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How Much Solar Energy Can My Roof Produce

Net Metering Vs Feed In Tariffs

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Most utilities are required to offer what is commonly called net metering. Net metering means that your meter runs forward when you use power, and runs backward when you produce more than you use.

Some utilities offer a bonus for producing power, a feed-in-tariff. Madison Gas and Electric and Alliant Energy here in southern Wisconsin have this type of program. You buy electricity at the standard rate of 14 cents per KWh and sell what you produce back to them at 25 cents per KWh. This accelerates the payback time substantially for larger systems. The drawback is the initial cost is higher since the residence must have a second electric meter to monitor the amount produced. This could add $500-$700 to the initial cost because an electrician needs to replace the existing electric meter with a dual meter pedestal. As metering technology improves , this requirement could very well go by the wayside.

You will need to contact your local power company to confirm details on any programs they may have.

Looking For Solar Panels

Your minimum aim is to cover as much of your household consumption as reasonably possible for a typical day. If your power consumption is 30kWh on some days, but on most days it’s 20kWh, it might not be worth adding extra panels just to cover those few 30kWh days. You could go with a 5kW solar PV system and just accept paying for more power than usual from the grid on those occasional high-consumption days.

But solar panels are relatively cheap now, and there’s an economy of scale in installing a larger system, so it’s worth talking this through with your installer to consider how big a system you could get. Typical solar PV systems installed in 2021 are at least 6.6kW in size and we think that’s a good size for most homes to aim for right now.

That said, bigger systems of 810kW are becoming more common, especially for systems that include a storage battery.

You might think it’s better to oversize your system because any excess will be exported to the grid, and you’ll be paid for it via the feed-in tariff. But the feed-in tariff for new solar PV systems is generally very low typically from four to eight cents per kWh, though you can get better deals from some energy retailers and it’s unlikely on its own to justify the cost of a larger system.

Read more: Are solar feed-in tariffs worth it?

Power usage shifting

Online calculators

Final Thoughts On How Much Solar Power Do I Need For My House

The best advice is to reach out to an experienced solar panel installer. The average installer team does one or two home installations a day. Therefore, they will be able to see all the factors that would impact your specific site.

And now you know pretty much everything you need to know about solar power production and how much solar energy it takes to power your home. We hope you found this as enjoyable to read as we found it to write. Now go out, and enjoy the sunshine!

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Type Of Solar Panel And Efficiency Rating

High-efficiency panels can deliver more watts per square foot, which means you need to purchase fewer of them to reach your electricity generation target. There are three main types of solar panels: monocrystalline, polycrystalline and thin-film. In general, monocrystalline panels are the most efficient solar panels, followed closely by polycrystalline panels. Thin-film panels are the least efficient.

How Many Hours Of Sunlight Can You Expect In Your Area

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The peak sunlight hours for your particular location will have a direct impact on the energy you can expect your home solar system to produce. For example, if you live in Phoenix you can expect to have a greater number of peak sunlight hours than if you lived in Seattle. That doesnt mean a Seattle homeowner cant go solar it just means the homeowner would need more panels.

The Renewable Resource Data Center provides sunlight information by state and for major cities.

Now multiply your hourly usage by 1,000 to convert your hourly power generation need to watts. Divide your average hourly wattage requirement by the number of daily peak sunlight hours for your area. This gives you the amount of energy your panels need to produce every hour. So the average U.S. home in an area that gets five peak sunlight hours per day would need 6,000 watts.

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How To Understand All The Numbers And Symbols

Figuring out how much power youre going to get from your solar panel is actually a lot simpler than you might think.

Solar panels measure the power they collect from the sun inWatts . Typically, domestic solar panels produce a power output of between 250 and 400 Watts. Kilowatt is just another name for 1,000 Watts. We measure the energy a solar panel produces in Kilowatt Hours . So if you have a 250 W solar panel that gets the equivalent of four hours of direct sunlight a day, it produces 1 kWh of energy .

And then if you multiply your average daily power output by 365 , then you have your annual solar power output. In the example I used above, the yearly energy production would be 365 kWh.

Heres that calculation again:

Solar Panel Power in Kilowatts x Average Sunlight Hours Per Day x 365 = Annual Power in Kilowatt Hours

And thats it for the math.

