How does rooftop solar work?

Different companies pitch solar panels different ways so it's important to understand how a photovoltaic installation works and impacts your electric bill before committing. Some things to keep in mind:

• DPU does not partner with any solar companies
• Every Los Alamos electric customer pays service fees according to class (i.e. residential or commercial)
• Solar panels do not reduce the retail rate per kWh for electricity provided by DPU
• Depending on how much solar power is produced, solar customers may receive credits at the wholesale rate, not the retail rate
• DPU does not "bank" solar generation credits to apply to future bills
• Solar panels only produce electricity when the sun is shining
• Los Alamos County utility customers with rooftop solar do not contribute to the Los Alamos National Laboratory electric grid at any point. LANL has its own electric distribution system.

If you're interested in the basics, please watch this video from the U.S. Department of Energy.

Energy 101: Solar PV

This diagram illustrates what happens once solar rays hit rooftop solar panels. You may click on the image to see an enlarged version.

(JPG, 158KB)

The basics

Your solar panels will supply energy first to your home. DPU does not meter this energy and no charges apply for solar energy used directly by the house. This energy represents a return on investment (ROI) for the avoided cost of buying electricity from DPU.

If your solar panels produce more energy than is used by the house, that energy will flow through the electric utility meter to the grid. It is essentially energy supplied to DPU. On your utility bill, you will see a credit for this energy at the wholesale cost.

If your house needs more electricity than your solar panels are providing at any point in time, DPU will provide electricity to you from the grid just as if you didn't have solar panels at all. This energy supplied by DPU will be billed to you at the retail rate. 

Storage

Most customers do not have batteries to store energy produced by their solar panels. As such, electricity used at night and on cloudy days will be supplied by DPU. Once energy is produced, it is available immediately and can't be "banked" for later. You should expect to see variances in your monthly charges due to seasonal variations impacting solar production.

System Sizing

Before you install solar panels, DPU's Electric Distribution staff will determine sizing for your photovoltaic system based on your current annual electric consumption. Customers making household electrification improvements may request a variance to the ultimate size.

Billing

Your bill is reduced by the amount of electricity that you didn't need to purchase from DPU. If you still produced more than your house used, DPU will pay you the average wholesale cost for that energy, which is in line with how purchased energy from any other outside resource is treated. Solar customers should not expect to eliminate the electric charges on their utility bills. All electric customers--those with solar and those without--impact DPU's electric grid and infrastructure. Through DPU's electric rate structure, all customers are charged to cover the expense of that impact. 

How does DPU's credit to rooftop solar customers compare to that of other nearby utility providers?

Each rate is intended to cover a different expense born by the utility in providing electricity to the Los Alamos County community. As a public power, DPU sets rates to cover costs, not bring in profits. All electric customers impact utility operations and the electric infrastructure around them and must be charged accordingly.

Monthly Service Charge

The monthly service charge is collected to cover the costs of maintenance and replacement of critical infrastructure. Every electric utility customer in Los Alamos pays this charge.

Retail Rate

This is the per-kilowatt-hour rate charged to every residential electric customer for power delivered to their homes. It covers everyday operational costs of the utility as well as the costs of power purchased by DPU.

Wholesale Credit

This is the per-kilowatt-hour credit returned to rooftop solar customers whose excess energy production was delivered to the grid. This credit is equivalent to the current wholesale cost for all energy delivered to the distribution system, whether that energy comes from DPU's resources, purchased power or rooftop solar customers.