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How Many Solar Panels Do I Need to Charge my EV?
Aug03

How Many Solar Panels Do I Need to Charge my EV?

We are still miles away from being able to produce a practical, self-contained solar powered car but that does not mean you have to give up your dream of driving on sunshine. If you have an electric vehicle, you are halfway there. All you would need to add is some solar panels to your home charging station. Before we get into system sizing, many people have the idea that the solar electric vehicle charging station must be a stand-alone system, but that is not the best configuration. If the solar panels are only connected to the EV charger and you don’t drive anywhere that day, the solar power is wasted. The way to avoid that is to install a standard grid-tied system or a system with a SolarEdge grid-tied inverter with an integrated EV charger. With either of these options, the solar power produced when you don’t need to charge your car will be used to run other loads in your house or backfeed to the grid so it would never be wasted. So how many solar panels do you need to charge your EV? That depends on how much you drive. The average EV uses about .3 kwh per mile. This means if you average 50 miles per day, you would use about 15 kwh per day to keep it charged. With solar, it always best to talk about annual production because solar panels will always produce more energy in the long summer days than they will during the winter months. So let’s look at the annual usage for the car which is just the daily number multiplied by 365 days. In our example above, 15 kwh multiplied by 365 days is 5,475 kwh. That is the amount your solar would need to generate to off set the electricity used by the car annually. We have discussed system sizing in previous articles, but to give a short summary, you can start with PV Watts at https://pvwatts.nrel.gov/. Follow the prompts which start with entering your zip code so your production numbers will be location specific. It will also ask for a system size in kilowatts (kw). A good starting point is to take that kwh number you want to reach and divide it by 1,500. In our example above where you wanted to generate 5,475 kwh it would be 5,475/1,500 = 3.65 kw. Once you see the output on that system size, you can adjust the size up or down to get to the goal. You will also need to enter the tilt and Azimuth of the system. Tilt is just the angle from horizontal. If the system will...

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How Many Solar Panels Do I Need?
Jul25

How Many Solar Panels Do I Need?

Once you have chosen to go solar, the very important question arises. How many solar panels do I need? The first part of this is to figure out how many Watts of solar you need. This will depend on how much energy you want to generate. If you are shopping for a grid-tied system, you will find the answer in your electric bills. Every month, the electric company has tallied exactly how much energy (kiloWatt hours or kWh) you used so they could bill you for it. The meaning of that kWh figure and kW is commonly confused. The kWh is merely kW over time. For example: if 10 kW is consumed for 2 hours, that is 20 kWh. An analogy is kW is like a speedometer, indicating how much power is being consumed at one point in time. And kWh is like an odometer, indicating how much power has been consumed over time. All you have to do is look at the history of kWh usage on your paper electric bills or your online account with the power company. We recommend reviewing at least 12 months of electric history. You will definitely notice a difference in usage from winter to summer and basing your needs on just one month’s bill can be a big...

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What California’s New Solar Mandate Means for Home Builders
Jul20

What California’s New Solar Mandate Means for Home Builders

The future of solar in the golden state is shining much brighter now that that the California Energy Commission unanimously voted to require that all new homes built after Jan 1,  2020 have solar panels. Updates to the Title 24 Standards decree that builders who obtain construction permits issued after the mandate goes into effect must fit new houses with a solar array that has an annual electrical output equal to, or greater than, the dwellings annual electrical usage. If you’re a home builder in California, here’s three reasons this change will be advantageous for you:   LOWER MONTHLY HOME PAYMENTS In a market where home prices are already high, the requirements are estimated to add nearly $9,500 to construction costs or an additional $40 a month in mortgage payments. So how does that save the eager home buyer money, you might wonder? According Energy Commission spokeswoman Amber Beck, increased home energy efficiency will shave on average about $80 off monthly bills. Subtract that from the increased mortgage and you have a net gain of $40. Even better is the fact that it’s a pretty sure bet electrical rates will continue to rise over the next few years, and suddenly it becomes much more appealing to own a new energy efficient home fitted with solar than an older one that costs more money to power.     LOCATION IS EVERYTHING! Much like selling a house, location is everything when it comes to decking out a house with a solar array. The location of a home will determine how many panels it needs to satisfy the Title 24 Standards, and will make building in areas that have a higher Sun Number more appealing. For reference, California’s average system size accross its different climates comes to around 3.38 KW, or about twelve 3ft x 5ft solar panels. Location will also come into play when it comes to knowing where to source bulk deals on equipment to maximize profits. Wholesale online dealers such as GoGreenSolar will usually go the extra mile and help with contracting out the installation and offering advice on the best direction and angle to build a roof.   UPSELL The new building standards are also offering a credit for solar capacity combined with on-site energy storage. The credit is meant to encourage builders and/or buyers to include energy storage systems to increase the efficiency of their solar array and can be offset with monthly payments. Ultimately, while the code is might appear ambitious at first read, it leaves a lot of interpretation and wiggle room up to the builders to determine how they will implement it. If necessity...

