System Sizes and Costs :: Residential

System Size
Solar power systems are measured in kilowatts (kW). Your electric usage is measured in kilowatt-hours (kWH). In Ohio and surrounding areas, 1 kilowatt of solar array produces approximately 95 kilowatt-hours per month. To determine the size system that you will need, Third Sun will need to look at your electric usage. Current kilowatt-hour usage can be found on your utility bill, along with a summary of your last 12 months usage. An advantage of utility-interactive (net metered) systems is the option of selecting a system that provides only a portion of your energy from the sun if project size is limited by roof space or budget.

Typical System Prices and Information
Third Sun can supply a system to fit every house and budget. Below are examples of three typical sizes of systems, their estimated performance, the space required and the net cost after incentives. Larger, smaller and other sized systems are available. Third Sun works with each customer to determine the best sized system based on roof size, energy needs and customer budget. Larger systems cost less per kW as fixed costs are spread over larger projects.

System Size	3.15 kW	5.4 kW	7.2 kW
Monthly energy	299 kWh	513 kWh	684 kWh
Square footage	190	325	430
Net cost	$9,903	$14,278	$17,079

Shading and specific site variables will affect monthly output.

Roof square footage based on Sunpower solar modules.
Net cost based on full service installation on typical home with roof mounting. This cost calculation includes the 30% Federal tax credit and $3,000 per kW Ohio Energy Office Rebate (only available for customers of an Ohio Public Utility).

Placement of Solar panels (and shade)
Each 1 kilowatt of solar panels needs 60-100 square feet of space, depending on brand of solar module. Solar panels are usually roof mounted, and this is the most economical. They may also be standalone on the ground, or mounted to other yard structures such as gazebos or barns. For your system to perform at its maximum potential, avoiding shade is very important, mostly between 10-4, and less important in the (less productive) winter months. Optimally, your solar panels should have unobstructed southern exposure. Orientation to the east or west is possible, but will reduce performance (our computer analysis can give you a good prediction of this, as well as the effects of any shading). Even a slight amount of shade from trees, buildings, pipes, chimneys or obstructions can have an impact on production.

Batteries and Backup Power
With a battery free on-grid system, utility power outages still result in a power outage for the renewable power system owner. This is because an on-grid system is required to shut down when there is a power outage, eliminating safety concerns for utility workers. It is possible for a battery bank to be added in order to produce backup power in times when there is a utility power outage. Adding a backup battery bank system will increase a homes energy security, but will add cost to a system. It also results in a less efficient system. Third Sun has done many off grid and grid tied systems with battery backup, and we would be happy to discuss the specific pros and cons of adding backup capacity to your system.