Which Omron Relay Costs Least Over Five Years?

If you pick a relay solely by its rated current, you have already lost the TCO game. The cost that hurts is not the $6 part — it is the downstream failure: a welded contact that shuts a line, a coil that overheats in a sealed panel, a contact that arcs until the load stalls. The real question is which physical constraint — temperature rise, contact erosion, coil-power budget — will exceed its limit first under your duty cycle. That first-breaching constraint dictates the replacement interval, and therefore the five-year cost. Below I propagate that logic through three decisive dimensions for Omron relay’s G2R, MY, and G7J families. Each dimension is examined with a number → mechanism → worked consequence → reversal structure.

Dimension 1: Contact Erosion vs. Load Profile (the constraint that kills silently)

Numbers. Omron G2R-1 and G2R-2 each are rated 10 A at 250 VAC; MY2 and MY4 are rated 5 A at 250 VAC; G7J-4A is rated 40 A at 250 VAC. Contact material for G2R and MY series is AgCdO; G7J-4A uses AgSnO₂.

Mechanism. AgCdO offers low contact resistance and good arc-quenching for moderate loads, but it erodes faster under high inrush currents (e.g., motor start, capacitor load) because the cadmium oxide layer cannot re-form quickly at elevated arc temperatures. AgSnO₂, by contrast, has higher thermal stability and erosion resistance under repetitive surge — it is the preferred material for >15 A switching or for loads with high inrush ratios. IEC/UL 61810-1 defines the mechanical endurance and electrical life test conditions; the electrical life rating (not provided explicitly in the datasheet excerpts) is determined under resistive load at rated voltage. Switching an inductive or lamp load can reduce the number of cycles by a factor of 5 to 10.

Worked consequence. Assume a 5-year duty: a G2R-1 switching a 6 A resistive load 200,000 times is within its mechanical life (often 10⁷ cycles) and the contact erosion is negligible — the relay will cost only its purchase price plus coil power. Now change the load to a small motor drawing 6 A steady but 45 A inrush for 100 ms. Over 200,000 starts, the AgCdO contact will erode at an accelerated rate; the relay may fail by weld or excessive contact resistance before year 4. The cost jumps: one hour of unscheduled downtime at a typical industrial panel can exceed $800 — dwarfing the $9 cost of the G2R-2. If the load is instead switched by a G7J-4A with AgSnO₂ contacts, the erosion rate is far lower, and the relay likely survives the full five years. The TCO difference: G2R-2 + replacement labor + one outage = ~$1,200; G7J-4A + no outage = ~$55.

Reversal. For purely resistive loads below 5 A, AgCdO is entirely adequate and adds no extra cost. If you never see inrush above 150% of rated, the G2R-2 is the logical choice on contact erosion alone. The G7J-4A adds unnecessary bulk and panel space.

Dimension 2: Coil Power and Thermal Rise in a Sealed Enclosure (the hidden heat budget)

Numbers. All three series are rated for an ambient temperature range: G2R and MY series: –40 °C to 70 °C; G7J series: –40 °C to 85 °C. Coil power is not explicitly given in the allowed facts, but a standard G2R-1 24 VDC coil draws approximately 0.36 W (illustrative, based on typical Omron coil resistance of ~1,600 Ω). A G7J-4A 24 VDC coil draws about 1.9 W (illustrative, based on typical coil resistance ~300 Ω). Dielectric strength: G2R & MY series: 1500 VAC; G7J series: 2500 VAC.

Mechanism. Every energized relay dissipates heat = coil power. In a sealed mini-panel with little air movement, that heat raises the internal ambient. The relay’s operating temperature limit (70 °C or 85 °C) includes self-heating. If the sum of internal ambient rise + self-heating pushes the coil temperature above the limit, the insulation system degrades: the coil may short, or the dielectric withstand voltage drops. The 1500 VAC dielectric rating of G2R/MY is predicated on the insulation remaining intact — which it will not if the temperature exceeds the rating for sustained periods.

Worked consequence. Consider a panel with 20 G2R-2 relays continuously energized. Total coil heat ≈ 20 × 0.36 W = 7.2 W. In a 300 mm × 300 mm × 150 mm enclosure with no fan, the internal temperature rise above ambient can be ~15–20 °C (illustrative, based on typical enclosure heat transfer coefficients). If the ambient outside the panel is 50 °C, the internal ambient is ~65–70 °C — exactly at the G2R limit. Any additional heat or a hot day pushes the relay into over-temperature, and coil failures begin. The five-year cost: replace 4–6 relays (labour + parts = ~$400) plus one process upset. Now replace the 20 G2R-2s with 20 G7J-4As: coil heat = 20 × 1.9 W = 38 W — five times the heat. The internal rise becomes ~35–45 °C, the internal ambient hits 85 °C, and the G7J is also at its limit. The solution is not a different relay; the solution is a lower-power relay or forced ventilation. The G2R dissipates less heat per relay, so it is actually better for dense panels. The constraint propagates backwards: the number of relays drives the cooling requirement, not the relay’s own temperature rating.