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60 Cell Vs 72 Cell Modules
Jul16

60 Cell Vs 72 Cell Modules

When shopping for PV modules, you must choose between 60 cell and 72 cell modules. The extra cells mean extra wattage and while many people make the assumption that more is better, this isn’t always the case. There are two basic ways that the extra cells will make the solar panels different, voltage and physical size. Both of these factors should be considered when making the choice. Because all the solar cells in a PV module are connected in series, the 72 cell module will be about 6 volts higher than a 60 cell module. If you are using them with a string inverter this means less panels on each string. If you are using them with microinverters or DC optimizers, you will have to make sure the equipment you choose is designed to handle the higher voltage. Microinverters and DC optimizers for 72 cell modules will typically have a maximum input of 60 volts to prevent issues in even the coldest of temperatures. So now let’s talk about size, which definitely does matter. All standard solar cells are similar in size and efficiency, so the 72 cell PV module is going to be a bit larger. You may be getting more wattage, but your wattage per square foot is still the same. The typical solar module is 6 solar cells wide, so a 72 cell module is the same width as a 60 cell module, but it is about a foot longer and 8 pounds heavier. The typical size for a 60 cell module is 66” x 40” and weighs in at 40 pounds while the 72 cell module is going to be about 78” x 40” and 48 pounds. It doesn’t sound like much of a difference, until you are the one that has to move it around. Carrying a standard 60 cell module on a steep sloped roof is awkward, but the 72 cell module, which is likely taller than your biggest crew member, can be a real bear. If it is a two story house, lugging it up to that roof is not going to be fun either. Another challenge of the size is trying to maximize the wattage that you can fit on a residential roof. With limited roof space, the flexibility of the smaller 60 cell module can be a great advantage. Especially as more states are adopting stricter codes for fire access, using a shorter module often means being able to install a whole second or third row which will result in a larger overall system size. Transport also needs to be considered. Trucking companies already don’t like our non-standard sized pallets...

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You Can Add Energy Storage to Grid-Tie Solar
Jul11

You Can Add Energy Storage to Grid-Tie Solar

Energy storage systems for solar are becoming more popular. People want to have back-up power during power outages and changes in net metering and time of use electric rates can give energy storage options a better payback. When going solar, many people feel pressured that they must make the decision about energy storage up front. But the truth is that adding energy storage to an existing grid-tied system is easy. The best part is that you do not have to remove or change any of your existing grid-tie system when you add batteries. This surprises many people who understand traditional solar power systems with batteries, but it is all about DC coupling versus AC coupling. For many years, solar with energy storage was always set up as a DC coupled system. Solar panels were connected to a charge controller which managed the solar power going into the batteries and kept the batteries from being overcharged. The power from the solar panels and the batteries is all DC, hence the term DC coupling. Then a battery-based inverter was used to convert the DC power from the batteries to AC power to feed the loads. This technology is all still used for some systems, but it is no longer the only option. This is great news for anyone who has grid-tied solar already installed and wants to add energy storage. Grid-tied systems have the solar panels connected to an inverter (or microinverters) that change that DC power from the solar to AC power from the loads. These grid-tied inverters do not work with batteries, and until the last decade, installing a battery system meant removing that grid-tied inverter and replacing it with a charge controller and battery-based inverter. But now there is a better way that is rapidly gaining popularity and it is called AC coupling. In an AC coupled system, you connect the AC output of a battery-based inverter to the AC output of a  grid-tied inverter. This will work with any grid-tied inverter or microinverters, but you must be careful in your choice of the battery-based inverter as it needs to have the right functionality. Inverters like the Outback GS Radian are specially designed with AC coupling in mind. Outback even packages it with batteries as a complete kit to make the choice easy. If you have a grid-tied solar system, you probably already know that it does not work during a power outage. The reason for this is that grid-tied inverters will not make AC power unless they have AC power coming to them from the grid. When you install the battery-based inverter, it creates AC power that...

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