## Calculators

For off-grid systems you can approximate your solar PV system wattage with this calculator:

##### Recommended Battery Size (24V):

You can approximate your on-grid system wattage with this calculator:

##### Recommended System Size:

You can approximate wire gauge size with this calculator (copper wire only).

##### Gauge Size:
NEC maximum current for different wire sizes
 AWG 16 14 12 10 8 6 4 2 0 Max. Current 10A 15A 20A 30A 55A 75A 95A 130A 170A
Resistance increases with length

The reason different wire lengths bear different ratings is because the electrical resistance builds up as the cable gets longer. At that point, up-sizing the power cable will restore the voltage to its intended level.

Acceptable Power Loss

Undersizing the wire size will result in excessive power (watts) being lost in the wires rather than delivered to the load (battery bank, inverter. Typically we recommend the power loss below 5%.

Voltage Drop

A 5% voltage drop causes an approximate 10% loss in light output. Voltage drop causes a nearly proportional drop in light output. A voltage drop greater than 5% will reduce this necessary voltage difference, and can reduce charge current to the battery by a much greater percentage. Our general recommendation here is to size for a 2-3% voltage drop. If you think that the PV array may be expanded in the future, size the wire for future expansion.

Don't choke the flow of power

On the other hand, installing too large a wire gauge doesn't really have a downside, but there is the potential for better performance. Obviously, there's no need to buy 2-gauge wiring when 10-gauge will do. That kind of overkill would be a waste of money. But if the calculator could lean either way between two sizes, going with the larger wire size would be the smart choice.

## Solar Sizing Calculator

### How to Calculate the Total Watts that Your Electronics Will Consume

The most accurate way to use a solar cost calculator to calculate the total watts (W) that the electronics in your home will consume is to make a list of appliances you have and record their daily watt usage. For example, if you have a television that is 100 watts and you use it three hours per day, that would equal 300 watts per day.

If you’d rather not go around your house to determine each appliance’s wattage and daily usage, you can also reference your monthly electricity bill. Keep in mind that your bill shows your usage in kilowatt-hours (kWh), not watt-hours.

To determine your watt-hours, simply take your kWh and multiply by 1000. If your monthly electricity bill shows that your home used 800 kWh, that would be 800,000 watt-hours for the month or around 27,000 watt-hours per day (27 kilowatt-hours).

### How to Figure Out Your Average Sun Hours Per Day

Various parts of the country receive different amounts of daily sunlight at various times throughout the year. To figure out your location’s average sun hours per day, you’ll want to determine the peak sun hours, not just the times at which the sun rises and sets. Peak sun hours are the times at which an hour of sunlight is equal to at least 1,000 watts per square meter.

You will receive somewhere between three-and-a-half and six peak sun hours in most parts of the United States. The southwest tends to get the most hours, while the northeast and northwest get the least. To get more specific details, you can check an insolation map or use an insolation meter.

Knowing your average peak sun hours is a crucial step in purchasing the appropriate size and number of solar panels for your home’s needs.

### Solar Panel Cost Per Watt

After using the Renogy solar panel calculator to determine the recommended solar panel system, you may want to figure out the solar panel cost per watt for your proposed energy system. Doing so will help you calculate whether using solar power will be worth it for your unique situation.

Solar panels come in a wide range of sizes, from as small as five watts up to 400 watts per panel. The cost per watt has to factor in how many panels you need and at which size. In most states, the solar panel cost per watt ranges between \$2.25 and \$3.25.

### Grid-Tie Solar System Costs

A grid-tie solar system means that your home is connected to the utility company’s grid. With this setup, your main objective might be to cut costs on your monthly electricity bill. Your energy consumption would remain the same as it was previously and the solar energy system would simply complement the setup that your home already had on the grid.

By using the on-grid solar calculator, you can figure out which solar panel kits will make the most sense based on the percentage of solar energy you intend to use. As part of a grid-tie solar system, you’ll also have to decide whether you plan to use your renewable energy as a backup during an outage.

If a primary factor of your solar energy system is to store energy for later use, you will also need to invest in the proper number of batteries. According to the National Renewable Energy Laboratory (NREL), battery-coupled systems can cost about twice as much as standalone systems.

However, there is no additional charge for storing your extra energy, and most states offer rebates and incentives through buyback programs. There are also federal tax credits for installing renewable energy sources, such as solar panels. It’s a good idea to keep all of this in mind when you’re using the on-grid solar calculator.

### Off-Grid Solar System Costs

Using an off-grid solar calculator to determine costs involves a little bit more data entry because your system will also need a charge controller, such as a 3000-watt inverter. These inverters convert the direct current (DC) energy absorbed by your small solar panel kits into alternating current (AC) so that you can use it to power your devices smoothly and safely.

Charger controllers run at either 80% efficiency or 92% efficiency, depending on their type, which the off-grid solar calculator will factor into your result. It’s also important to know how many hours you plan to run your RV or tiny home solar system per day to get an accurate reading from the solar cost calculator.

### Solar Panel Installation Costs

After using the solar panel calculator and purchasing everything you need for your system, it may be possible to install your home solar panel kits on your own. To do so, you’ll not only need to be handy, but you’ll need to have experience with electricity and the ability to safely and securely climb onto your roof.

The majority of people will need to hire professionals, which will add to their solar panel installation costs. In general, solar installers will charge somewhere between \$0.75 and \$1.25 per watt for their labor. This cost is another reason why it’s helpful to use a solar cost calculator to know how many watts you plan to install.

Factoring in the installation costs will also help you to determine your payback period, which is usually around eight years for most systems in the United States.

### How Much Do Solar Panels Cost Overall?

Using a solar cost calculator is an excellent way to figure out specific numbers for your circumstances. Each home consumes a different amount of electricity based on various factors. Having said that, if you take a 2,000 square foot home, the average solar panels cost equates to somewhere between \$15,000 and \$40,000.

Let’s look at an example to get a better idea of how much solar panels cost. The average home in the United States is 1,500 square feet with a monthly electricity bill of \$100. This means that the house needs a 6-kilowatt solar panel system with between 15 and 18 350-watt solar panels.

The estimated cost for a system of this size would be about \$18,000. If the system saved you \$2,500 per year on energy expenses, the payback period would be just over seven years until you would break even.