Truckee Donner Public Utility District

At TDPUD, we buy the power that supplies our town with electricity. It may sound like a simple transaction, but there is a lot that goes into making sure the lights turn on when you flip a switch. 

From customer demand to available resources, there is a lot to consider when determining how to supply Truckee’s residents, visitors and businesses with enough energy to satisfy all of our customers’ needs every minute of the day. The way energy planning works, we actually have to know the exact amount of energy and where we are getting it from for every 15-minute increment of the day!

TDPUD recently completed its first ever integrated resource plan, which incorporates the many variables of power purchasing and energy demand to create a roadmap that will allow TDPUD to best plan for our community’s future. Read on to learn more about how we plan for our customer’s energy needs, as well as the role our customers play in that equation.

How do we know how much energy to buy?

Our electric power supply team is constantly analyzing how much energy our customers use, and using that data to schedule short-term energy deliveries, as well as forecast Truckee’s future needs.

But that amount changes from season to season, from week to week, and is even dependent on the time of day. We are a winter, weekend/holiday, and nighttime peaking utility, which is actually the reverse of most areas in California. Most utilities see air conditioning drive up use in the summer and offices drive up use during the day. Instead, we see heating drive up use in the winter and visitors flock to our area on the weekends and holidays. 

Being able to accurately forecast our energy demand in the future is the crucial first step to building a robust energy plan. It touches everything from the amount of power we will need to purchase, to the infrastructure we will need to maintain, to accommodating the location of future development in our town. 

It’s important that our customers only use the electricity that they need, so that we can forecast and plan accurately. If you use it, we supply it, so if our customers’ demand exceeds what we’ve planned for, we still need to fulfill our obligation to provide power.

How do we know how much energy is going to cost?

Future energy costs can be a difficult thing to predict, as there are many variables that can shift markets in unforeseen ways, but we do our best to analyze trends, monitor global markets and events, and pursue contracts that make sense for both our climate goals, focus on affordability, and commitment to reliability.

We pursue contracts or power plant ownership with various energy producers to lock in power costs at a set rate or proforma for a certain period of time. This allows us to budget and set rates as effectively as possible. For most of these contracts we are the co-owners of an energy generation plant, but in other cases we sign short-term contracts for energy purchase. For example, we have ownership stake in the Red Mesa Tapaha Solar Farm and the Horse Butte Wind Farm. These two projects supply nearly 30% of our total annual energy procured.

However, sometimes interruptions to our planned power purchases or unplanned outages at the power plants that we own, can cause us to have increased exposure to the open market. In Winter 2022-23, the delayed completion of the Red Mesa Tapaha Solar Farm as well as interruptions in power generation at other contracted locations forced us to buy more market power than planned, all while natural gas prices spiked due to colder than average temperatures, the Ukrainian War and other variables. This created a $3M unplanned expenditure that we later had to recoup through a rate increase. In late 2023, a turbine blade at Horse Butte Wind was struck by lightning, causing damage that took two months to repair.

Power costs also vary at different times of day. Energy is generally cheaper for us to procure during the day when solar production is at its highest, versus dusk and dawn, when we rely on our hydroelectric, wind and natural gas sources of energy.

9am-3pm: cost is down, energy is “greener.”

5-9am and 4-10pm: cost is up, energy is less “green.”

10pm-5am: cost is in the middle, energy is the less green than the daytime.

What types of power generation does TDPUD’s energy currently come from?

Currently, TDPUD’s energy mix consists of wind, solar, biomass, hydroelectric and natural gas, as well as the mix of "unspecified" sources available on the open market. We are exploring additional carbon-free resources to add to our portfolio, like geothermal, energy storage, concentrated solar and hydrogen.

What are the differences between the types of carbon-free sources TDPUD purchases energy from?

An important factor that characterizes carbon-free resources is whether they are baseload or intermittent.

Baseload: these are resources that will generate electricity as long as the power plant is on, meaning they don’t rely on outside variables to initiate production. Examples include geothermal and biomass.

