Solar Planning Steps
Are you ready to explore the idea of solar but feel like there's just too much to figure out? You're not alone. Solar systems have a lot of moving parts: panels, inverters, batteries, and even some calculations, but it doesn't have to be overwhelming.
I'll walk you through the basics of how to figure out your energy needs, use tools to size your system, and even tackle a few technical details like cold temperature calculations.
If it still feels like a lot, stick around until the end because I'll share the biggest trick in the book to make your solar Journey a whole lot easier.
Understanding Your Energy Usage
The first step in designing your solar system is understanding your energy needs and goals. Start by checking your utility bills for the past 12 months. Look at the total kilowatt hours you've used each month and calculate your average.
This gives you a baseline for the energy your solar system needs to produce. For example, if you use about 1,000 kilowatt hours a month that's your starting point for a system size.
That’s why we start and design exercise by asking for your utility bill, or at least your monthly usage.
Of course, it’s always advantageous and advised to see if you can reduce your energy use by becoming more efficient, but that requires doing a specialized energy audit, looking at changing appliances etc., and let’s be honest, a lot of people just can’t be bothered even to think about it. More power to you if that’s what you want to do.
Next, think about what you want your solar system to do. Are you looking to fully offset your energy usage, reduce your energy bill, or start
small and expand later.
If you're starting smaller, it's important to plan for a subpanel. A subpanel allows your system to prioritize powering essential loads. Ensuring your solar setup works effectively without needing to handle your entire home's energy needs. Your goals will determine the right type of system.
If you're staying connected to the grid and focused on saving money, a
grid tied system is a great option.
For complete energy Independence and isolated loads, an off-grid system might work best.
A hybrid system balances both using solar during the day and battery power at night. If backup power is your priority, decide whether you need enough energy for essentials like your fridge, lights, and medical devices or back up for your entire home.
It's also important to consider power outages. A small battery bank might cover a single day but several days of autonomy will require more battery storage (at a greater expense).
Location, Location, Location
It’s not just real estate, location matters too when it comes to solar.
Using tools like PV Watts (https://pvwatts.nrel.gov/), you can estimate how much sunlight your area gets. For example in Texas you might see about 5.5 Peak Sun hours a day, which adds up to 165 Peak Sun hours a month. A bit higher than what you'd find in places like the Northwest.
Peak Sun hours are a key piece to understanding how much sunlight your panels will have to work with each day.
However, to estimate how much energy your system will generate over time, you'll also need to know your area's production ratio. The production ratio builds on Peak Sun hours by accounting for seasonal variations in weather and efficiency losses.
For example, in a location with 5.5 Peak Sun hours per day, the production ratio might be around 1.5, meaning that for every kilowatt of installed solar capacity, the system will produce about 1,500 kw/hours annually. Areas with consistent sunlight like the Southwest tend to have higher production ratios while areas with more seasonal variations like the Northwest have lower ratios. Understanding both Peak Sun hours
and the production ratio helps you better estimate how much energy your system will generate and how many panels you'll need to meet your goals.
How Much Are You Willing to Spend?
Finally, don't forget your budget. Solar systems can scale with what you're ready to invest. Start small with a few panels and an inverter, or go all in right away. Solar is flexible and there are often local or governmental incentives to reduce cost. For the latest policies and
incentives in your area you can visit https://www.dsireusa.org/ for up to to date information.
By defining your goals and understanding your energy needs you'll
have a solid foundation for building your system.
Sizing the Solar System
Now let's look at sizing the three main components of your solar
system: panels, inverters, and batteries. Each plays a key role, and it's important to make sure they all work together and meet your energy needs.
Estimating Panels
Panels are the foundation of your system and determine how much energy you can produce. To estimate how many panels you'll need, start with your daily energy usage.
If you use about 1,000 kilowatt hours a month divide that by 30 to get roughly 33 kilowatt hours per day. Next consider your area's production ratio, which adjusts for local sunlight conditions. For example, in Texas the ratio is about 1.5. Dividing your daily energy usage by this ratio gives you a sense of how much power your system needs to generate each day. Using 400 watt panels, you can divide your energy needs by the panel wattage to estimate the number of panels required, but remember panels lose some efficiency due to factors like dirt and shading.
It's a good idea to oversize your system slightly around 15 to 20% to account for these losses. Finally consider your property layout. Do you have enough roof or ground space for the panels? If space on the roof is limited or there is no good orientation, ground mounted systems can provide a great alternative. Don’t have space for a ground mount? Then how about a solar carport or a solar pergola.
