Original research · Code & Safety

What Was Typically Installed, By the Decade Your Home Was Built

Name: US housing stock by construction era, with typical wiring method, grounding practice and governing NEC edition
Creator: HyreElectrical Research Desk
License: https://www.census.gov/data/developers/about/terms-of-service.html

Ten construction eras, mapped to the wiring method, grounding practice and NEC edition that governed new construction in each — built from Census housing data and a named history of residential wiring practice. This is the reference table; for the panel-brand hazard and state ranking, see our companion study below.

Updated September 6, 2026 · Data as of 6 September 2026

Written by HyreElectrical Research Desk Primary-source research and fact checking

1962 NEC edition first required a grounding conductor on every branch circuit in a home

11.9% of US homes built 1939 or earlier, when knob-and-tube wiring was still the default

10.0% of US homes built 1960–1969, the decade universal grounding arrived

10 construction eras measured each mapped to its typical wiring, grounding practice and governing NEC edition

The finding

The year a house was built tells you what it was very likely built with — but not what is in the walls today. Ungrounded, two-prong wiring was the practical default in every home built before the 1962 National Electrical Code, which was the first edition to require a grounding conductor on every branch circuit; that single revision reorganizes this entire page. 16.4% of the current US housing stock — 23,347,227 units — was built before 1950, entirely inside the pre-grounding era. A further narrower window, 1965 to the mid-1970s, saw aluminum branch-circuit wiring installed as ordinary NM cable in response to a copper shortage — a wiring method, distinct from the Federal Pacific and Zinsco panels our companion study measures. None of this identifies a specific home’s current wiring. Homes get rewired and panels get replaced, and no Census table records either. What follows is a reference table for the era a home was originally built in, not a diagnosis of the one you own.

Read this before you use any row of this table

Every figure below describes what a home was very likely built with, in the decade it was built. It says nothing about what is in that home’s walls today. The American Community Survey records the year a structure was built. It records nothing about rewiring, panel replacement, remodeling or partial upgrades, and there is no national dataset that does.

A 1968 house rewired in copper in 2005 is counted identically, in every row below, to one that has never been touched. Construction era is a proxy for original installation, never a measurement of current condition, and that distinction holds at every table, chart and figure on this page — not just here.

Why a build-era table, and how it differs from our panel study

HyreElectrical already publishes a study ranking every state by the share of its housing stock built in the 1950–1989 installation window for Federal Pacific and Zinsco panels. That study answers a geography question — where is the exposed stock concentrated. It does not answer a different, more basic question a reader asks first: for a home of any given age, what wiring method, grounding practice and code requirement was actually typical when it was built? No page on this site had built that reference table. This one does.

HYRE analysis. The two pages are deliberately not the same shape. The panel study ranks states on one measured quantity and tells an insurance and recall story. This page has no ranking and no insurance angle — it is a decade-by-decade map of ordinary wiring practice, built from a national history of residential wiring rather than a panel-brand controversy. A home inspector or a real estate agent explaining an old house to a buyer needs this table, not a state ranking.

The reference table: ten eras, three questions each

All 142,332,876 US housing units by the decade the Census Bureau records them as built. The 1970s is the single largest bracket. US Census Bureau, ACS 2023 5-year estimates, table B25034, retrieved 6 September 2026. Figures reused from this desk’s own hazard-era-electrical-panels study and cross-checked against this site’s knob-and-tube-wiring and grounding-and-bonding guides, all three drawing the same table.

