Considering a solar energy system for your home? One of the first questions you’re probably asking is, “How many solar panels (often called “solar modules”), do I need on my roof?” To accurately calculate solar power needs with your installer and get the most out of your future system, you’ll need to provide them with accurate information about your energy usage.

Here are a few tips to consider when calculating your solar power needs.

Calculate Solar Power Needs, Step 1: Determine your local solar schemes and subsidies
One of the first things you’ll want to check out is the types of solar schemes and subsidies that are available in your region. In addition to tax credits and other rebates, different regions offer different types of incentive structures which are a key factor in deciding the size of your system. Your local SolarEdge-certified installer will be able to explain exactly what is available for you, but here are a few different concepts you should investigate:

Feed-in Tariff: In an area with feed-in tariffs (FiT), utility companies pay renewable energy producers (that’s you!) a fixed and above-retail rate for electricity supplied to the grid. To qualify, there will often be a deployment cap that will limit the size of your system.

Step 2: How much energy do you consume?
Another factor in deciding the size of your PV system is your own energy consumption. How much energy is used in your home on a typical day? Here are a few factors to take into consideration:

Number of people living at home
Heating and cooling devices
Appliances
Water heater
Lighting
Electric vehicles

Make sure to save a few recent electricity bills to show your potential installer so they can determine your consumption pattern, usually shown in kilowatt hours (kWh). Don’t forget that electricity usage might be higher in some months (i.e., if you use extra lights and heating during the winter).

A great way to understand and calculate solar power needs is to add an energy meter to your home. This will enable you to track your energy consumption habits even before you install a PV system, and thereby determine how large your PV system needs to be to offset your energy usage.

Step 3: Designing your solar energy system
Once your installer calculates your solar power needs, they will consider the following factors:

Your geographic location
Sunlight exposure
Roof size and direction if the system is being installed on your rooftop) or yard size for a ground-mounted system. For example, if you live in a location with lower sunlight exposure, a larger system might be needed to generate the same amount of power as a location with higher irradiance.
Since PV production does not exactly match energy usage, as solar energy is produced during the day and energy is typically consumed when families are at home in the morning and evening, you might opt to store your PV energy in a battery.

The type of PV system you plan to install is another important consideration when calculating how much solar power you need. For example, a solar inverter developed with module-level power electronics (MLPE) will enable each module to produce at its maximum individual output without being affected by other modules. This will also allow you to place more modules on the roof because they can be placed in different angles, directions and layouts, so that you can generate more energy for your own self-consumption or to feed into the grid.

When your installer calculates your system size and type, they can take into account both solar PV production and storage. Having an inverter with DC coupling (as opposed to AC coupling) allows you to store excess energy above the inverter rating. So, with oversizing, you could install a 5 kWp inverter, but have up to 7.75 kWp of solar modules, and then also add a 5 kWp battery. This would bring your actual total PV capacity to actually 12.75 kWp.

At SolarEdge, we’ve developed a web-based Designer tool for our installers to plan, build, and validate PV systems, taking all of the above-mentioned parameters (and more) into consideration. Location, climate, and other factors are used to design a 3D simulation of the roof that assists in creating a PV layout, complete with electrical design, production simulation, and everything needed to help future PV system owners understand and envision a solar-powered home.