Water Heating Efficiency Review
Intermatic WH40 Mechanical Water Heater Time Switch (40A, DPST) Review (2026)
A heavy-duty 240V timer that runs an electric water heater only when you need it.
Our verdict: Worth a low-risk try
★★★★⯨
$45-$60 · Amazon return policy applies
Check Today's Price →At a glance
| Category | Water Heating Efficiency |
|---|---|
| Our rating | ★★★★⯨ 4.6/5 |
| Price | $45-$60 |
| Availability | Check current price on Amazon |
| Returns | Standard Amazon return policy applies |
| Best for | Electric tank water-heater owners on time-of-use rates or with predictable daily hot-water schedules. |
Our take
The Intermatic WH40 is a mechanical 24-hour time switch rated 40 amps, DPST, for 208-250 VAC electric water heaters. Its yellow dial lets you set on/off trippers so the heating elements only run during chosen windows, idling the tank overnight or during work hours and, where time-of-use rates apply, shifting heating to cheaper off-peak periods. It is a proven, NEMA 1 indoor unit and is the standard hardware-store choice for adding scheduled control to a conventional electric tank. Installation involves 240V wiring and is best handled by an electrician.
What we like
- Cuts standby reheating by powering the tank only during set hours
- Helps shift electric load to cheaper off-peak time-of-use windows
- Rugged 40A mechanical mechanism with a long field track record
- Simple dial scheduling with no app, batteries, or network needed
What to keep in mind
- Requires 240V electrical work, so most buyers need an electrician
- Only applies to electric tank heaters, not gas or tankless units
- Mechanical dial offers no remote, smart, or automatic-adjusting control
Buy through Amazon and you're covered by their standard return policy. Check the live listing for today's price and real buyer reviews before you commit.
Sold on Amazon · Standard returns apply · Live price & reviews on the listing
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Frequently asked questions
Is Intermatic WH40 Mechanical Water Heater Time Switch (40A, DPST) worth it?
The Intermatic WH40 is a mechanical 24-hour time switch rated 40 amps, DPST, for 208-250 VAC electric water heaters. Its yellow dial lets you set on/off trippers so the heating elements only run during chosen windows, idling the tank overnight or during work hours and, where time We weigh real-world usefulness against price, and we note the downsides honestly. Check the live price and recent customer reviews on Amazon before deciding — both can change.
Where can I buy Intermatic WH40 Mechanical Water Heater Time Switch (40A, DPST)?
Through Amazon, where the standard Amazon return policy applies. We link to the current listing so you always see up-to-date pricing and availability.
Who is Intermatic WH40 Mechanical Water Heater Time Switch (40A, DPST) best for?
Electric tank water-heater owners on time-of-use rates or with predictable daily hot-water schedules.
Is Intermatic WH40 Mechanical Water Heater Time Switch (40A, DPST) the best in its category?
It's one we think is worth considering, but "best" depends on your needs and budget — compare it against the alternatives in our reviews before you buy.