What does a battery trickle charger cost to run?

Run the numbers on your own use

Change any of these and the figures update. The defaults are the typical case described above; your rate is the input that moves the answer most.

Why this is lower than the number you will see elsewhere

Almost every published answer to this question multiplies the rating on the label by the hours the appliance is switched on. For a battery trickle charger that gives 108 kWh a year, or $20.

A modern maintainer floats and switches off, waking periodically to top up. An old unquenched trickle charger draws continuously and never stops.

The arithmetic, step by step

Nothing here is hidden, so you can check it or change it. Working in the order the formula runs:

1. 25 W — what it draws while it is actually drawing. This is the rating on the plate.
2. × 35% — the share of its in-service time it is really pulling that. A modern maintainer floats and switches off, waking periodically to top up. An old unquenched trickle charger draws continuously and never stops.
   That gives 9 W averaged across the hours it is on.
3. × 24 hours a day × 180 days — Maintaining a seasonal vehicle’s battery through the off-season.
   9 × 24 × 180 ÷ 1,000 = 38 kWh a year.
4. × 18.34¢ — the US average residential rate for June 2026.
   38 kWh × 18.34¢ = $6.93 a year.

Change any assumption in the calculator above and every figure on this page moves with it. The two that matter most are your rate, which varies 4× across the country, and the hours — the duty cycle is a property of the appliance, but the hours are a property of you.

How sensitive is that number?

A single figure invites more confidence than it deserves. Here is the same appliance under assumptions either side of the default, so you can see how much of the answer is the appliance and how much is the guess about how you use it.

Everything else held at the default. The spread here is the honest error bar on the headline figure.

What it costs per hour, day and month

At 18.34¢ per kWh, the US residential average for June 2026.

The thing worth knowing

The difference between a smart maintainer and an old trickle charger is roughly ten to one in electricity, and rather more than that in battery life — a continuous trickle boils the electrolyte off over a winter. If the unit has no float stage, it is costing you money and a battery at the same time.

Against e-scooter charger

A modern microprocessor-controlled maintainer, or simply disconnecting the battery for storage, which costs nothing at all. In numbers: a battery trickle charger costs $6.93 a year on these assumptions, and e-scooter charger doing a comparable job costs $14 — a difference of $6.64 a year, or $66 over ten years at today’s rate.

Both at 18.34¢/kWh, each on its own standard usage assumption. Ten years is roughly the service life of either.

What it costs in your state

The appliance is the same everywhere; the rate is not. Running this battery trickle charger costs $20 a year in Hawaii and $4.96 in Nevada — a difference of 4×.

Cost of running one battery trickle charger for a year, by state. Residential average price, EIA June 2026.

Other EV charging costs

• EV charging (Level 1 wall socket)

  $687 a year

  The same 11,100 miles a year on a standard outlet, including about 15% charging loss.

• EV charging (Level 2 home)

  $649 a year

  11,100 miles a year at 3.5 miles per kWh on a 32 A charger, including about 10% charging loss.

• Golf cart charger

  $133 a year

  Charging a 48 V lead-acid pack after most days' use.

• Engine block heater

  $110 a year

  Plugged in overnight through a cold-climate winter.

• E-scooter charger

  $14 a year

  Charging a mid-size commuter scooter most days in the riding season.

• E-bike charger

  $12 a year

  Charging a 500 Wh battery from low most days through the riding season.

Questions

Source: U.S. Energy Information Administration, Electric Power Monthly, Table 5.6.A, June 2026. U.S. Government work, public domain.

How every figure on this page is computed · Where the data comes from