Placing the Panels
There is both a science and art to placing panels. On the roof, for example, is it flat or is it at some sort of an angle. And which way is it facing? You generally want them facing south but a certain amount of east and west is acceptable, while north facing is the worst option and generally.
Of course, the optimal angle with also vary over the course of the year. Are you going to have a fixed angle or some mechanism to have it be adjustable. With a flat roof, with your panels lie flat or will you use a tilt system, and will that system be adjustable.
What sort of surface is the roof made of? While there are all kinds of racking systems for various roof materials, it is important to choose the one that best matches your roof. Are you going to have roof penetrations or can you use an adhesive system with no penetrations? Will the system be ballasted with no roof penetrations? Can the roof support the weight of having a ballasted system?
There are many software systems that will help with placing the panels. There are too many to go through here so here's a list of just a couple to give you an idea: OpenSolar (https://www.opensolar.com/), GoSolo (https://gosolo.io/), Aurora (https://aurorasolar.com/), and many more.
The Effect of Cold Temperatures
Here's an important detail you don't want to overlook: cold
temperatures can increase your solar panel voltage. As temperatures drop below 25° Celsius or 77 degrees Fahrenheit, which are standard test conditions, the panel's voltage rises because of its negative temperature coefficient. While there's a formula to calculate this, here's an easier way to think about it. The voltage increases by about. 3 to 4% for every degree celsius below 25° C. For example, if the lowest temperature in your area is -10° C, that's a difference of 35 degrees. Multiply that by the panel's temperature coefficient say 33% and you get an 11.55% increase. A panel with a standard voltage of 40 volts would rise to about 44.6 volts under those conditions. This voltage increase adds up quickly when panels are wired in series, so it's critical to make sure your inverters and charge controllers can handle the higher voltage safely.
Inverters
Your inverter is a key part of your solar system. It's what converts the energy your panels produce into usable electricity for your home. Choosing the right inverter means thinking about your energy needs and the type of system you're building.
For example, an inverter can either use DC power directly from the panels, or you can get local optimizers which directly output AC power.
Peak Power
Whether it's grid tied, off-grid, or hybrid, you'll also need to ensure your inverter can handle your home's Peak power demand, the highest amount of power your appliances might draw at one time. Start by listing the wattage of appliances you might use simultaneously. Add those together to get your Peak demand. Choose an inverter or a combination of inverters with enough capacity to handle that load and don't forget to check its surge capacity for short-term power spikes.
Some appliances like refrigerators have a motor which requires a large inrush current whenever the pump starts up. These types of applications can require some sort of a “soft start” mechanism to reduce the current spike which might otherwise exceed the system or trip a breaker. Or a microwave can consume large amounts of power for a brief duration. These generally are known as the duty cycle.
For example, imagine you're running several appliances at once: a water heater that uses 4,500 Watts, three Mini Splits pulling 3,000 Watts, lights using another 700 Watts, refrigerator at 800 watts, and cooking appliances drawing 2,500 Watts. Altogether that's a peak demand of 9,500 Watts for this setup. You would need an inverter or a combination of inverters that can handle at least 10 Kw. You could choose a single 10 kilowatt inverter or go with two 6 Kw inverters to meet this demand. Or you could think about ways to make your home more energy efficient, as discussed earlier.
Now think about how you want your inverter to function in your system. Does it need to handle all the power for your home, or is it just supplementing certain loads. If you're using batteries, will it also manage charging and discharging. These are important considerations when selecting the right inverter for your setup.
Lastly, your inverter needs to be sized correctly for your solar array. It should handle the energy your panels generate now, but also be flexible enough to grow with your system. If you're planning for future
expansion, choosing the right inverter up front will ensure your system works efficiently today and can adapt to meet your goals down the road.
Stationary Storage: Batteries
Batteries store energy for when the sun isn't shining. When sizing your battery bank, it's important to think about nighttime usage. Since your solar array should recharge the batteries during the day by focusing
on covering your overnight needs you can design a more cost effective system without having to size for a full 24-hours of autonomy.
This is frequently called the “self-consumption” model, which is particularly advantageous in states that have Time of Use rates when they charge more for electricity in the evening when consumption is at its highest on the grid. This is commonly referred to as the “duck curve.”
