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Grid-Tie Basics

1. What is a Grid Tie Solar Electric System?
2. Why Install a Grid Tie Solar (PV) System?
3. On Grid or Off Grid?
4. How Does a Solar Grid Tie System Work?
5. Sizing Your Grid-Tie Solar System
6. How Much Power Do I Need?
7. Major Solar Grid-Tie System Components
8. How Much Will My Grid-Tie Solar System Cost?
9. Which Brands and Products are the Best?
10. System Payback
11. Incentives

1. What is a Grid Tie Solar Electric System?
A grid tie solar electric system - also referred to as grid-tied or utility intertie photovoltaics (PV) - uses solar panels, a power inverter and other components to turn sunlight into electricity for your use, while your home remains hooked up to the local utility. This is different from an off-grid or stand alone solar system, where your structure is not hooked up to utility power.

2. Why Install a Grid Tie Solar (PV) System?
The most common reason people install a solar grid tie system is to reduce their utility bills. Once your system is operating the power it provides is free, and there is little or no maintenance required. While it runs, your PV system reduces your electrical bills, not only because it decreases how much power you pull from your utility, but also because any excess power you produce is pushed back into the grid (net metering) effectively turning your meter backwards. Eventually your PV system will pay for itself, but your energy savings will continue long after.

In addition to what you save on your electric bill, having a grid tie system raises the value of your property. Solar also makes a home more attractive to potential buyers, particularly when compared to an otherwise identical home. This can make a big difference should you decide to sell your home in a tight real estate market.

Another great incentive for installing solar is that the Federal government, and many states and local utilities, offer rebates, tax credits, low interest loans and other incentives for adding solar power. Please see our Incentives information under Learn More, or give us a call to find out about programs for which you may be eligible.

And of course, solar energy is a clean source of power. It reduces dependence on fossil fuels in a practical and effective way, and helps protect our environment.

3. On Grid or Off Grid?
Fire Mountain Solar never recommends that a customer who is already hooked up to utility power disconnect and go off-grid. There are many reasons, but some key ones are:

  • Grid tie systems are less expensive than off-grid because they require no storage batteries.
  • Off-grid solar has some unique design limitations, which means most people will need to adjust their power use habits and may need to replace some appliances (such as an electric furnace or electric oven) to make an off-grid system practical and cost effective.
  • Batteries, which are necessary in off-grid systems to provide power at night or at other times when power is not being produced, can be expensive and they require regular maintenance. They also have a shorter life expectancy than most other solar system components, which means that they not only add to the upfront cost of a system, but they add to the costs over time because batteries need to be replaced "regularly".
  • And, on-the-grid solar systems offer you the best of both worlds. You can have your system sized so that your 12 month average electrical bill next to nothing, but still have the flexibility to at any time draw more than your solar array is producing without having to do a thing.

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4. How Does a Solar Grid Tie System Work?
When sunlight shines on solar panels they produce Direct Current (DC). That DC electricity is converted into household AC power by your power inverter, and it is then available for household use. This process happens silently and automatically every day.

When a grid-tie solar electric system generates more power than you are using in your home, the excess electricity is sent out into the utility grid. The excess power going into the grid spins your meter backwards, allowing your neighbors to use clean, quiet solar power. If you use more power than your system is producing, your inverter will automatically pull the needed power from the utility grid - and you'll never notice a thing.

This is back and forth process is called "net metering", and it means you are only billed for the "net" electricity purchased over the entire billing period. At the end of each billing cycle your meter will not have spun as far forward when compared to not having solar electricity, saving you money. If you produce more than you use during a billing period, your utility company will retain it as a credit, which will then be applied to future electric bills.

5. Sizing Your Grid-Tie Solar System
Grid-connected PV systems are typically sized to eliminate part of your electric bill because of the higher upfront costs associated with purchasing a larger system. However, larger systems will cost less per kilowatt-hour generated due to the economies of scale associated with manufacturing processes. The utilities have adopted a rate structure that increases the cost of electricity as you use more of it. Many people choose a system that will only eliminate the most expensive electricity. This increases the return on your investment.

6. How Much Power Do I Need?
Sizing your solar grid-tie system is not as complicated as you may think. With only an electrical bill, you can determine the minimum system size you'll need. Once you've determined that, you can determine how many solar panels you'll need, and find compatible components from there.

To begin, you'll need your 12 month average electrical use-which you should be able to find on your utility bill. This number will be in kWH (kilowatt-hours).

If you have not been in your home for a full year try one of the many online calculators for estimating your power use.