The problem I have with all of this is that these numbers dont mean much to me until I translate them into actual energy usage. Why dont we take a look at what these Kilowatt Hours of energy mean to you and your electricity bill?

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Calculating Solar Power Costs

Once the above costs and benefits are determined, a solar system can theoretically be evaluated using the discounted cash flow method. Outflows at the beginning of the project would consist of installation costs , and inflows would arrive later in the form of offset electricity costs .

Rather than using DCF, the viability of solar power is usually evaluated by calculating the levelized cost of electricity , then comparing it to the cost of electricity charged by the local utility. The LCOE for household solar will typically be calculated as cost/kilowatt-hour – the same format commonly used on electricity bills. To approximate the LCOE, one can use the following equation:

LCOE = Net Present Value of the Lifetime Cost of Ownership / Lifetime Energy Output

The useful life of a PV solar module is generally assumed to be 25-40 years. The cost of ownership includes the maintenance costs, which must be discounted to find the NPV. The LCOE can then be compared to the cost of electricity from a utility remember, the relevant price is that which occurs during times at or near peak PV solar production.

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Is Your Roof Right For Solar

Solar panels work best when they get lots of direct sunlight. Depending on how your roof is set up and what direction its facing, it may be difficult to find a spot for solar panels that will maximize their efficiency.

Roofs with heavy trees or obstructions in place can make it hard for your solar energy system to produce electricity. For example, if your roof has a lot of trees paired with how closely the solar panels are to each other may make it difficult for any one panel to get direct sunlight. Solar panels can still produce electricity when theyre in the shade, but the efficiency will be significantly less.

Roofs that face different directions can also be problematic because theyll produce less electricity throughout the day than roofs with south-facing slants or more flat surfaces.

To determine how much solar panels will save for your home, take a look at how many hours of direct sunlight you receive throughout the day and how much shade is being cast on your roof by trees. Solar panels can be more worth the investment if you have an ideal layout to maximize the amount of sun they get.

Calculating Your Roof Space

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Before you know how many solar panels you need to meet your solar energy requirements, you have to find your roof space.

Step 1

To calculate your actual roof space, you need three measurements. The first is the height of the highest point of your roof to the joists , the second is the distance from the apex horizontally at joist level until the eaves of your roof , and the last is the length of your roofs apex .

Step 2

When you have these measurements, you will need to do some simple math.

The first formula you will need to use is:

A2 + B2 = X2

So plug in your measurements from above and solve for X. X is the distance from the apex to the edge of your roof.

Step 3

After this first calculation, you can use the result to calculate the overall area of your roof as follows:

C x X = area of roof

Multiplying C and X will enable you to find out the available roof space to accommodate how many solar panels you need. Then, deduct 30cm for the edge of your roof, as this area cannot be normally used to accommodate your solar panels.

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How Much Solar Power Can You Generate By State

Of course, there are many assumptions that we used that differ for every solar panel system. One of the major difference-makers is geographic location, which directly impacts the hours of quality sunlight your solar panel system will get. We used 5 hours per day as our average aboveheres how that number changes geographically, while still assuming an average roof size of 1,700 square feet and 320 watt solar panels:

How much solar energy can you generate on your roof by state?

State

*Assumptions: 17.5 square foot/320-watt solar panels, 5 sun-hours per day

Size Of Your Solar Panels

While there is a common size of solar panels, you still have to research your preferred brand and model measurements. This means that the number of solar panels you can fit on your roof can vary. For example, a Tesla solar panel wont be the same size as a solar panel from LG or Panasonic.

Pay attention to the specific measurements of your preferred brand, especially if you want to install the greatest number of panels you can fit on your roof. The average size of a solar panel is 78.74 x 157.48 cm. You can use this to calculate how many solar panels you can fit on your roof since each panel will take up approximately 1.3 to 1.4 square meters.

If you do not have enough space, you may need to invest in high-efficiency panels or those with higher power output. This way, you can install fewer panels and still cover your energy needs.

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How Many Kwh Can Solar Panels Produce And How Many Panels You Need On Your Roof

The amount of power your solar energy system can produce depends on the number of solar panels that can absorb solar energy and convert it into electricity.

Assuming you are going to choose standard-efficiency solar panels, here are the most common sizes for residential solar systems and their kWh production potential to give you an idea of how many panels you would need to run a house.

