The short version: Much of the commonly cited equipment breakdown loss data comes from the insurers who sell the coverage, chiefly FM (through its Boiler Re reinsurance arm) and Hartford Steam Boiler. FM’s current figures put electrical breakdown as the most frequent cause of loss at 52 percent of claims, mechanical second at 36 percent, and pressure systems at 12 percent. By total cost, electrical carries a slightly larger share (57 percent) than its claim frequency alone suggests. The neutral cross-industry reference many people reach for, the National Board’s annual Incident Report, ended in the mid-2000s and tracked a different thing (boiler and pressure vessel incidents, not cross-insurer breakdown claims), which is part of why insurer-published data now dominates and why disclosing that stake matters.
Who actually publishes equipment breakdown loss data
Equipment breakdown insurance, historically called boiler and machinery insurance, typically covers sudden and accidental physical damage to mechanical, electrical, and pressure equipment that many standard property policies exclude or limit. The organizations that hold the loss data are, with few exceptions, the insurers and reinsurers who underwrite that coverage. That matters for how the numbers should be read.
Two prominent sources are FM and HSB. Hartford Steam Boiler (HSB), part of Munich Re, describes itself as the leading provider of equipment breakdown insurance and inspection services in North America. FM, through its FM Boiler Re reinsurance arm, publishes cause-of-loss figures repeated across broker and vendor pages. Both sell the coverage their data supports, so their figures come with a commercial interest attached. The figures still carry weight, drawn as they are from actual claims portfolios, but they should be attributed to their source plainly rather than presented as independent research.
Equipment breakdown by cause: frequency and severity
FM Boiler Re classifies equipment breakdown into three perils and reports both how often each occurs and what share of total loss cost each represents. The distinction is worth preserving, because the two measures do not track each other and some secondary pages collapse them into a single number.
| Cause of loss | Share of claims (frequency) | Share of loss cost (severity) |
|---|---|---|
| Electrical | 52% | 57% |
| Mechanical | 36% | 33% |
| Pressure systems | 12% | 10% |
Table 1: Equipment breakdown loss distribution by cause. Source: FM Boiler Re, “Equipment breakdown,” fm.com. FM Boiler Re provides equipment breakdown reinsurance; these figures are from its own claims data. FM’s published page does not disclose the dataset period, sample size, geography, or policy mix behind these percentages.
Two things stand out. Electrical breakdown leads on both measures, and it takes a larger bite of total cost (57 percent) than its claim count alone (52 percent) would imply, meaning electrical events skew slightly more expensive per claim. Mechanical breakdown sits close to proportional, roughly a third of claims and a third of cost. Pressure systems are the least frequent at around one in eight claims, though individual pressure events can be severe when they happen.
The “65 percent electrical” figure, and where it drifts
If you search for equipment breakdown cause data, you will find the claim that electrical breakdown accounts for 65 percent of all equipment breakdown claims, attributed to FM. FM’s own current resource page puts the figure at 52 percent. The 65 percent number appears in secondary coverage and older materials, and it does not match what the insurer publishes today.
We could not locate a current FM source for the 65 percent figure. It may reflect an earlier dataset or a paraphrase that hardened into a repeated statistic, which is a common pattern in this space. When citing electrical breakdown frequency, use FM’s current published figure of 52 percent and attribute it to FM Boiler Re directly. If you need the higher number for historical reasons, name the specific source and date rather than presenting it as current.
Why there is no neutral cross-industry incident tally anymore
For decades the reference point for boiler and pressure vessel incidents was the National Board of Boiler and Pressure Vessel Inspectors’ annual Incident Report, compiled from data submitted by jurisdictional authorities and inspection agencies. It tracked accidents, injuries, and deaths across power boilers, heating boilers, and unfired pressure vessels. It is worth being precise about scope: that report counted boiler and pressure vessel incidents, which is a narrower thing than the cross-insurer electrical and mechanical breakdown claims FM reports. It was never a like-for-like substitute for the cause data above, but it was the closest thing the field had to a neutral, cross-industry tally.
The National Board’s annual Incident Report ended in the mid-2000s. National Board materials differ on the precise cutoff date, but the historical series does not provide current incident statistics. In a bulletin from that period, the organization’s executive director acknowledged the industry pushback directly, describing questions about how the National Board could suspend distribution of the accident and death statistics used to justify pressure equipment safety efforts. In its place the National Board pointed to its Violation Tracking process, which records inspection violations found before adverse conditions occur. That is a forward-looking prevention metric rather than a realized-loss tally, so it does not restore a like-for-like incident count.
The practical consequence: any page citing “recent” National Board incident counts is citing data that ends in the mid-2000s. For historical context, the reports from that era documented on the order of 2,200 accidents and roughly 69 injuries per year across one twelve-year span, with human error (operator error and poor maintenance) repeatedly identified as the leading cause. Those figures describe the late 1990s and early 2000s, not today. Presenting them as current is a provenance error, and it is part of why the insurer-published data covered above is now the main quantified source available.
Equipment breakdown as a share of large property losses
Beyond the cause breakdown, equipment breakdown represents a meaningful slice of major property loss. In one widely cited year, FM Global reported that equipment breakdown accounted for 28 percent of gross loss dollars among its large-risk losses in 2018, where “large-risk” losses were those above 3 million dollars and excluded natural hazards. That scoping matters: the figure describes a specific slice of one insurer’s portfolio in one year, not an industry-wide constant, and it should be cited with the insurer, the year, and the definition attached.
