Work Through this 6-Step Process and Learn Your Ideal Solar System Size
For hog farmers looking to save money, one of your prime targets should be your utility bill. You may have considered installing solar panels to defray your energy costs, which average about $40,000 per year for a typical wean-to-finish site.
But the question is, how many solar panels should you install?
The number of panels determines your total installation cost more than any other variable. So having an estimate for how many panels you want should be one of your first goals.
An agricultural solar consultant can give you this information and much more. If you’re already fairly committed to solar power for your hog farm there’s little reason to work through the 6-step process below all by yourself. Request an Ag Solar consultant to visit your farm, share some system size options and quotes, and answer your questions.
However, if you want to do a little more investigation on your own, working through this 6-step process will teach you more about solar and give you answers to some of your main questions.
How Many Solar Panels Do I Need? Get Answers in 6 Steps
Step 1: Add Up Your Current Energy Costs
Dig out your last 12 months of power bills and add up the costs. You want an annual total, as well as an average monthly total.
This will allow you to choose a target amount for how much of your power bill you want your solar panels to wipe out. If you average about $40,000 per year in energy costs, that’s about $3300 per month. When you reach the end of this process, you’ll have a rough sense of what portion of that you can eliminate with solar.
You might also want to dig out power bills from, say, five or ten years ago if you have them. Take note of how much more you’re paying for energy now than a few years ago. This is due to inflation. With solar panels powering your hog farm, you will be escaping from energy inflation. In other words, your savings increase as time goes on, because without solar, you’ll be paying more in ten years for using the exact same amount of power as today.
Step 2: Add Up Your Energy Usage in kWh
Using the same bills from the last 12 months, add up your monthly kilowatt-hours for the year. Again, you want both an annual total, and an average monthly total.
Also, take note of which months tend to use the most energy, and which use the least. Do you use more power in the summer or winter? Depends on if you use more energy to cool your wean-to-finish site in the summer, or to heat it in the winter. But temperate control also depends on the stage of growth of your hogs.
Either way, you’re spending a lot of energy on heat lamps, lights, and fans. You want to know how this breaks down month to month, and season by season.
Why is this important?
Because your power usage may hold pretty steady for the next ten years, but the costs will keep going up. Solar panels will cancel out usage, not cost. If you’re using 5000 kWh per month and your solar panels produce 4500, then you only have to pay for 500. In that scenario, you have avoided 90% of the effects of inflation.
Step 3: Decide How Much Power You Want From Your Solar Panels
You can go for 100% production if you want. But this is not so simple a decision. Here’s why:
Suppose in August you use about 4000 kWh, but in December you use 6000 kWh.
If your solar panels produce 4500 kWh in the spring and summer months, what happens to that extra 500 kWh of production? Your panels will be over-producing, generating more than 100% of your needs. But when December hits, and it’s cloudy and rainy (depending on where you live of course), your panels might only produce 3500 kWh.
The point is, it’s impossible to get 100% solar production year round. Weather patterns and your power usage changes. So what can you do?
First, find out if your utility, city, or state government has a net metering or solar buyback program.
If so, this is good news. This means, if your solar system produces excess power, you can sell your excess back to the utility and get credit on your bill. In our above scenario, you’d get a credit for the extra 500 kWh produced in August, and perhaps more in September. Let’s say in October, you now start using more power than your solar produces. Your credits would now apply to your bill until they get used up. By December, you might then have to pay a small power bill.
See how that works? With net metering, you get the benefit from all your solar production. So in that case, you can shoot for a higher production goal. Maybe, for instance, go for 100% of your usage in your summer months. An agricultural solar consultant can help you work through those details and options.
(And the full truth here is that this excess power issue happens every day, not monthly, because the sun comes up every day. One day you might produce excess; the next you won’t).
On the other hand, if you do not have access to net metering, you will most likely want a solar array that produces less than 100% of your power in all 12 months of the year. Most people go for a goal of 70-80%.
This lowers your installation costs, and assures you that you’ll never over-produce and get no value for the excess power production.
