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Calculating the size of your system
The size of the system you need depends on several factors:

  • How much energy usage you want to offset
  • Available space for the system
  • How much you want to spend

Solar Generation Systems

In Avista's electric service territory, a 1000W (1kW) well located, properly installed solar generation system could generate roughly 1100kWh of energy annually. The energy generated will vary depending on the positioning of the system with respect to the sun. Any trees or other obstructions will also impact the amount of generation.

Avista's average customer uses approximately 1000kWh per month. In order to offset 50% of the usage, you would need to install a system sized around 5.5kW. For 100% offset of the usage, a system sized around 11kW would be needed. To help calculate the size of your system, you can visit the National Renewable Energy Laboratory site.

To view your monthly energy consumption, visit your My Account, or find the information on your monthly energy bill.

Purchase and installation costs vary widely. For a detailed evaluation of the cost estimates and sizing, please contact a local solar vendor or contractor.

Wind Generation Systems

Wind generation systems are more difficult to site due to the variability of the wind resource. The background information necessary to size a system and estimate annual output requires more detailed analysis of the site. For a detailed evaluation of the cost estimates and sizing, please contact a local wind generation vendor or contractor.

Hydro Generation Systems

Hydro generation systems require approval from the Washington State Department of Ecology. For more information, please visit the Department of Ecology website.

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