    • A 3kW solar system which consists of 12 panels can produce an average of 4,200 kWh per year. You will need a roof space of about 194 sq ft for a 3kW system.
    • A 5kW solar system which consists of 20 panels can produce an average of 7,000 kWh per year. You will need a roof space of about 340 sq ft for a 5kW system.
    • A 10kW solar system which consists of 40 panels can produce an average of 14,000 kWh per year. You will need a roof space of about 680 sq ft for a 10kW system.

Keep in mind that the amount of power your solar system can produce depends on how much sunlight your roof receives and your location.

For example, California has more sunny days annually than Washington. In this case if you live in Washington you would need a bigger solar system to get the same power as you would get with a smaller system in California.

The Renewable Resource Data Center provides average daily total solar resource information on grid cells by state and its free to use so check it out.

Solar Power Generation Choices

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The broad selection of solar panel models available for household use are not created equal. And, they do not all generate the same amount of power.

Solar panels are rated based on the watts they generate. The higher the wattage rating, the greater amount of power your solar installation will produce. Most residential solar panels have power output ratings from 250 to 400 watts, depending on panel size and how well they convert sunlight into energy. While higher power ratings are considered preferable, power output is not the sole factor in judging a solar panels performance.

For instance, two solar panels may each have a 15% efficiency rating, yet the power output rating of one is 250 watts and the other is 300 watts.4 The higher output may simply be due to the 300 watt panels larger physical size–rather than having a high efficiency or more advanced technology. Therefore, panel efficiency is a better indicator of solar panel performance than just power output for meeting your energy needs.

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What Financial Incentives Are Available For Solar Electric Systems

The US Department of Energy has Database of State Incentives for Renewables & Effciency . The DSIRE site has listings for federal and state for renewable energy as well as energy efficiency. Federal benefits are broken down to commercial and residential benefits.

For my system, I qualified for a 30% income tax reduction. This was after all other benefits and reimbursements are paid out. The 30% of the net cost will be deducted from your federal tax due. If the amount exceeds your tax liability, the remainder will be carried forward. To see current programs check out the dsire maps website.

In Wisconsin, I qualified for the state sales tax exemption for equipment purchased. Wisconsin Focus on Energy has a program for renewable energy. For photovoltaic systems the rebate was $600 per Kilowatt installed. My 1.8KW system returns $1080. My $9000 system cost me just over $5500. Another benefit is the property tax exemption. If you install a $20,000 system on your residence, the assessed value increases by the $20K, but the taxable value exempts the solar portion.

Research federal and state programs, they are changing regularly.

How Many Solar Panels Can Be Placed In That Area

Typically, that depends on the brand and model. However, most solar panels come in the size of 5.5ft x 3.33ft, which puts their size at 18.315sq.ft.

So, you can easily arrive at the total number of panels you can fit in 1,700 sq.ft. of area by dividing the total available roof area by each solar panels size, which comes to approximately 93.

Now, if you dont want to climb up the ladder and measure your roof area, then you dont have to. is uniquely equipped to do just that for you. It uses Googles powerful satellite imaging technology to calculate your roof area at the click of a few buttons.

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Connecting To The Grid

JEA customers who install solar PV systems at their home or business and connect to JEAs electric grid must apply for JEA’s Distributed Generation Program. An application form must be submitted and approved by JEA prior to beginning installation or construction of any solar PV system.

Commercial customers who are considering installing a distributed generation system 60 kWDC or greater may be subjected to JEA Standby and Supplemental Service rate.

Solar Panel Output Per Square Meter

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The most common domestic solar panel system is 4 kW. And it has 16 panels, each of which is about 1.6 square meters in size. They are rated to generate approximately 265 watts of power .

To calculate the output per square meter, you can use the following formula:

  • Number of panels x Capacity of the solar panel system
  • Capacity ÷ Total size of a system

Also, you have about two different ways to calculate the power production that you might get from your solar panels at home. They are mainly related to how much power you need and how many square meters of roof space they will account for.

You have two options: easy and rough way accurate and complex way.

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How Much Do Solar Panels Save On Energy

Solar panels come with massive benefits both in the money that they save homeowners and the sustainablegreen energy they produce.

Many homeowners wonder how much solar panels will actually help you save on electricity use and cost. However, because they are expensive to purchase and install on a home, its important that the benefits outweigh the cost of investing in them.

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