Model
Lg WM3420C*
Rank #41 means 40 of the 388 washing machine models we track cost less to run each year; the 95th efficiency percentile means it uses less energy for its size than 95% of those models.
What does the Lg WM3420C* cost to run per year?
Do the math and the Lg WM3420C*'s $15/yr puts it at rank #41 of 388, one of the more affordable washing machine models we track to keep running. Normalized for capacity, it ranks ahead of 95% of washing machine models we track on efficiency, an exceptional showing for the class. The IMEF figure of 3.1 on this model captures integrated modified energy factor, the main efficiency lever ENERGY STAR tracks for this class.
Immediately around it on the leaderboard, the Maytag MHW8150E** at $15/yr runs a little cheaper and the Whirlpool WFH5424S** at $15/yr runs a little more, a sense of how tightly models are packed at this point in the ranking. A washing machine typically stays in service for somewhere around 10 years; over that span, the Lg WM3420C*'s $15/yr adds up to roughly $150 in electricity alone, before purchase price or repairs.
By the numbers
The Lg WM3420C* normalized against its whole class, so each figure means something.
What it costs you over time
Running cost is an every-year number, so it compounds. At $15/yr, here is what the Lg WM3420C* adds up to before purchase price, water, or repairs enter the math.
Left running for a decade at today's US average rate, the Lg WM3420C* costs about $150. That is roughly $50 less than the class median, which would run closer to $200 over the same ten years.
How the Lg WM3420C* compares
The washing machine class we track runs from $7 to $58 a year. At $15/yr, it runs about $5 a year cheaper than the class median of $20, and it is about $8 a year more than the cheapest washing machine to run at $7.
What drives its running cost
At 4.5 cu ft, the Lg WM3420C* is a mid-size washing machine for its class, which spans 1.9 to 6 cu ft with a median of 4.5 cu ft, right in the middle of the capacity range, so capacity is roughly a wash compared with the rest of the class. Beyond size, its IMEF of 3.1, above the class median of 2.76, is the class's own efficiency yardstick, integrated modified energy factor, and it is what separates two similarly sized models with different running costs.
- Spin and wash efficiency (IMEF). A higher Integrated Modified Energy Factor means the machine wrings more useful washing (and a drier spin) out of every kilowatt-hour and gallon it uses.
- Drum volume. Drum volume sets the ceiling on how much a single cycle can wash, and it is usually the first driver of a washer's per-cycle energy use.
- Water heating. Cycle temperature, more than drum size, is usually what separates a cheap wash cycle from an expensive one on models with an internal water heater.
Common questions
Is the Lg WM3420C* cheap to run?
Yes, relatively. At $15 a year it ranks #41 of 388 washing machine models we track, in the cheaper part of its class to run.
How much does the Lg WM3420C* cost per month?
Roughly $1.24/mo, spreading the $15/yr estimate evenly across twelve months at $0.1856/kWh. Actual monthly bills swing with your rate and usage pattern.
How is this running-cost figure calculated?
We take the model's published annual energy use of 80 kWh from ENERGY STAR and multiply it by the US average residential electricity rate of $0.1856/kWh, giving about $15 a year. It is an electricity-only estimate and does not include purchase price, water, or installation.
How efficient is the Lg WM3420C* for its size?
95th percentile once size is factored in. That means its size-adjusted efficiency is a real factor in the running-cost figure above; its capacity plays a large role too.
Cheaper to run in the same class
| Rank | Model | Cost/yr |
|---|---|---|
| 40 | Maytag MHW8150E**4.5 cu ft | $15 |
| 39 | Midea MLHW31S2BWW2.7 cu ft | $14 |
| 38 | Midea MLHW31S2BBW2.7 cu ft | $14 |
| 37 | Midea MLHW31S2BB2.7 cu ft | $14 |
| 36 | Midea MLHW27S7BWW2.7 cu ft | $14 |
Source
ES_1118034_WM3420C*_01132026085726_80285086View certified washing machine listingsENERGY STAR data as of July 2026Lg and WM3420C* are used here for identification only and are not endorsements. Figures are computed by WattWise Labs from public ENERGY STAR data, not measured in our own lab.