Solar Panels: How Many Do You Need?
Tie in Your Appliance Use with Your Solar Panel Requirements
To get an idea about the number of solar panels and batteries you will need to generate solar electricity, you will need to make some calculations with respect to the energy used by the appliances in your home as well as how often they are used.
Assessing Power Usage
You need to know such details as the cubic feet of your refrigerator and calculate the wattage based on the number of people who regularly use it. Televisions should be assessed by how much time your family watches the tube per day. The microwave oven can be assessed on its wattage or power rating. Look at the amount of time the microwave is used during the course of a day.
Evaluating Your Use of Lighting
Of course, lighting is a major determinant. Add the total wattage of all the lights in your home. For example, four lamps with 60 watt bulbs in a single room equals 240 watts. Ask yourself – How many hours per day are the lights left on?
Adding Up the Wattage
The LCD display screen on a computer uses less electricity than a CRT computer screen. So, keep that point in mind while making your calculations. Audio systems and printers will also add to the amount of wattage that is consumed. Any other device in the home needs to be figured in as well. Add the wattage and list the hours of use.
Figuring the Number of Panels
Once you calculate how much wattage the appliances in your home are using, then you will have a better idea of how many solar panels you will need for your solar system configuration. Solar panels for average or small-sized residences usually provide 80 to 100 watts of energy. You will need to know how many batteries will be necessary as well.
Wattage x Usage
Typically, the number of solar panels that you will need is based on a 90-watt panel. The batteries for the system are usually the standard 12-volt kind at 105 amp hours. In order to get a clearer understanding of the solar system size you will require, you need to multiply each appliance’s wattage by the daily usage hours. Wattages for UL listed and approved appliances are generally located near the AC power cord for an appliance.
Calculating Voltage and Amps
In some cases, only amps and voltage are given for an appliance. If so, simply multiply the voltage by the amps and you will obtain the wattage – a formulation that is based on Ohm’s Law. So, if you have an appliance with voltage listed at 120 and amps that are 1.5, you would multiply 120 x 1.5 to come up with the answer of 180 watts.
Energy Usage for Refrigerators
In determining the wattage for appliances, such as refrigerators, keep in mind that they will cycle on and off. So, they really run, in actuality, around one-third of the time. Naturally, the more frequently you open a refrigerator door, the more energy is used as well.
Add all the watt hours for your appliances, then figure your battery needs. Make the assumption that you will need electricity for three days before you need to recharge the batteries. In turn, multiply your daily watt hours by 3.
Determining the Number of Panels
Once you know the wattages and determine the number of batteries you will need, you can easily calculate the number of solar panels to use based on their sizes and wattages.
One Final Note
If you live in an average-sized home (around 1,500 square feet) and pay around $200 each month for electricity, a solar system design of 4 kilowatts may suffice. Of course, the system size, area rebates and where the panels are placed all will determine the size and number of panels utilized.
Watch the video below for more useful tips on solar panels