By using your batteries during peak usage times, you avoid buying from the grid when it is most expensing, and you can recharge the batteries during the day when the sun is plentiful while also powering your home, or late at night when rates are cheaper.
In some jurisdictions, this is referred to as Net Energy Metering (NEM) and there are various regimes in place, typically numbered, like NEM 1.0, 2.0, or 3.0.
Calculate Battery Requirement
To calculate your battery needs, estimate how much energy you'll use at night and multiply that by the number of backup days you want. For example, if your nightly usage is 15 kilowatt hours and you want two days of autonomy, you'd need 30 kilowatt hours of storage. To further complicate things, batteries also come in various voltages, with 12V, 24V, or 48V nominal. So the inverter has to be matched to the battery voltage. There are even some DIY batteries that use old scooter or other EV batteries at 36V.
Most lithium server rack batteries provide around 5 kilowatt hours each or increments there of (10, 15, 20 etc), so in this case you'd need six batteries. To get around the very heavy weight of larger batteries, many manufacturers have implemented “stackable” designs.
To reduce the strain on your batteries consider managing heavy loads during the day when your array is producing energy. This approach can help optimize your system and lower the number of batteries required. If you're trying to estimate your system size, there are some great online calculators to help. However these tools only provide pieces of the puzzle and won't give you the full picture.
The PV Watts calculator from the national renewable energy laboratory is an excellent starting point. It estimates your systems annual energy production based on your location and solar radiation levels. To use it, you'll enter details such as your location, array size, and panel type to get a general idea of your system's output. For greater accuracy the tool also requires information like panel tilt and degree of south orientation and shading details you might not have finalized yet.
Another useful tool is the solar panel string sizer from eg4 Electronics which you can find on their website at eg4electronics.com (https://eg4electronics.com/wp-content/themes/hello-elementor/eg4-solar-panel-string-sizer/) under the resources tab. It's especially handy if you're using eg4 inverters, Mini Splits, or charge controllers.
This tool helps you see how different panel configurations will work with your system, but to use it effectively you'll need to know the minimum and maximum temperatures in your area and the impact safe voltage ranges.
If you're unsure about local temperature extremes, try searching for the highest and lowest temperatures in your area over the past 10 years. The University of Florida's solar reference map (https://energyresearch.ucf.edu/solar-certification/solar-reference-map) is an excellent source for this.
These tools are helpful, but they're just pieces of the puzzle. Designing a complete solar system involves putting off all of this information together to make sure your components work together seamlessly.
Summary and Conclusions
If you've made it this far congratulations. You now have a solid foundation to start planning your solar system. As you can see, there’s a lot to it, and we’ve just barely scratched the surface in this already admittedly long introduction and overview.
You've assessed your energy needs, explored your system goals, and even learned some technical calculations, but here's the truth: solar design can still feel overwhelming and that's okay. Now remember when I said earlier that I'd share the biggest trick in the book? Well here it is. You don't have to do it alone.
There are plenty of people who can walk you through all the different options and come up with a system design that meets your needs.
Just to throw it out there, I’ve got tons more information on my web site: www.solartechnicalservices.com and I can be reached at peterk@solartechnicalservices.com. Or you can call me at +1 (415) 6 0 1 - 6 3 3 2. I love geeking out on this stuff.
If you're starting from scratch they'll create a detailed custom quote with everything you need: panels, inverters, batteries, and all the components required to build a system that meets your energy goals and budget.
First off, we’ll map your roof and identify the best panel placement. We can also calculate shading and optimize your system's performance to meet local requirements whether you're planning a grid tied system, a whole home backup, or an off-grid setup.
For customers needing a permitting packet specific to their location we can design a solution tailored to your goals, budget, and unique needs, and the best part is people like me can be with you every step of the way whether you're starting small or going All in.
Or if you just need design and want to get your own permits and DIY it.
If you've already done your research and have a good idea of what you want, that's great too and we can be the expert second set of eyes to check your work ensuring all your components are compatible and designed for maximum efficiency. We can help fine-tune your setup to make sure it works seamlessly while staying as cost efficient as possible.
I’m not just here to sell you products. My mission is to change solar in favor of the homeowner. To take control of your energy future, get out from underneath the thumb of the utility companies, go from feeling overwhelmed to feeling confident in your solar Journey.
Solar is a big step, but you don't have to take it alone with the right tools, knowledge, and support we can design a system that works perfectly for you and I’m here to help.