The Economic Impacts of Deferring Electric Utility Tree Maintenance

"A study was conducted to examine the economics of deferring line clearance tree pruning. The cost of pruning a tree was found to increase significantly as it grows closer to, and beyond, the conductors. The amount of biomass, and thus disposal cost, also increases with the length of time a tree is allowed to grow. Predictive models were developed for three utilities to provide a means of projecting the total impact of postponing line clearance work on crew time and costs associated with pruning trees. For every routine maintenance dollar deferred, substantially more than one dollar must be spent in subsequent years to re-establish the preferred cycle. The specific amount of this increase is utility dependent and is affected by production costs, tree growth rates, site characteristics (dbh and type of pruning), etc. An additional adjustment would be necessary to allow for an increase in disposal costs resulting from a larger amount of biomass removed. If funding reductions are not offset with larger expenditures in subsequent years, tree maintenance cycles are rapidly extended. Modeling a 20 percent annual funding decrease resulted in extending one utilitys cycle from 5 years to 9 years over a 12-year period. These estimates do not take into account the impact that deferred line clearance work has on service reliability, service restoration costs, and the amount of time spent on hotspotting and responding to customer requests for unscheduled maintenance."