figure out what it will take to produce the kWhs needed. All we need is a little help from the US tax payers!

    The US government, and NREL in particular, has created a very handy online tool that can calculate solar PV yield for any place on earth, taking orientation, angle, and even the local weather patterns such as cloud cover into account. It is called PV-Watts and clicking this link should open it up in a separate window. First we enter the location of the solar panels, or Ottawa to stick with our previous example. PV-Watts now finds the nearest location that it has weather data for, and displays that. Go to the next screen, and for our example we need to change a few parameters. The DC system size is how much solar PV you have, in kW. We want to know what each kW of panels will produce so change this to 1. The module type of Standard should be fine for most, we can also leave Array type to the default of Fixed . The system losses of 14.08% are fine too. For the Tilt we will change this to 45 degrees, the latitude of Ottawa, just like our earlier example, and the Azimuth is fine at 180 degrees .

    Correction factor = PV-Watts reported yield per kW of panels / Actual yield per kW of panels

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    Why Use Peak Sun Hours

    Sunlight varies in intensity by location and time of day. The sun shines more intensely at 1pm in Arizona than it does at 8AM in Alaska.

    So if we were just to measure the length of time sun shines on a solar panel, it wouldnt give us a very clear idea of how much energy that solar panel generated during that time. We need to know how intense that sunlight was.

    Plus, we can use historical data to predict how many peak sun hours a location will get on an average day. These predictions help when picking what size solar panel or system to use.

    Solar In North Carolina

    North Carolina ranks 4th in the U.S. for solar adoption as of Q1 of 2022, according to a report from the Solar Energy Industries Association . In simple terms, there are enough installed solar panels to power practically one million homes. In terms of solar production, North Carolina ranks 5th, according to a SEIA 2021 Year in Review report.

    A benefit of living in NC is that we receive more sunny days per year than the national average so thats some awesome news for us solar-lovers! The average solar panel system size for areas in North Carolina is 6.5kW to 8.5kW.

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    How Many Solar Panels Do You Need To Power Your House

    Example Calculate Solar Panel Size

    How manysolar panels and their power rating would be needed for a fixed solar system to cover the energy consumption of an average U.S. home?

    Lets say the house is in Burns, Oregon USA, with an average electricity consumption per day of 33 kWh.

    Checking the site Global Solar Atlas, we see that the irradiation in this location is 5.83kWh/m2/day.

    Use historical irradiance data to find suns energy in your location

    • Geographic Location: Burns, Oregon, USA
    • Average daily energy consumption: 33kWh/day
    • Irradiation for Burns, Oregon is 5.83kWh/m2 per day

    PV System Losses

    I previously said that system losses can be 23%, but they can also be higher. Ill use 30% as the overall system loss, to make sure I dont underestimate the number of solar panels to cover the homes energy needs.

    With 30% losses in mind, the energy needs are:

    33kWh/day x 1.44 = 47.5 kWh/day load.

    Now to take into account the efficiency of inverter, which is about 96%.

    The power to be supplied to the inverter = 47.5/0.96 = 49.5kWh/day.

    The average daily irradiation is 5.83kWh/m2

    49.5kWh/day of power can be produced by:

    49.5/5.83kWh/m2= 8.5kW or 9kW of solar panels working at 100% capacity rating.

    To find the number of solar panels needed, divide the wattage needed by wattage of each solar panel :

    Number of panels needed = 9kW/300 watts per panel = 30 solar panels.

    Financing Your Solar System

    Solar sizing calculator excel

    The easiest and most profitable way to finance your solar system is to use your 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. For example, you can use ahome equity line of credit or any othersecured loanas unsecured loans have high-interest rates and likely make a solar energy project in Canada non-economic.

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    How To Calculate Solar Panel Output

    Heres a simple formula for calculating your solar panels power output.

    Solar panel watts x average hours of sunlight x 75% = daily watt-hours

    As an example, lets say you have 250-watt solar panels and live in a place where you get 5 hours of sunlight per day. Whats that 75 percent for? Thats to account for all those variables weve been going over.