Then follow these steps to get a ballpark estimate of your minimum system size:

  • Record average monthly kWH electrical use: __________kWH
  • Multiply this by the percentage you want the solar system to produce: __________kW (ie: 1000kWH X 50% = 500kWH)
  • Divide by 30 for the daily output from your solar power system: __________kW
  • Divide by the daily average sun hours for your location: __________kW (Refer to the Sun Hour map for daily average sun hours for your area below)
  • Divide by 75% to compensate for system efficiency: __________kW

US Sun Hour map for daily average sun hours

Once you know how large of solar array is required to meet your power demands, you can select the appropriate products. Here is a list of some of the Major Solar Grid-Tie System Components you will/may need:

7. Major Solar Grid-Tie System Components

Solar Panels

Solar panels absorb solar energy from the sun and convert it to DC power. Your power consumption, as well as your geographic location, affects the type and quantity of panels you will need. Because each solar panel only produces a small amount of energy, most solar electric systems consist of multiple solar panels interconnected together in "strings". This is called a PV (photovoltaic) or solar array.

Solar Panel Mounts (Racks) and Solar Trackers

Solar panel mounts are important to provide proper directional and latitudinal orientation, maximize production, and to provide the stability needed to protect your investment from the force of the wind. Solar panels can be mounted on the roof, ground, or on a pole.

A solar tracker is a device for orienting a solar panel or solar array toward the sun. Solar trackers increase morning and afternoon exposure, which at the right latitudes and in the right climates can substantially improve the amount of power produced by your system.

Power Inverter
A power inverter converts the DC power from your solar panels and other renewable energy sources into AC power for your use. Power inverters for battery-based systems may include a solar charge controller.

Grid Disconnect

A grid disconnect allows you to stop the flow of electricity between your solar panels and your electrical system. This provides for the safe maintenance of electrical and utility systems.

Combiner Box

This box gathers all of the solar panel connections at one location, providing a neat, clean looking installation.

DC Disconnect

Your array's DC disconnect safely shuts down your solar power system at a moment's notice, allowing for safe maintenance, repair, and inspection.

8. How Much Will My Grid-Tie Solar System Cost?
The number of solar panels you need and how you want to mount them are just two of the factors that will affect the overall cost of your off-grid system. Another important factor will be which brand of products you choose.

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9. Which Brands and Products are the Best?

The number of companies offering solar equipment is rapidly increasing. And each solar professional you speak with will have certain products they recommend, and they usually have very convincing reasons for recommending those products. This can make it a challenge for consumers to know whose opinion to trust, and which products are truly the best.

So how do you choose? As with any major purchase, you will want to do your homework. With all the focus on renewable energy, it is easier than ever to get reliable information on manufacturers and specific technologies, but this can also leave you with an overwhelming pile of information to sort through.

Our best suggestion is to find a solar professional you trust, and allow them to guide you through the ever-changing maze of renewable technology. And then we suggest you get a second opinion. Because renewables are a major investment, it is always a good idea to talk with more than one professional to be sure you are receiving information that is accurate, pertinent and complete.

Once you have recommendations on products to choose, you can also do some research online to see what others are saying about those products. Check out each manufacturer's website or give them a call. Check out one of the many industry blogs, the Better Business Bureau (BBB), and industry publications. (Remember, the manufacturer will naturally tell you the best about their products, so don't rely solely on the information they provide to make your decision.) Because of the increased demand for renewables, third party testing agencies such as Consumer Reports are also starting to offer consumers with quality information.

From our experience, here are some things you'll want to consider as you're shopping for products and choosing brands:

How long has the manufacturer been making renewable energy products?

There are a plethora of new companies getting into the industry, and we have found many of them use "the new math" when they calculate their industry experience. Don't just take their word for it - ask around to find out if they really know what it takes to make good products.

What is the track record of their products?

Ask around about a manufacturer's reputation and about how their products perform in the field. You can find online sources for this information, or you can talk with consumers who are using their products.

Is it proven technology, or will you be "field testing" something new?

So first we look at who is introducing the product. We are much more confident when trying out something new from the industry leaders like OutBack Power, SMA, Xantrex, Sharp Solar or BP Solar, than we are about trying something from XYZ Company, who we have never hear of. It doesn't mean XYZ's product isn't good, it just means that we don't have history with them to rely on. We know that OutBack, etc., will be there should their product not perform as they've expected, and we know they will make it right. We don't know if XYZ Company will.

Another reason we are cautious is because sometimes a technology is so new there is insufficient field performance data for us to be confident recommending it.

Another thought about new renewable energy technology: It often seems that the marketing and sales folks get all excited and start talking about new products that are either in the early stages of research and development and/or far from actual production. The most common one we hear about is new solar panel technology that will cost almost nothing and make gigawatts of power. So far, (unfortunately) none of those products have actually shown up in the market.

Is it the right product to do the job?

Sometimes you may hear of a couple of different products that have proven track records and that are made by reputable companies. So how do you know which one is right? Obviously the first consideration is whether or not they will do the job you need them to do. Again our best recommendation is to talk with the professionals, or at least chat with folks who are using the different products, to get their thoughts on the subject. Assuming each of the solar products you're considering will do the job, then it naturally comes down practical details such as price, warranty, and extra features.

Which products does your solar contractor use at their home and/or business?

This is a great question to ask. It not only tells you something about the products, but also helps you determine if your solar professional has practical experience with the products they sell.

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10. System Payback

Payback is usually used to describe the time it takes for an