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Grid-Tied Solar Interconnection Options
Nov19

Grid-Tied Solar Interconnection Options

If you are installing solar to save money on your electric bill, it is going to be a “grid-tied” system. When we talk about the “grid” we are talking about the electric company’s network of transmission lines and equipment that bring the electricity from the power plant to your house. The “tied” part of “grid-tied” means exactly what you would think it does, you are going to connect your solar power system to that grid.  The actual point of interconnection is typically your main service panel. This is the point where the grid ends and your home’s electrical system starts. It can generally be said that anything before your main service breaker belongs to the electric company and we call this part of the system the line side or supply side. Anything after your main service breaker belongs to you and we call this the load side because that is where your loads are. A load is anything that uses electricity like your lights, washing machine, air conditioner, etc. There are a few different ways to make that interconnection at the main service panel and that is the point of today’s article. The simplest method for the do-it-yourself solar installer is a load side connection made with a circuit breaker in your main service panel. This means you are going to add a circuit breaker in your main service panel next to all the circuit breakers that feed your loads and you will connect your solar inverter output to that circuit breaker. One thing to note about this type of load side connection are that the inverter circuit breaker will need to be as far as possible from your main breaker so you may have to move a few load breakers to make space for it at the end of the busbar that holds all your breakers.   Another thing you need to know about a load side connection with an inverter circuit breaker is that you have to follow the 120% rule (2014 NEC 705.12(D)(2)(3)(b) or NEC 2017 705.12(D)(2)(3)) where the main service breaker plus 125% of the maximum solar output must be less than or equal to 120% of the busbar rating. You can see our previous article about evaluating your main service panel for solar to understand the math on this but the bottom line is there are times when you can’t make this type of connection without an expensive main service panel upgrade, so let’s look at the other options that are available.  So, if you are not going to interconnect your solar power system on the load side of your main service breaker, that means...

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Is Your Roof Right for Solar?
Nov15

Is Your Roof Right for Solar?

If you look around, you are likely to notice that more and more roofs in your neighborhood are getting filled with solar panels. Which makes sense because all those homes use electricity and the solar panels are going to save those homeowners lots of money. But not every roof is the ideal place for solar so let’s talk about what makes a roof right for solar. First, the weather where you live will make a difference in your solar output, but even places where it rains a lot like Portland get enough sun for solar to make sense. If you are getting a solar production estimate, it is important that you use the correct zip code so you get an accurate estimate, but any location is going to have enough sun to save you money. The next thing to look at is the orientation of your roof. Solar panels produce the most power when the sun is hitting them directly. While you may think that north-facing roof looks bright and sunny, the sun never hits it at a direct angle and it is not a great place for solar panels. But sometimes people do install solar on the north facing roof so let’s get into some details on this. In the continental United States, solar panels facing South at about a 30 – 40 degree tilt angle will produce the most electricity annually. If you are in the southern states, the lower angle is better because the sun is higher in the sky. If you are in the northern states, the steeper tilt angle is better because the sun is lower in the sky.  If your roof is not quite facing due south but it’s close (within 30 degrees of south on a compass), it will still produce almost the full amount of power. If it is facing east or west you will lose about 15% – 20% of the annual production. The steeper the roof is, the more you will lose. So if the roof is pitched 10 degrees to the west, it will only be a 15% loss but if it is at 35 degree pitch to the west it will be more like 20%. A north facing roof will be a 30% – 50% annual loss depending on the pitch.   The pitch also matters on a south-facing roof 30-40 degrees is ideal for annual production and a roof that is totally flat will be at a 10% loss in the southern US and a 15% loss in the northern US.    Now, there are times where annual production is less important and you want to optimize production...

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3 Big Benefits of Microgrids
Nov11

3 Big Benefits of Microgrids

Wildfire season in Southern California has become synonymous with rolling blackouts for homes relying on grid power, shinning the spotlight on microgrids as one of the best solutions to providing the state with its energy needs and spurring a significant increase in inquiries about solar + storage.  Solar microgrids work as a localized source of energy generation, which is connected to a more extensive energy network, but can disconnect, or “island off,” from the system.  While numerous benefits come with microgrids, we’ve condensed it down to the top three reasons they rock. 1. COST Installing an energy storage solution and microgrid along with PV panels allows a solar system to store energy during peak sunlight hours and ration it for when power companies increase the time of use rates for electricity. Not paying a premium for electricity can save homeowners up to $1000 a year or more.  The development of better and more affordable batteries, coupled with lower-priced solar systems and government subsidies, makes the homeowner’s cost of going solar competitive with paying for energy generated by a coal or nuclear power plant at a centralized location.  Because solar microgrids allow people to work as a decentralized network, producing power close to its point of use, they cut down on the need for long-distance infrastructure. Reducing the need to build new transmission towers, power poles, transformers, and power lines will allow utility companies to improve the infrastructure they already have. On a macro scale, the cost of utility-scale solar has dropped to around $36 per megawatt-hour, which is cheaper than the MWh cost of building new power plants and equivalent with the cost of running existing ones.  2. AGILE ENERGY SOLUTION TO CALIFORNIA’S BLACKOUTS AND FIRES Recently PG&E chief executive, Bill Johnson, said it could take a decade for the company to improve its electrical system enough to reduce the number of customer blackouts. California’s Energy Commission can read the writing on the wall and has invested over $100 million in microgrid projects.  Solar microgrids provide homeowners with enough backup power generated from the sun to continue with their lives as usual in the ever more frequent instances when energy suppliers such as PG&E and SCE need to shut down.  The change would be beneficial for utility companies, too. Currently, in California, such companies are caught between a rock and a hard place. If a high wind is forecasted, companies are incentivized to be overly cautious and shut off power to millions of people so that downed lines won’t cause another wildfire. But leaving paying customers in the dark is not a viable long-term solution. Smaller microgrids can be...

