To answer your question “how to calculate my solar power needs” you have to first find out how much energy you require, and from there you can figure out the rest. For that you will need you must consider the following factors first:
1. Check Your Monthly Power Bill To Fix Your Solar Energy Goals
Your power bills will give you a base to target your solar energy production goals.
For example, if your monthly bill is $150 i.e. $1800 for the whole year, then it is more than likely that you will not need a solar system that will produce $2000 worth of energy.
It is better to check what rate you have been paying for last five to ten years because often it has been found the bill payer gets charged more than he used to pay five years back, even though he’s using about the same amount of energy.
As your solar panels will produce consistent power for at least 20 years you will not face such kind of inflation. This is why your savings from solar installation will increase as time passes, even if your energy usage doesn’t change.
2. Determine Your Monthly Power Usage
To find your monthly power usage first check your power bill – it will be listed in kWh or Kilowatt-hours.
Next, sit and think about possible circumstances that may increase (or decrease) your power usage in future.
For example – Do you wish to have a hot tub in future? Planning a second fridge?
How about an electric car?
These type of additions will significantly add kWh to your monthly power usage. So if you know that there are some electrical appliances or equipment that are planned to be added to your household in near future, factor those into your household energy requirement.
From the first two factors discussed above, you can now…
3. Fix Your Solar Power Production goal
Now that you have a fair idea about your monthly energy cost and power usage, it is time to decide how much of your total energy requirement do you want to produce from solar? Would you like to produce 80% of your total energy requirement from solar? 50%? All of it?
It is important to decide this because it will determine how many solar panels you will actually need. To do this calculation knowing your kWh usage is mandatory. So If your average monthly usage is 1500 kWh, and you want to produce 70% of that from solar panels, you’ll need to install a system that will generate 1050 kWh per month.
Now that you know your goal, let’s move on to the other factors that you need to consider.
4. Factor in the Inconsistent Solar Power Production for Summer and Winter
The amount of sunlight you will get is not consistent year-round anywhere in the US.
So, what will happen if your solar system produces extra energy in the summer months? What will you do with this excess energy?
Would you like to store the extra energy in solar battery for storage?
If you don’t want to store it or can’t sell it back to the grid because your utility doesn’t allow it, then producing excess energy than you actually need is of no good.
This is the reason why most people set a solar power production goal of less than 100%. If your goal is to produce 70% of your energy needs from solar, then you are not going to generate more than you need, even in the summer.
Just be aware that your solar panels will not produce same amounts of energy throughout the year. It will vary depending on the season.
Now that you are aware of this factor, reconsider your solar power production goal decided in last step, with excess energy possibility in mind.
5. Calculate your daily Power usage i.e kWh per day
This is easy. Just check your monthly power usage from your bill and divide it by 30. So if you are using 1500 kWh per month your daily requirement is 50 kWh.
This figure will help you to find out how many solar panels you will need to install.
6. Calculate the solar system size you will need
And now to the final step. Considering that your location gets 5.5 hrs of direct sunlight a day here’s how you decide your solar panel size:
Divide your monthly kWh power consumption by average direct sunlight you get and multiply it by 30 days.
To illustrate, consider that your monthly kWh consumption is 1500 kWh.
So to produce 1500 kWh your will need ( 1500/ 5.5 * 30) = 9.09 kWh solar system.
A 9 kWh solar system means that the system will produce 9 kWh of solar power every hour of direct sunlight. So a place that gets 5.5 hours of direct sunlight will make 5.5 *9 = 49.5 kWh per day
So going by the example before, if your daily power requirement is 50 kWh per day (remember factor 5 above) you can have a fair idea to determine how many solar panels you will need.
Now equipped with all this information you can inform and get a quote from the solar installers.