The one exception here is, if you want to spend extra money on solar batteries, then you can do pretty much whatever you want, because your batteries will store any extra energy production. That does add to the initial cost, but you can pretty much zero out your power bill with this approach.
So – take all this information, and set a power production goal.
Step 4: Determine Your Average Daily Direct Sunlight
You’ll need to look this one up for your area. And to be clear – your ‘area’ doesn’t just mean your state or city. You can get general figures for that pretty easily online. And if you’re trying to go through these six steps fairly quickly, that’s fine for now. Just search for “average daily direct sunlight in” your state or city.
But if you want the most accurate sunlight information, you’ll want measurements for your specific hog farm’s location.
Why? Because the tilt of your roof, which way your roof faces, nearby obstructions such as trees or tall buildings – these and other factors affect how much direct sunlight your roof receives.
The best place to find this level of information is the PV Watts calculator.
But be warned: This tool is not for the casual solar inquirer. This is for people who love details and precision. Again, if you request an agricultural solar consultant to come visit your farm, you’ll get most of the same information from them. But if you want to find this out for yourself (and learn a lot along the way!), use the calculator yourself.
For help, here’s an article, with several screenshots, that walks you through how to use the PV Watts calculator.
You’ll get far more information from PV Watts than just your average direct sunlight. For one, it gives a per-month average, not just an annual one. With the other numbers you’ll plug in, you’ll also learn how much AC energy your chosen number of solar panels will produce each month, and the dollar value of that energy.
For our purposes in the next step, you’ll want a daily average for direct sunlight.
Step 5: Calculate Your Solar System Size
You’re almost there! You’ll know how many solar panels your hog farm can use in just two more steps.
For this step, you’ll need two numbers from previous steps:
Your average kWh you want to produce per month (from step 2)
Your hog farm’s average direct sunlight hours per day (from step 4)
The math looks like this:
kWh per month / (avg sunlight per day * 30) = kW solar system
For example, suppose you want to produce 3000 kWh per month on average and your farm gets 5 hours of sunlight per day.
That would be 3000/(5 x 30), which is 3000 divided by 150, which equals 20.
So this particular hog farm would be looking for about a 20kW solar energy system.
If you wanted to produce 2500 kWh, or 3500, just change that first number in the calculation. This is where step 3 comes in. That step is where you decided how much power you want to produce, the percentage of your bill you want to replace with solar power.
If you use 3000 kWh per month but want to produce 75% of your power from solar, you would want a system that produces 2250 kWh per month. 2250 divided 150 equals a 15 kW solar system.
Then you’re ready to see how many panels that is.
Step 6: Calculate How Many Solar Panels You Need
Put simply, you just take your solar system size (what you just calculated in step 5), multiply it by 1000, and divide by the wattage of your chosen model of solar panels. Here’s the math equation:
Solar system size x 1000 / panel wattage = # of solar panels
You can get solar panels that produce anywhere from 45 watts up to nearly 400 watts. Obviously, the 400-Watt panels cost more. But you will need fewer of them to meet your production goal.
So, let’s say the 20 kW solar array from our step 5 example decides to go with solar panels that produce 315 watts each. This is a fairly common figure.
20 times 1000 equals 20,000. Divide that by 315, and you get 64 panels (you have to round up if you want to hit your goal).
This particular farmer would need about 64 panels to produce 3000 kWh per month.
(By the way, we multiply by 1000 because there are 1000 Watts in a kilowatt).
If you want panels that produce less power, like 200-W panels, you’ll just need more of them. If you want premium panels up around the 370-W range, you’ll pay more for each but you’ll need fewer of them. Just use the math above and play with the numbers.
Again – this approach only gives you approximations. If you use the PV Watts calculator, your answer will be more accurate. But it’s still an estimate because every location has specific variables that can only be measured on site.
But hopefully this was helpful and now you have a clearer picture of what it would take for your hog farm to go solar.
If you want personalized solar estimates for your specific hog farm, ask an agricultural solar specialist to visit your farm, get your solar measurements, and give you a free customized quote.