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Should You Go Off Grid?
Oct22

Should You Go Off Grid?

Let’s face it, most of us have no choice where we get our electricity from. The local electric company is your only option and when a company has no competition, they have no incentive to make you like them.  So customers often look at solar panels and get to thinking… can I go off the grid? Typically, off grid systems are only installed on homes built where the grid isn’t available. It is not uncommon for an electric company to quote $100,000 or more to bring power to a rural property that is being newly developed. So they want you to pay $100,000 to bring in the lines so that you can pay them ever month for electricity when $100,000 will buy you an absolutely amazing off-grid solar power system. If this is your situation, you should definitely go off grid.  But if you currently own a house that is connected to the grid, the answer is not that clear. Yes, we know you don’t like the electric company and nothing would make you happier than to divorce yourself from them permanently but let’s look at the options before jumping into that decision. First, the cost of a solar power system increases dramatically when it changes from grid-tie to off grid. In order to be completely independent from the electric company, you need to have a system that generates the maximum amount of power you may need even in during those months when the days are short and the sun is low in the sky. You also need batteries to store the solar energy produced during the day so you have power to get through the night. Even more batteries if you want to have enough stored energy to get through a rainy day when the solar is producing little to no power.  Also, you shouldn’t have solar be your only power source. People who live off the grid usually have a diesel or natural gas generator as backup. This is necessary because the amount of batteries needed to run a house through a whole week of cloudy/rainy weather would be ridiculously expensive and take a up too much space. The generator may also be needed to cover your needs when a piece of equipment like an inverter or charge controller needs to be serviced. So you have to add the cost of a generator to your already too expensive solar power system to comfortably disconnect yourself from the electric company. Example of a gas generator When you stay connected to the electric company, you can put the solar panels on the roof without needing the batteries. You can...

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Sizing Your Solar Power System
Oct10

Sizing Your Solar Power System

You know you want to install solar, but how much solar do you want to install? There are many factors to consider when making decisions about system size. The system size will be dependent on how much energy you want to generate. If you are doing a grid-tied system, you will start by looking at your electric bills. You should add up the last 12 months of electric bills so you have your annual usage. If you only use one month or one season, you can end up way off because your electric needs can change dramatically from summer to winter.  Sample Electric Bill – look for the kWh! Once you know your annual usage, you should ask yourself some questions. If you have solar on your roof and you’re no longer paying crazy high prices for every kilowatt hour (kwh), what might you do differently? Would you turn the air conditioning setting down a couple of degrees so you never break a sweat? Would you buy an electric car? Do you have any other plans like installing a swimming pool? If you answered yes, then you will want to add some kwh to your current usage to account for the additional air conditioning run time, the electric car, the swimming pool or whatever else you might dream up that will use extra electricity.  The next big question is how much of this projected energy usage do you want the solar to offset. This will depend on your electric rates and how your electric provider deals with net metering. If your local utility company gives you full retail credit for every kwh that you feed into their system then you should consider a system that generates close to 100% of your projected usage. Going over 100% is generally not beneficial as most utilities will not pay much for the excess power generated over the course of a year.  Sample electric bill before and after solar If you are sizing an off-grid system, you will have to do a little more work to get your projected usage.  You will need to make a list of everything that will use electricity. Then you have to determine how many watts each of those items will use and how many hours you plan to run them. You can multiply the watts by the hours to get watt hours. Divide the watt hours by 1,000 and that will give you the kilowatt hours (kwh). Now you know what you need to generate but that still doesn’t exactly tell you what size system to install.  Because there are so many factors (like location, weather and...

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How Solar Works
Oct09

How Solar Works

If you look at the roofs around you, you will see that more and more people are installing solar but what is it all about and how does it work? The point of installing solar is to save money, but that is the end result and we should start this story at the beginning.  The solar panels are officially called photovoltaic modules. Photovoltaic is really hard to say, so most people call them PV modules or just go with the commonly accepted and less technical name “solar panels”. The solar panels should be installed at a good angle to the sun which is generally going to be south. East or west also works with west having an advantage of producing more energy in the afternoons which is desirable if you are on a Time-of-Use electric rate (you can see our other articles for more details on that). Most people install the solar panels on the roof but if you have the space, you can install them on a ground-mount rack.  Roof vs ground mounted solar When the sun hits the solar panels, they produce DC electricity. When you buy the solar panels, you will also want to get an inverter (or microinverters) to convert the DC power to AC power. In a Grid-tied system (which is the kind you want for your house unless you are not hooked up to the electric company), that inverter (or microinverters) will be connected to the main service panel of your house.  The power from the solar will flow to all the lights and appliances in the house and any excess power that you don’t use will flow out to the grid, spinning your meter backwards. Your electric company will give you credits for that energy that you give them and apply those credits to the energy that you use at night when the solar isn’t producing.  The amount of credit that you get for the energy you feed into the grid depends on your utility company. In some places customers get full credit, so for every kilowatt hour (kwh) you feed in, you get a kwh back later. In other places, you get less than full credit, but it is still a worthwhile amount. In the end, no matter where you are, every solar panel will lower your electric bill a little bit more which is why solar is a great investment. But, there is a limit to the savings. You can only save the amount of your electric bill. Except for very unusual circumstances, you will not be paid more than a few pennies, if anything, for excess energy generated over...

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