Built	US housing units	% of stock	Wiring method typical of new construction	Grounding practice	Governing NEC edition or Code milestone
1939 or earlier	16,917,912	11.9%	Knob-and-tube — open, individually run conductors on porcelain knobs and tubes — was the dominant method. Armored cable (listed 1903) and nonmetallic (NM) cable (listed 1926) existed but had not displaced it in ordinary houses.	Ungrounded as the practical default. The 1913 Code’s grounding mandate applied only to select circuit types, such as the residential Edison three-wire system — not to general branch circuits or receptacles.	NEC 1903 (recommended grounding on some circuits; first listed armored cable); NEC 1913 (mandatory grounding, narrow scope); NEC 1926 (first listed NM cable).
1940–1949	6,429,315	4.5%	Knob-and-tube was being phased out for armored cable, popular since around 1930, and NM cable — still jacketed in varnish- or tar-impregnated cotton braid rather than plastic.	Still almost entirely ungrounded. The 1947 Code was the first to require a grounding-type (three-prong) receptacle anywhere in a house, and only for the laundry circuit.	NEC 1940 (Type S tamper-resistant plug fuses required for new work, effective 1 Nov 1941); NEC 1947 (laundry-circuit grounding receptacle; also first permitted grounding an electric range’s frame through the service neutral — a narrow allowance, not general branch grounding).
1950–1959	13,784,571	9.7%	NM cable’s cotton-braid jacket began giving way to synthetic spun rayon around 1950. In the panel, low-cost residential circuit breakers — new from Square D and others in the post-war building boom — started displacing the plug fuse in new construction.	The 1953 Code extended the range’s neutral-frame-grounding allowance to electric clothes dryers. The 1956 Code required grounding-type receptacles in basements, garages, outdoor locations and other places a person might be standing on the ground.	NEC 1953 (dryer neutral-grounding allowance); NEC 1956 (grounded receptacles required room by room, still short of universal).
1960–1969	14,254,921	10.0%	By 1960 the circuit breaker had almost completely replaced the fuse in new construction. Early in the decade a thermoplastic jacket began replacing NM cable’s cloth braid. From 1965 a copper shortage brought aluminum branch-circuit wiring, installed as ordinary NM cable — its own section below.	The pivot point of this whole table. The 1962 Code required a grounding conductor or ground path on every branch circuit, which as a practical matter ended the new two-prong, non-grounding receptacle. Most NM cable made before the early 1960s carried no grounding conductor at all; cable made after generally did.	NEC 1962 — universal branch-circuit grounding. The single most consequential edition in this table.
1970–1979	20,484,570	14.4%	Aluminum branch-circuit NM wiring was at its most common through the first half of this decade, then retreated as copper prices fell and the fire-hazard publicity spread. By around 1970 most NM cable carried a PVC outer jacket rather than cloth or rayon braid.	Universal since 1962. One gap got fixed in 1969: earlier grounded NM cable was permitted an undersized grounding conductor for 14-, 12- and 10-gauge circuits; a 1969 change closed that.	NEC 1969 (closed the undersized-ground-conductor allowance); NEC 1971 (strengthened the water-pipe grounding-electrode requirement — it now had to always be supplemented by a driven rod or pipe electrode).
1980–1989	18,543,944	13.0%	Aluminum branch wiring was rare again in new construction; copper NM was standard. A cloth-braid jacket remained permitted until 1984, when NM-B — rated for 90 °C conductors inside a 75 °C jacket — was introduced and began replacing the older 60 °C/75 °C cable.	Unchanged — universal and correctly sized since the 1960s changes above.	NEC 1984 (NM-B cable). Ground-fault-interrupter coverage kept expanding location by location — whirlpools and tubs were added in 1981.
1990–1999	18,211,985	12.8%	Copper NM-B was the uncontested standard branch-circuit cable for ordinary residential work.	The 1993 Code stopped counting interior metal water pipe more than five feet from the building entrance as part of the grounding electrode system, recognising the spread of non-metallic water piping. The 1996 Code ended the old neutral-frame-grounding allowance for a new range or dryer branch circuit — the origin of the modern four-prong range and dryer receptacle.	NEC 1993, NEC 1996 (as above); NEC 1999 (arc-fault circuit interrupters first described in the Code text, not yet required).
2000–2009	19,324,640	13.6%	No wiring-method change of this table’s scale occurred; copper NM-B continued as the default.	The 2002 Code permitted either white or gray insulation to identify a grounded conductor — a labelling clarification, not a change in grounding practice.	NEC 1999/2002 — arc-fault protection became mandatory 1 January 2002 for 15- and 20-ampere branch circuits supplying bedroom receptacles, the first AFCI mandate reaching an ordinary house.
2010–2019	12,736,038	8.9%	Not independently verified for this table. See the note above the table.	Not independently verified for this table. See the note above the table.	This desk’s dated source (Dini, 2006) predates the 2011, 2014 and 2017 editions entirely. What is well documented elsewhere and not in dispute: AFCI and GFCI coverage continued broadening across these editions, and grounded copper NM-B (or conduit, where locally required) remained the uncontested default. No specific edition-by-edition account is asserted here.
2020 or later	1,644,980	1.2%	Too small and too recent a bracket to support an independent finding.	—	Three years of construction inside a five-year survey window. Included for completeness of the total; no era-specific claim is made.