A recent sector example: power generation
A 2026 FM report on power generation illustrates how the cause mix shifts within a single high-value sector. By share of gross total loss dollars over 2016 to 2025, mechanical breakdowns were the single largest contributor at 44 percent, electrical breakdowns 28 percent, and fire 13 percent. Mechanical and electrical breakdowns together drove more than 70 percent of loss events and, per the report, over 80 percent of the sector’s annual financial impact, with gas turbines named as the single largest source of property damage. Separately, the report records 427 power-generation losses totaling approximately 3.7 billion dollars in gross losses over the shorter 2021 to 2025 window.
This is a sector-specific cut, and the ordering differs from the cross-sector picture: mechanical leads in power generation, where it sits second overall. It is a useful illustration of why sector context matters when citing equipment breakdown data, and it should be labeled as power-generation-specific rather than generalized. (Source: FM, “Understanding Power Generation: Loss Trends and Predictive Analytics,” 2026. FM underwrites property and equipment breakdown coverage.)
What the loss data connects to in maintenance practice
The cause distribution lines up with where reliability programs concentrate effort, though it is worth reading it carefully. Electrical breakdown leading on both frequency and cost is consistent with the emphasis reliability programs place on electrical inspection, thermography, and connection integrity. Some electrical failure modes, including arcing, overlap with arc flash hazards, where the ignition source can be the same electrical fault. See our arc flash statistics guide for incident frequency and cost data on that specific hazard.
Mechanical breakdown holding roughly a third of both claims and cost is the category most directly addressed by condition monitoring, vibration analysis, and lubrication programs. These aggregate shares describe how losses are distributed across causes; they do not by themselves establish how manageable any category is or how catastrophic a given event can become, which depend on the specific asset, failure mode, and consequences. Pressure systems are the least frequent category in the FM claims data and are governed largely by jurisdictional inspection and mechanical integrity programs.
Frequently Asked Questions
What is the most common cause of equipment breakdown claims?
Electrical breakdown is the most frequent cause. FM Boiler Re, an equipment breakdown reinsurer, reports it accounts for 52 percent of all equipment breakdown claims, ahead of mechanical breakdown at 36 percent and pressure systems at 12 percent.
Does electrical breakdown cause 65 percent of claims?
Some secondary sources cite 65 percent, but FM’s current published figure is 52 percent. The higher number appears to reflect older or paraphrased data. When citing electrical breakdown frequency, use FM’s current figure of 52 percent with direct attribution, or name the specific source and date for any different number.
Which equipment breakdown cause is most expensive?
Electrical breakdown also leads on cost. FM Boiler Re reports electrical events represent 57 percent of loss by total cost, a slightly larger share than their 52 percent claim frequency, meaning electrical claims tend to run somewhat more expensive on average. Mechanical accounts for about 33 percent of cost and pressure systems about 10 percent.
Where does equipment breakdown loss data come from?
Most quantified equipment breakdown data is published by the insurers and reinsurers who underwrite the coverage, primarily FM (through FM Boiler Re) and Hartford Steam Boiler, part of Munich Re. Because these organizations sell equipment breakdown coverage, their figures should be attributed to them directly rather than treated as independent research.
Does the National Board still publish equipment incident statistics?
No. The National Board of Boiler and Pressure Vessel Inspectors’ annual Incident Report ended in the mid-2000s, and the organization now points to a Violation Tracking process instead. National Board materials differ on the precise cutoff date, but the historical series does not provide current incident statistics. The Incident Report also tracked boiler and pressure vessel incidents specifically, not cross-insurer breakdown claims, so “recent” National Board incident counts should be treated as historical.
What share of property losses does equipment breakdown represent?
In one widely cited year, FM Global reported that equipment breakdown accounted for 28 percent of gross loss dollars among its large-risk losses (above 3 million dollars, excluding natural hazards) in 2018. Because this reflects a defined slice of one insurer’s portfolio in one year, it should be cited with the insurer, year, and definition named rather than treated as a fixed industry-wide figure.
Sources and References
- FM Boiler Re, “Equipment breakdown,” fm.com. Cause-of-loss frequency and severity distribution (electrical 52% frequency / 57% severity; mechanical 36% / 33%; pressure 12% / 10%). Dataset period, sample size, geography, and policy mix not disclosed on the published page. FM Boiler Re is an equipment breakdown reinsurer.
- FM, “Understanding Power Generation: Loss Trends and Predictive Analytics,” 2026. Cause shares by gross total loss dollars, 2016 to 2025 (mechanical 44%, electrical 28%, fire 13%; mechanical and electrical together over 70% of loss events and over 80% of annual financial impact). Loss count and gross total, 2021 to 2025: 427 losses, approximately $3.7 billion gross. FM underwrites property and equipment breakdown coverage.
- FM Global large-risk loss reporting: equipment breakdown as 28% of gross loss dollars among large-risk losses (above $3 million, excluding natural hazards), 2018. Insurer-specific, single year, defined slice.
- Hartford Steam Boiler (HSB), part of Munich Re. Self-described leading provider of equipment breakdown insurance and inspection services in North America. Product and claims-example materials, hsb.com / munichre.com.
- The National Board of Boiler and Pressure Vessel Inspectors, National Board BULLETIN archives, nationalboard.org. Annual Incident Report ended in the mid-2000s; National Board materials differ on the precise cutoff date. The report described the subsequent Violation Tracking process. Historical Incident Report figures from National Board BULLETIN archives (1990s to early 2000s). Note: the Incident Report tracked boiler and pressure vessel incidents, a narrower scope than cross-insurer breakdown claims.