    250 watts x 5 hours x .75 = 937.5 daily watt hours

    To translate this into the more familiar kilowatt hours youre used to seeing on your electricity bill, simply divide by 1000.

    937.5 / 1000 = 0.937

    To round up and make it pretty, thats 0.94 kilowatt-hours per solar panel.

    Of course, you dont have to do this math yourself. Vivint Solar experts will help you through these calculations to find the optimal solar panels for your home. We do this every day and we think its fun. Since we get a lot of questions about how to calculate solar panel output, we decided to share it with you.

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    Dont Overcharge Your Batteries

    Once you have sized your battery bank and solar panel array, determining which charge controller to use is comparatively straight forward. All we have to do is find the current through the controller by using power = voltage x current. Take the power produced by the solar panels and divide by the voltage of the batteries.Example: A solar array is producing 1 kw and charging a battery bank of 24V. The controller size is then 1000/24 = 41.67 amps. Now introduce a safety factor. Multiply the value you have found by 1.25 to account for variable power outputs: 41.67 x 1.25 = 52.09 ampsIn our example we would need at least a 52 amp controller. The Flex Max 60 MPPT Charge Controller would fit our specifications.

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    Inverter Sizing For A Grid

    Inverters for grid-tie solar systems are simply sized to take maximum advantage of the solar output. In practice this means the inverter can be undersized to around 85% of the solar PV array size without much penalty in energy production. Even for a perfectly south-facing solar array. Solar panels rarely produce rated output, you will see that happen just a few times a year, usually in early spring when it is still very cold outside, with a clear-blue sky, and the sun already high in the sky at noon. The rest of the time solar panels will produce less, much of the time a great deal less, than their rated output.

    For solar arrays that are less-than-ideal, it may be possible to undersize the inverter even more, without a penalty in annual energy production. That is something that needs to be evaluated on a case-by-case basis.

    It is important to keep in mind that inverters do not need to be the same size as the solar array. This is an area where potentially some money can be saved so there is a better payback period for the solar system, and resources are better utilized.

    For our sample solar system of 9.25 kW of peak-power in solar modules this means:

    9.25 x 0.85 = 7.9 kW inverter size is sufficient

    Fronius makes a nice 8.2 kW string inverter, that is the next size up, and it would be a great choice for this system!

    Determine Solar Charge Controller

    Solar System Size Calculation | RENVU

    All solar power systems with batteries as backup should include a Solar Charge Controller to prevent the batteries from overcharging and also to prevent the batteries from sending their charge back through the system to the solar panels during times of low sun, .

    Since a solar controller does its work in line between the solar panel array and the storage batteries, it makes sense that its selection and sizing is influenced by those components.

    Voltage and current are the two parameters used in solar charge controller sizing. The solar controller must be capable of accepting the maximum power produced by the solar panels while delivering the proper DC voltage and charging current to the batteries.

    For systems in continuous operation the industry standard 1.2 de-rating factor is specified to prevent the controller from becoming damaged due to excess solar panel current or power. The solar panels above have a short circuit current of 6.20A. The solar charge controller rating will therefore be: 4 solar panels with rated current of 6.20A each = 4 x 6.20 x 1.2 = 29.76 A or 30Amps. So the solar charge controller like the one on the left should be rated 30 Amps at 12 V or greater.

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    Factors That Affect Solar Panel Power Output

    Aside from the most obvious element available sunlight the following factors affect solar power output:

    • Available roof space. The roof is the ideal location because it is the most cost-effective, usually the most sun-exposed, and the easiest rack to install. But if you dont have enough roof space to match your energy needs, alternative mounting options may be viable.
    • South-facing roof space. Roof space facing southward captures the maximum amount of sunlight throughout the day. If you dont have south-facing roof space, you will need extra solar panels to make up the difference.
    • Solar panel efficiency

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