What the LG DLEX3900* costs to run
ENERGY STAR certifies the LG DLEX3900* at 607 kWh/yr, about average for its category to run for its category.
That $114 is priced at 18.8¢/kWh, the average of all 51 state rates this site tracks. Your own state's rate is one click away.
Efficient, or not, for a clothes dryer
The category average is 572 kWh/yr; this model runs 6.1% above it, ranking 160 of 639 clothes dryers tracked here for running cost. That average is drawn from all 639 clothes dryers ENERGY STAR currently certifies, not an outside number, a $7/year gap from this model at the national rate. Full sourcing is in the sourcing notes.
Right next to it on the list
A rank or two either side of the LG DLEX3900*: LG DLEX3850* ($114/yr, 607 kWh/yr), then LG DLEX4000* ($114/yr, 607 kWh/yr).
Same brand, different models
Ranked 49 of LG's 144 certified clothes dryers, this sits between the DLHC1455* ($25/yr, the brand's cheapest) and the WSGX201H*A ($129/yr, its priciest).
Cost over its typical lifespan
NAHB's Study of Life Expectancy of Home Components puts a typical clothes dryer's service life at 12 years; run the LG DLEX3900* that long and it costs about $1,369 in electricity, on top of whatever it cost to buy.
Weighing a replacement
Efficient as certified clothes dryers go, $114/year is a reasonable baseline if you're comparing what else is on the market.
Worth comparing a few current certified models before deciding.
If you're keeping it
The LG DLEX3900* already costs $114/year to run; a repair bill on top of that is the kind of expense a protection plan exists to smooth out.
Where this number comes from
Two sourced numbers, nothing modeled: ENERGY STAR's certified kWh/yr for this exact model, and EIA's published state electricity rate. Ranked 160 of 639 certified dryers for running cost, the LG DLEX3900* is also worth reading with a caveat specific to this category: the methodology page explains why ENERGY STAR's own combined-energy figure for dryers can overstate the electric bill impact of a gas model.