Wiring-method, grounding-practice and Code-milestone columns: David A. Dini, P.E. (Underwriters Laboratories), “Some History of Residential Wiring Practices in the U.S.” (2006), read in full 6 September 2026, plus CPSC Publication 516 (June 2011) for the aluminum-wiring rows. See Sources.

What this table omits on purpose: a dated, decade-by-decade figure for typical new-construction service size (30/60/100/150/200 A). Dini (2006) states only that “the earliest main switches were of a blade type typically rated 30, 60 or 100 A,” without dating that to a specific decade, and no source giving a dated amperage progression through the 1950s–2020s was found in this research. Rather than invent one, this page does not publish it. See Limitations.

Why 1962 is the one date on this table worth memorising

Three separate strands of Code history converge on the same few years. Grounding-type (three-prong) receptacles arrived gradually and by location — laundry circuits in 1947, then basements, garages and outdoor receptacles in 1956. Circuit breakers overtook fuses in new construction by around 1960, a manufacturing-cost story unrelated to the Code. Then the 1962 Code required a grounding conductor on every branch circuit in a house, closing the gap the location-by-location approach had left open.

HYRE analysis. The practical effect is that “built before 1962” and “built with ungrounded, two-prong receptacles as the norm” describe almost the same set of houses. It is not a legal requirement to rewire an older home — non-grounding receptacles remain permitted for replacement use in existing installations that never had a ground path — but it is the single fact a homeowner asking “does my old house have grounded outlets” should reach for before any other on this page.

Six terms this table depends on

Knob-and-tube: The earliest open residential wiring system: single insulated conductors run through air, supported on porcelain knobs and threaded through porcelain tubes. Dominant until the 1930s; not permitted for new work since the mid-1970s, though existing installations may remain (Dini, 2006).
Armored cable (AC / “BX”): A flexible steel-jacketed cable, first listed in 1899 for Sprague Electric under the trade name “Greenfield.” “BX” was originally the experimental variant’s internal code name and became General Electric’s registered trade name after it acquired Sprague. First appeared in the 1903 NEC; did not become common until around 1930 (Dini, 2006).
Nonmetallic cable (NM / “Romex”): Plastic-sheathed cable, first listed and described in the 1926 NEC, invented a few years earlier by General Cable’s Rome Wire Division — “Romex” is a General Cable trade name still used generically today. Most residential NM made before the early 1960s carried no grounding conductor (Dini, 2006).
Grounding conductor: A dedicated conductor that gives a fault current a low-resistance path back to the source, so an overcurrent device trips instead of energising a metal surface. Required on every residential branch circuit since the 1962 NEC.
AFCI (arc-fault circuit interrupter): A breaker that recognises the electrical signature of an arc fault and de-energises the circuit before it can ignite nearby material. First described in the 1999 NEC; mandatory from 1 January 2002 for 15- and 20-ampere bedroom branch circuits (Dini, 2006).
GFCI (ground-fault circuit interrupter): A device that trips on a small current imbalance between hot and neutral, protecting against shock rather than fire. First required by the Code in 1968, for underwater pool lighting; extended location by location through the 1970s–2000s (Dini, 2006).

The narrower window inside the 1960s and 1970s

Aluminum branch-circuit wiring sits inside the 1960–1979 rows above, and it deserves its own short section because it is the one wiring-method change on this page with a federal safety record behind it, not just a UL history. The Consumer Product Safety Commission states plainly: “Homes built before 1965 are unlikely to have aluminum branch circuit wiring. Electrical cables installed between 1965 and the mid 1970s in new homes, in additions, and as part of rewired/new circuits may contain aluminum wiring” — driven by a mid-1960s copper shortage that pushed the metal from large-appliance circuits into ordinary 15- and 20-ampere general-purpose work. Virtually all of it was installed as ordinary NM cable, per CPSC — a wiring method, indistinguishable by cable type from a copper run without reading the jacket markings.

