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Sizing a Solar System to Meet Your Energy Needs

Posted by AllEarth Renewables on June 3, 2015 in Sizing a Solar System, Residential Solar, Consumer

Learn how to size a solar system based on your household's energy needs.

When considering going solar, it's important to match the size and scope of your solar system to the current and projected energy needs of your household. Researching your options for a solar system comes down to two variables: what energy needs must be met, and what the solar resources available in your geographic area are.

Installing the right size system will allow you to meet your household needs and also ensure a good long term return on investment. If you spend some time collecting information and being clear on your goals, you can be sure to get a system that offers ample power and good value.

Household Energy Usage

To establish a baseline of your energy usage you need to look no further than your electricity bills over the past year. It's beneficial to review both the highest energy requirement as well as the total for all 12 months to know precisely what's needed. On your monthly bill will be a total of kWh for the billing period. Adding up your usage for 12 months will provide you with your annual energy usage, and give you a baseline for determining how much energy you'll need from your solar system. 

It is also important to look into the future and consider any changes that may impact your energy needs. These include such things as converting your heat and/or hot water to electricity, additions or subtractions to the number of people living in the house, the addition of a plug-in electric car, or new electrical appliances like a heat pump or central air conditioning.

Energy Production Goals

Once you know your energy usage and have projected future use, you need to be clear on your goals for the solar system. The size and design of your solar system will be heavily influenced by the amount of energy that you want the system to produce.

Are you looking to generate enough power to offset your annual energy usage or do you want to simply offset a certain percentage of your energy requirements? When considering this goal it is important to remember that solar system production will not necessarily follow with your energy consumption in any specific period. Your focus should be what percentage of your annual energy usage you're looking to offset with a solar system, or your target annual energy production.

Solar System Efficiency

Once you have established a goal for the amount of power you hope to generate from your solar system, you can now start to define the size of the system you will need. Different types of solar systems will have different production levels, especially depending on your geographic region and its weather conditions. Roof-mount solar can have a high production level if you have a roof with southern exposure, but a ground-mount system in an unshaded area, especially one that tracks the sun, could produce up to 45% more energy depending on your region. Be sure to have your installer is thinking of your installation size in terms of kWh production rather than kilowatts installed--two ground-mount systems of the same size and in the same location, one fixed and one tracking, will have very different energy outputs. 

Other Variables

Once you have a good idea of your energy demand and the general size of the system to meet your targets, it's important to keep in mind other factors that might help guide your decision when choosing the right solar system for your needs.

Take a look at the tax incentives/rebates offered by the federal government, your state government, and the local power company--programs like the federal income tax credit can help offset the cost of your system significantly.

There are also a number of ways to finance a system, ranging from an outright purchase to long-term lease and power purchase agreement programs, so be sure to explore all options offered to you by your dealer to determine what will make the most sense for you financially.

Finally, every state and locality has its own set of policies and options for net metering, grid-connection and permitting requirements. Net-metering regulations can play a big role in determining the size of your solar system, and permitting and grid-connection rules can also factor into your decision. 

Working with a local solar dealer who has some understanding of these options, and understands how to size a system in terms of kWh production versus kilowatts installed, will ensure that you ultimately find the right system to meet your energy goals.

Curious about your solar options? Interested in learning more about choosing the right system for your household's energy needs? Find out everything you need to know in our Consumer Guide to Investing in Solar.

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