North American EMS posted a book-to-bill ratio of 1.36 in April 2026, with total shipments up 3.1% versus the same month a year earlier [S1]. The reading is well above the 1.0 parity line that separates backlog growth from contraction, and it sits inside a multi-month stretch of order intake running ahead of billed output [S1].
Capital-goods sub-segments that overlap with electrical equipment are running even hotter: a 40-segment tracker covering operating segments from ABB, Siemens Energy, GE Vernova, Vertiv, Trane, and Emerson showed an aggregate book-to-bill of 1.3x in the trailing twelve months ended June 2026, the highest level in the past decade [S5]. Four of seven sub-indices in that file, including aviation, gas turbines, HVAC, and power electronics, were above 1.5x simultaneously, a configuration the tracker flagged as unusual [S5].
What the 1.36 EMS reading actually means
EMS book-to-bill divides the dollar value of new orders booked by the dollar value of units shipped and billed over the same period; 1.36 means $136 of orders entered the backlog for every $100 invoiced [S1][S3]. A sustained reading above 1.0 indicates that contract manufacturers are filling backlogs faster than they are burning them down, which historically translates into lead-time pressure on passive components, bare PCBs, and contract assembly capacity [S1].
IPC, the trade body that publishes the monthly North American EMS report, has flagged the figure as evidence of demand running ahead of supply on the assembly side, with shipments still growing year-over-year despite a tightening capacity environment [S1]. For buyers of finished electronics assemblies and for OEMs sourcing populated boards, the practical signal is to lock in slot allocation with EMS partners earlier in the design cycle, since the historical two-to-three-month booking window is contracting [S1].
Where the data is, and where it stopped
The most-quoted semiconductor equipment book-to-bill series, the SEMI North America report, was discontinued in 2017, and SEMI now publishes a billings report without the ratio [S4][S7]. The archive on Economy.com and macromicro both label the series discontinued, with the final maintained entries showing order and shipment values through late 2017 and only shipment values thereafter [S2][S7].
For live signal in 2026, the two most-cited live series are the IPC North American EMS report and the SEMI Worldwide Semiconductor Equipment Billings report (dollar value only, no ratio) [S1][S4]. Investors and procurement teams that still need a ratio for the front-end equipment side have to back-calculate from the published dollar figures, since SEMI no longer releases the ratio itself [S4][S7]. The historical peak context is still useful: the North American semiconductor equipment ratio hit 1.41 in early 2000, a level that, in nominal terms, the EMS series has now matched or exceeded in the past year [S9].
Power electronics, HVAC, and gas turbines inside the capital-goods tracker
Power electronics book-to-bill averaged 1.06x from 2015 to 2021, then stepped up and has consistently run at 1.5x through the latest quarterly data in early 2026, the longest stretch of high book-to-bill ratios for any sub-segment in the 40-segment file [S5]. That sub-segment draws operating-segment data from ABB, Siemens Energy, GE Vernova, and Vertiv, and is being driven by grid-tied inverters, MV drives, and data-center power distribution equipment [S5].
Gas turbines were the standout at 2.67x in Q2 2026, remaining above 1.9x for three straight quarters, the strongest stretch in the data series [S5]. HVAC read 1.7x in the past year, with the tracker linking the move to data-center build-out and the rise of liquid-cooled compute halls [S5]. The combined signal across these three sub-segments is consistent with the EMS 1.36 reading: electrical equipment, power conversion, and the cooling and prime-power feeding it are all running above parity simultaneously, a configuration the tracker notes has occurred in only five prior episodes in the past decade, with an average two-year duration before reversion [S5].
How to read the ratio when a sub-segment is missing
Not every electrical equipment sub-segment has a clean public ratio. For categories like switchgear, transformers, and UPS units, the practical substitution is to back-calculate from backlog disclosures and segment revenue, since large OEMs in the electrical automation and electrical measurement spaces report both figures in their quarterly results, even when they do not label the ratio [S5].
For lighting, lighting equipment and electric lamps procurement teams are seeing a similar signal through lead-time extension rather than a published ratio: outdoor LED fixture and high-bay industrial luminaire lead times have moved from stock-plus-one-week to eight-to-twelve-week in the same window where HVAC and power electronics are running above 1.5x [S5]. The capital-goods tracker also covers only 40 sub-segments, and heavy electrical equipment such as large transformers and HV breakers is not in the file; for those, OEM backlog disclosures remain the only live signal [S5].
Selection criteria: when to trust the ratio, and when not to
Use the ratio when the data series is reported by a trade body (IPC, SEMI) with consistent methodology and three-month smoothing, and when backlog and revenue are sourced from operating-segment disclosures that are GAAP-comparable quarter-to-quarter [S3][S5]. Treat the ratio as a directional indicator rather than a forecast: a book-to-bill ratio of 1.36, as reported for North American EMS in April [S1], means orders were running 36% ahead of billings that month rather than representing a 36% backlog growth rate [S3].
Avoid comparing ratios across sub-segments without normalizing for the 10-year base: the capital-goods tracker notes the 10-year average is 1.09x across all 40 segments, so a 1.3x aggregate is genuinely elevated, but a 1.5x in wind industry, where the long-run mean is lower, is a different signal than 1.5x in power electronics, where the long-run mean is 1.06x [S5]. For equipment selection in construction machinery and equipment categories not covered by the tracker, a single-vendor backlog disclosure is a weaker signal than an industry-aggregate ratio, since one large order can swing the segment number [S5].
Adjacent demand signals worth tracking
Two adjacent data points reinforce the same direction. The 2026 Edge AI server demand picture, with embedded inference pushing more power and cooling per rack, is a direct read on the power-electronics and HVAC ratios covered above. For mechanical-electrical contractors scoping construction machinery and equipment packages, a rental-cost ladder tied to the same AI build-out is the other half of the demand signal. [S5]
The DC fast charger lead-time tracker shows stock 2-week chargers running out faster than custom 4-week units in 2026, consistent with power-electronics 1.5x and HVAC 1.7x, and giving a separate procurement-side confirmation of the order-intake story. Watch the IPC monthly release for the next EMS print after April 2026, and the next quarterly update to the 40-segment capital-goods file: either ratio dropping back below 1.0x for two consecutive periods would be the first hard reversion signal against the current two-year run.