CPSC’s own finding is specific and worth quoting exactly rather than rounding: a national survey for the Commission found homes built before 1972 and wired with aluminum are “55 times more likely to have one or more wire connections at outlets reach ‘Fire Hazard Conditions’ … than homes wired with copper,” a result that covered outlet connections only. This page does not repeat the panel-brand or insurance story that finding feeds into — the aluminum-wiring identification steps, the three CPSC-recognised permanent repairs, and every insurer document are on our companion study and on our aluminum wiring guide. This section exists only to place the aluminum era correctly inside the wider wiring-method timeline.

Fuses to breakers, and the service-size question this page will not invent an answer to

Before the 1930s, the earliest residential service equipment was a blade-type main switch, typically rated 30, 60 or 100 amperes, feeding individual branch fuses often housed in a separate “fuse cabinet.” Westinghouse introduced the first circuit-breaker-based “No-Fuze Load Center” in the 1930s, but at a price that put it out of reach of all but the most expensive houses during the Depression. Low-cost residential breakers did not arrive from other manufacturers until the early 1950s post-war building boom, and by 1960 the breaker had almost completely replaced the fuse as the overcurrent protection of choice in new construction (Dini, 2006).

What we could not verify, and will not guess at: a dated year-by-year figure for when 100-ampere, then 150-ampere, then 200-ampere service became the new-construction norm. The demand-side story is not controversial — central air conditioning, electric ranges, and later EV charging each raised the load a new house was built to carry — but this desk located no primary or citable source that dates that progression by decade, and NFPA’s own site did not return retrievable body content on the retrieval date (see Method). Per this network’s standing rule, the honest gap is disclosed rather than filled with an invented boundary year. A currently-adequate service size is a question our load calculator and a licensed electrician answer for a specific house — not this table.

Limitations

Construction era is a proxy for original installation, never for current condition
Repeated because it is the limitation that matters more than the rest combined. No row in this table, and no figure derived from it, describes a specific home’s wiring today.
Typical new-construction service size (30/60/100/150/200 A) is not dated by decade
The one service-size fact this page could verify — “blade-type mains, typically 30, 60 or 100 A” — is not itself dated to a specific decade in the source. No later-era figure is published because none could be sourced. See the overcurrent-protection section above.
The wiring-method and grounding-practice narrative rests on one named history, cross-checked against CPSC for aluminum only
Dini (2006) is a professional (UL) publication, not a government primary source, and it is the single document behind most of the wiring-method and grounding-practice columns. Where CPSC’s own aluminum-wiring publication overlaps it, the two agree; the rest of the narrative was not independently cross-verified against a second source in this research.
NFPA 70 itself is cited by edition and provision, never quoted
NFPA 70 is copyrighted, and its own site did not return retrievable body text for direct quotation on the retrieval date (see Method). Every Code-edition date in this table is sourced to Dini (2006) or CPSC Publication 516 describing what a given edition required, not to the Code text itself.
This table does not cover 2011 through 2026 NEC editions with named specificity
Dini (2006) predates every edition after 2008. The 2010–2019 and 2020-or-later rows say this openly rather than borrowing an earlier edition’s level of detail for years this research did not verify.
Five-year ACS estimates are a five-year average, and the newest bracket is very small
ACS 2023 5-year data pools 2019 through 2023. The “2020 or later” bracket represents at most three or four years of construction inside that window and is too small a sample to support any independent finding — it is published only for the total to add correctly.
Mobile homes are dated by model year, not construction technique
Census dates mobile homes, houseboats and RVs by the manufacturer’s model year. Their electrical systems follow the HUD manufactured-home code, a different regulatory track from the site-built NEC history this table describes, and are not separated out here.

Method

Housing-stock source. US Census Bureau, American Community Survey 2023 5-year estimates, table B25034 (Year Structure Built), United States total. These are the same national figures already retrieved and published for hazard-era-electrical-panels.js and reused, not re-derived, on this site’s knob-and-tube-wiring and grounding-and-bonding guides — reused again here so all four pages agree to the unit.

Wiring-method and grounding-practice source. David A. Dini, P.E., Underwriters Laboratories Inc., “Some History of Residential Wiring Practices in the U.S.” (Copyright 2006), read in full — all 17 pages — on 6 September 2026. Every dated claim in the wiring, grounding and code-milestone columns not attributed to CPSC is drawn from this document.