Intermittent: these are resources that depend on an outside force to generate power. Because of that it can be difficult to predict how much power it will supply. Examples include wind, solar and hydroelectric.

How do clean energy regulations affect the kinds of power that TDPUD buys?

In 2018, the California legislature passed S.B. 100, which said California utilities will procure power from 100% renewable and carbon-free resources by 2045, and established benchmarks to ensure progress toward that ultimate goal. The first major requirement is for utilities to have 60% of their portfolio come from renewable resources by 2030, which TDPUD has already achieved.

However, where the law gets complicated in practice is with determining what qualifies as renewable and/or carbon-free energy in the eyes of the California Energy Commission, the state regulatory agency that oversees compliance with this policy. The biggest hurdle to accomplishing the 100% goal will be in having enough reliable, baseload carbon-free energy to meet the state’s needs at night and when intermittent resources are underproducing.

The chart below shows TDPUD's plan to meet California's RPS and GHG requirements.

How do we forecast what Truckee’s needs will be in the future?

TDPUD’s net demand growth has been fairly steady over the past decades, amounting to about 1-2% per year. But given the major switch to electrification in homes and the proliferation of electric vehicles, we knew that the next decade will not look the same. This was part of the reason for creating TDPUD’s first-ever Integrated Resource Plan.

As part of our new Integrated Resource Plan, our consultants, Aspen Environmental Group and Flynn RCI, estimated what our energy demand will be by factoring in current usage, electrification trends, our community’s growth and more. They presented us with three potential scenarios to consider as we plan for the future to cover a range of potential demand increases.

The Integrated Resource Plan doesn’t just consider the projected increase in energy demand. It also includes energy efficiency goals to help offset that load growth. Some of that has to do with how we operate the utility, but there is also a lot of power that customers can help us keep our load growth in check, even while they electrify their homes and vehicles. 

How can TDPUD customers help us accurately plan for the future?

The easiest way to help us is to only use the energy that you need and only when you need it. This will help us stay as close to our forecast as possible, which means we won’t have to buy power outside of our contracts to fulfill the community’s needs.  If customers can shift their energy usage to the time of day where energy is the most carbon-free and the least expensive, everybody wins.

Customers should request a free energy audit to better understand where deficiencies in their home might be, and learn how to make their homes more energy efficient, through both appliance upgrades,  minor repairs and behavior changes. If you plan on making energy efficient upgrades, make sure to look into our energy efficiency rebate programs to get money back on fixes like duct repairs and new windows, and building envelope testing.

If you are planning to electrify your home with new appliances or install an electric car charger, engage with TDPUD first. Not only can we direct you towards rebates to save money on these purchases, but if we know that your electric load is going to increase then we can factor that into our demand forecast. Energy planning works best when we all work together.

How can TDPUD customers take control of their own energy usage and costs?

We will be debuting a new time-of-use electric rate this year, which serves to incentivize customers to shift their energy usage to off peak times with financial benefits. Energy costs us less to procure during the day, but that’s usually when we see the least amount of usage among our customers. The TOU rate is an opt-in program, and provides customers with a less expensive electric rate during off peak hours. We’re passing along the savings we receive for purchasing power when it is cheaper and “greener.” However, customers enrolled in this program will be charged a higher rate for electricity used within the peak period (4-9pm).

How will the integrated resource plan help TDPUD?

The IRP helps us better envision the nexus of power demand and supply in Truckee for the next 15 years.

This chart shows how our demand will likely grow, accounting for a variety of sources for that increase. It also shows how we plan to offset this growth with energy efficiency, shifting load to off-peak times, and new, local solar production.

The IRP is a living document. It sets us on a great path, but we don’t get to kick back and coast for the next decade. We will still be monitoring and updating these figures and making adjustments where necessary, to ensure that we can continue to provide reliable, affordable, sustainable energy for our community into the future.

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