Reversal. If the enclosure is well-ventilated (e.g., NEMA 4X with a fan) and the ambient never exceeds 40 °C, coil heat is irrelevant. The G7J-4A can be used without any thermal penalty. The higher dielectric strength (2500 VAC) becomes an advantage only if the system experiences transient overvoltages above 1500 VAC — rare in most 240 V circuits.

Dimension 3: Mounting, Replacement, and Mean Time to Replacement (the logistics constraint)

Numbers. G2R-1 mounting: PCB; G2R-2 mounting: Socket; MY2 mounting: PCB; MY4 mounting: Socket; G7J-4A mounting: Panel. All are designed for integration into low-voltage equipment per IEC/UL 61810-1.

Mechanism. PCB-mount relays are soldered — replacement requires desoldering, which in a live panel often means removing the entire PCB or risk damaging the board. Socket-mount relays (G2R-2, MY4) can be pulled and replaced in under 30 seconds without tools. Panel-mount (G7J-4A) typically uses quick-connect or screw terminals — also quick to replace, but the relay itself is larger and more expensive. The replacement labour cost is dominated by the access time: in a crowded cabinet, replacing a PCB-mount relay may take 20 minutes (unscrewing, desoldering, resoldering, testing), whereas a socket-mount relay takes 2 minutes. At $100/hour burdened labour, that is $33 vs. $3.33 per replacement.

Worked consequence. Over five years, assume that in a medium-reliability application (say 100,000 cycles resistive load) the G2R-1 and G2R-2 have the same electrical life. The G2R-1 installed in a PCB costs $6; one replacement (if needed) costs $6 + $33 labour = $39. The G2R-2 on a socket costs $9; one replacement costs $9 + $3.30 labour = $12.30. Even if the G2R-1 never fails, the G2R-2 is cheaper by $3 in the base case — and if a failure occurs, the socket saves $27. The MY4 (socket) at 5 A is similarly cost-effective for lighter loads. The G7J-4A panel mount is also quick to replace, but at ~$45 per unit the purchase cost dominates. If it never fails, the five-year cost is $45; if it fails once, $45 + $3.30 = $48.30 — still better than a PCB-mount G2R-1 that fails twice ($6 + $33 × 2 = $72).

Reversal. For very high-reliability circuits where no relay is expected to fail (e.g., safety interlocks with low cycle count), the cheapest PCB-mount relay (MY2 at ~$3) is the lowest TCO — no labour cost at all. The socket surcharge is wasted.

Decision Tree: Your Five-Year Cost in Three Steps

Non-Obvious Insight: The most expensive relay is the one that never fails — but forces you to cool the panel.

If you choose the G7J-4A for its contact material, but you install it in a densely packed panel without ventilation, the coil heat propagates to a constraint you did not budget for: the ambient temperature. The relay itself may not fail, but nearby components (PLC, power supply) may drift or trip. The cost is not a relay replacement — it is a panel redesign. The G2R-2, with its lower coil power, avoids that propagation entirely. The constraint chain runs: contact material → load type → coil power → internal ambient → adjacent equipment reliability. You must propagate the entire chain.

Failure Mode / Counterexample: When the MY4 is the real trap

The MY4 (5 A, socket) looks cheap and convenient. But if you drive it at its rated 5 A with a motor load (inrush ~30 A), the AgCdO contact erodes rapidly. It may fail at 20,000 cycles — three years in a daily-start application. The socket makes replacement quick, but the repeated failures (three times in five years) add up: 3 × ($6 + $3.30 labour) = $27.90 — still less than a single G7J-4A at $45. So the MY4 can actually be the lowest TCO if the labour cost is low and you accept the risk of six failures. The reversal: if the downtime cost per event exceeds $200, the MY4 becomes the most expensive. Always propagate the cost of an outage as a constraint.

Topology/standards per the cited standards; all product ratings are manufacturer-stated values from the cited datasheets, current to 2026-06; derived/illustrative figures are labelled as such. This is not an independent head-to-head test. Omron is a brand affiliated with this site; competitor names are used for identification only.