Intermatic 20-Amp 24-Hour SPST 1-Circuit Digital Time Switch

The Verdict

If you need to automate a heavy electrical load—think water heater, pool pump, or driveway heater—the Intermatic 20-Amp 24-Hour Digital Time Switch earns its place in your panel. This isn’t a smart-home gadget with an app; it’s a workhorse timer built for reliability.

What You Get

The box contains the DT101 timer unit itself, a mounting bracket, and a quick-start guide. It’s designed to mount inside a standard single-gang electrical box or directly on a wall surface. The unit measures about 3.75 inches square and 2.5 inches deep—compact enough for most mechanical rooms. The front panel opens to reveal a small LCD screen and four rubberized programming buttons.

Performance and Build Quality

The headline feature here is the 20-amp rating. Most programmable timers top out at 15 amps, which means you’re limited to about 1,800 watts. This Intermatic handles up to 2,400 watts on a 120-volt circuit or 5,760 watts at 240 volts. That’s the difference between automating a lamp and automating your actual water heater.

The SPST (single-pole, single-throw) configuration is simple: one circuit, on or off. You get up to 12 on/off events per day, which is plenty for most applications. The 24-hour cycle means you set a weekly schedule that repeats daily—no complicated 7-day programming to wrestle with.

Battery backup is a genuine differentiator. The built-in rechargeable battery holds your schedule for up to four hours during a power outage. When the lights come back on, the timer knows what time it is and resumes your program without you touching a button.

Buyers consistently mention the reliability. One reviewer noted, “Installed this on my water heater three years ago and haven’t touched it since. It just works.” Another said, “The red indicator light is a small thing, but being able to glance at the panel and know the circuit is live saves me from second-guessing.”

Where It Falls Short

The most significant limitation is the neutral wire requirement. This timer needs a neutral connection to power its internal clock and display. If you’re replacing an old mechanical timer in a switch box that only has line and load wires, you’ll need to run a new neutral or skip this unit entirely. Several reviewers hit this wall. One wrote, “Didn’t realize I needed a neutral until I opened the box. Had to call an electrician to run one.”

The programming interface is functional but dated. The two-line LCD isn’t backlit, making it hard to read in dim mechanical rooms. The buttons are small and require a firm press. It’s not intuitive on day one—plan to spend ten minutes with the manual before your first setup.

Who Should Buy This

This timer is ideal if you’re a homeowner or electrician automating a heavy 240-volt load like a water heater or baseboard heater. It’s also a solid choice for controlling outdoor lighting circuits that draw serious wattage. If you need 7-day programming or smartphone control, look elsewhere. If you need something that will still be working in a decade, this is your pick.

FAQ

Q: Does this timer work with a 3-way switch setup?
A: No. This is SPST only—one switch location controlling one circuit. For 3-way applications, you need a different model.

Q: Will it control a 240-volt water heater directly?
A: Yes, up to 20 amps. That’s the most common use case for this timer. Just verify your water heater’s amperage draw before installing.

Q: Is an electrician required for installation?
A: If you’re comfortable working in an electrical panel or junction box and have a neutral wire available, it’s a straightforward DIY job. If you don’t have a neutral, call a pro.

The Verdict

Buy it if you need reliable, heavy-duty load scheduling and don’t mind a basic interface. Skip it if your wiring lacks a neutral or you want app-based control.

With 210 ratings averaging 4.2 stars, the Intermatic DT101 has proven itself as a dependable workhorse. It’s not glamorous, but it does exactly what it promises—and keeps doing it for years.

Rating: 4.2/5

Where to Buy

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Last updated: 2026-08-06. Ratings and prices current as of review date. Verify on Amazon before purchasing.