On average, water pumping accounts for 70% of the agricultural energy use in California. This number only grows during drought years. As electricity prices rise and drought drives farmers to depend more heavily on deeper wells and falling groundwater tables, the out-of-pocket energy costs of managing an agricultural operation grow. However, a majority of farmers still use electric pumps to draw their water as opposed to diesel engines—an 85% to 13% split, according to the 2013 USDA Farm and Ranch Irrigation Survey. Thankfully, while diesel engines do offer some unique conveniences, there remain a significant number of financial and environmental benefits to the current preference for electric-powered pumps.
Off-road diesel-powered pumps are more common in areas that are separated from the grid, where extending power lines to connect to the grid are often more expensive in the short run than the alternative–though annual savings from switching to an electric pump can offset these costs over time. Nevertheless, drawing power from fossil fuels like natural gas or diesel offers its own freedom from time-of-day electricity rates. Around one-third of water use on California farms happens during expensive peak hours, and while groundwater can be pumped during off-peak hours and kept in storage tanks until needed, the same can’t be said for booster pumps which need to be fired to pressurize water for irrigation. Booster pumps in California use nearly two-thirds the same amount of energy that is expended by well pumps, so diesel offers some benefits by allowing farmers to evade the costly power use of booster pumps during peak hours.
However, electric pumps have their own edge. Since there is no internal combustion involved in the pumping process, electric pumps need maintenance far less often than fossil fuel pumps, and last longer. Electric pumps also offer flip-the-switch convenience, and unlike engines, are not subject to costs from emissions regulations by air pollution districts. The environmental benefits of electric pumps are also significant, as electric pumps produce no local air pollutants, create less noise, and have lower greenhouse gas emissions over their lifetimes. This is in strict contrast to diesel engines, which are significant sources of nitrogen oxides and fine particulate matter that pollute the San Joaquin and Sacramento Valleys.
Electric pumps also provide flexibility to forward-thinking farmers, who can more easily transition their pumps to greener energy sources, including solar power, wind power, or power from burning methane released from cattle manure and crop residues.
Additionally, as the state transitions more of its power production to cleaner, renewable sources, the greenhouse gas footprint of electricity will fall even further.
This is not to say electric pumps are free of climate impacts. The grid is still powered primarily through fossil fuels. However, the efficiency at which the fuel is burned in a power plant vastly outweighs the efficiency of a small combustion engine, which means that a given unit of fossil fuels will generate more energy at a power plant than in an engine. Furthermore, electric pumps on the market usually draw more water per unit of expended energy than a diesel pump, as shown below.
Ultimately, the higher efficiency of electric pumps and the significant cost of diesel will usually make electric pumps the wiser option for most California farmers, despite fluctuations in electricity rates. A growing number of options are also becoming available to farmers to save water and energy, which may help mitigate possible growth in electricity prices. Several major utilities offer adjusted rates for agricultural pump users, including PG&E and Southern California Edison, and numerous programs by local, state, and federal agencies can save farmers money by helping them transition to more efficient irrigation systems and lower energy use.