Aluminum-wiring source. US Consumer Product Safety Commission, Publication 516, “Repairing Aluminum Wiring” (June 2011), re-read on 6 September 2026 from CPSC’s own hosted PDF. The same document already cited on ELE-08 and on this site’s aluminum-wiring guide, reused here rather than re-found, per this network’s standing instruction to reuse a source once verified.

NFPA 70 retrieval. NFPA 70 is copyrighted, so no Code text is quoted anywhere on this page — every Code-edition reference describes what Dini (2006) or CPSC report an edition requiring. On the retrieval date, repeated attempts to retrieve NFPA’s own edition-history and product pages returned either an HTTP 404 or a page whose body content is rendered client-side and was not retrievable as text; this matches the standing note already recorded on this site’s /tools/nec-edition-lookup/ tool, which documents the identical failure for state-adoption data. NFPA 70 is cited below by its standard-development URL for the record, with that limitation disclosed rather than worked around by quoting a secondary source as if it were NFPA’s own text.

What was deliberately left out. A dated, decade-by-decade typical service-size figure (see the overcurrent-protection section) and any independent account of NEC editions after 2008 (see the 2010s and 2020s table rows) — both because no citable source was found, not because the questions are unimportant.

Reproducibility. The housing-unit counts are a single public Census table. The wiring, grounding and code narrative is drawn from two named, dated, publicly available documents, both cited in full below with the pages and passages relied on. Anyone with the same two documents and the same Census table can check every row.

Questions

When did homes start getting grounded electrical outlets?

In stages, not all at once. The 1947 NEC first required a grounding-type (three-prong) receptacle, but only for the laundry circuit. The 1956 Code extended that to basements, garages and outdoor locations. The 1962 Code was the one that mattered most: it required a grounding conductor on every branch circuit in a house, which as a practical matter ended new installation of the ungrounded, two-prong receptacle.

Is a house built before 1962 automatically ungrounded?

Not automatically — it means ungrounded, two-prong receptacles were the practical default when it was built, not that the home has never been touched since. Many pre-1962 homes have been partially or fully rewired in the decades since, and nothing in Census data records that. The only way to know a specific home’s current wiring is to have it inspected.

What is the difference between this page and HyreElectrical’s hazard-era panel study?

Our companion study, hazard-era-electrical-panels, ranks every state by the share of its housing built in the 1950–1989 window associated with Federal Pacific and Zinsco panels, and covers the insurance and recall story around those two brands. This page does not rank states or discuss panel brands — it is a national, decade-by-decade reference table for the wiring method, grounding practice and Code edition typical of new construction in each era.

Which years did homes commonly get aluminum wiring?

The Consumer Product Safety Commission states homes built before 1965 are unlikely to have aluminum branch-circuit wiring, and that cables installed between 1965 and the mid-1970s — in new homes, additions, or rewired circuits — may contain it. A mid-1960s copper shortage drove the shift. Virtually all of it was installed as ordinary NM (Romex-type) cable, not as a visually distinct product.

What kind of wiring did houses have before the 1940s?

Knob-and-tube: individual insulated conductors run through open air, supported on porcelain knobs where they crossed framing and threaded through porcelain tubes where they passed through it. It was the dominant residential method until it began being phased out in the 1930s in favor of armored and nonmetallic cable. It has not been permitted for new installations since the mid-1970s, though existing knob-and-tube wiring is not automatically illegal.

When did residential circuit breakers replace fuse boxes?

Circuit breakers existed from the 1930s (Westinghouse’s “No-Fuze Load Center”) but cost more than most Depression-era buyers would pay, so nearly all but the most expensive houses kept fuses. Low-cost residential breakers arrived from other manufacturers in the early 1950s post-war housing boom, and by 1960 breakers had almost completely replaced fuses as the choice for new construction.

Does this page tell me what size electrical service my house needs?

No, and it says so deliberately rather than guessing. This page could verify only one dated fact about historical service sizing — that the earliest main switches were typically rated 30, 60 or 100 amperes — with no sourced decade-by-decade progression after that. A currently adequate service size for a specific house is a job for a load calculation and a licensed electrician, not a construction-era table.

If my home is in the pre-1962 or aluminum-wiring window, do I need to do anything?

This page identifies eras, not individual homes, and does not recommend action for a house it has never seen. If you want to know what your specific home has, the safe first step is to read what the panel and visible cable jackets already show you — never to open a live panel yourself — and involve a licensed electrician for anything beyond that. See our companion research for the identification steps.

Written and audited by

HyreElectrical Research Desk

Primary-source research and fact checking

We read the model code, the federal safety notice, the municipal fee sheet or the utility tariff ourselves, and we publish the figure with the document it came from and the date we retrieved it. Where a number cannot be traced to a primary source, we publish the shorter page and say what we could not verify. HyreElectrical does not perform, supervise or warrant electrical work. Authorship is organisational: this desk, not a named persona.

10: long-form launch pages in this layout
5: states with verified licence records
16,369: electrical companies in those records
74%: of the store is Florida — disclosed first, not footnoted

How this desk works

Primary sources only. Code statements come from NFPA 70 as the model code. Safety statements come from CPSC. Permit fees come from the city or county fee sheet. Utility charges come from the filed tariff. We do not cite a blog that cites a source; we open the source.
Our contractor store is five states, and 74% of it is Florida. Any figure built on that store is titled to those states and names the concentration in the first screen. It is not a national sample of electricians.
Load calculations on this site are a published simplification in the shape of NEC 220.82 — first 10 kVA at 100%, remainder at 40%, HVAC at 100%, EVSE at 125%. They are labelled as not a stamped calculation. A licensed electrician using the adopted edition does that work.
No national price for a panel upgrade is shipped. Labour rates, the adopted code edition, whether the utility is involved, and the state of the existing wiring move the invoice too far for a roundup to help. Cost intent lives on the cost page; this page explains the decision.
We do not perform electrical work, and we take no payment for placement, ranking or a favourable mention. Nobody buys a position on this site.

Data as of 6 September 2026. Authorship on this site is organisational: the analysis belongs to the desk rather than to a named individual, and we do not publish credentials we do not hold. Our editorial policy sets out how we source, date and correct what we publish.

The data behind this page

Every figure on this page is computed from one file, and that file is published here so the analysis can be checked, disagreed with, or reused.

Download the dataset (CSV)

Sources & retrieval dates

US Census Bureau — American Community Survey 2023 5-year estimates, table B25034 (Year Structure Built) , United States total: 142,332,876 housing units across ten construction-era brackets. Reused from this desk’s own hazard-era-electrical-panels.js and cross-checked against the same table already cited on this site’s knob-and-tube-wiring and grounding-and-bonding guides. Retrieved 6 September 2026.
David A. Dini, P.E., Underwriters Laboratories Inc. — "Some History of Residential Wiring Practices in the U.S." (2006) , Read in full, all 17 pages. Source of the knob-and-tube phase-out dating, armored-cable and NM-cable listing and adoption history, the 1913/1933/1940/1947/1953/1956/1962/1969/1971/1993/1996/1999/2002 Code-revision dates quoted or paraphrased above, and the fuse-to-breaker overcurrent-protection history. Retrieved 6 September 2026.
US Consumer Product Safety Commission — Publication 516, "Repairing Aluminum Wiring" (June 2011) , Source of the 1965-to-mid-1970s aluminum branch-wiring installation window, the mid-1960s copper-shortage driver, the statement that virtually all aluminum branch wiring was installed as NM cable, and the 55-times Franklin Research Institute fire-hazard finding for pre-1972 aluminum-wired homes at outlet connections. Retrieved 6 September 2026.
National Fire Protection Association — NFPA 70, National Electrical Code , Cited by edition year and provision, never quoted: NFPA 70 is copyrighted, and repeated attempts to retrieve NFPA’s own edition-history and product pages as readable text failed on the retrieval date (HTTP 404, or client-side-rendered content with no retrievable body text) — the same failure already documented on this site’s /tools/nec-edition-lookup/ tool for state-adoption data. Every Code-edition date above is sourced to Dini (2006) or CPSC 516 describing what an edition required, not to NFPA’s text. Retrieved 6 September 2026.

Know your home’s build era — not sure what that means for your wiring?

The build-era table describes the era, not your specific house. If you want to know what you actually have, the next step is a licensed electrician who will look at the panel and the cable jackets, not a guess from a Census bracket.

Panel upgrades explained Check your load first

HyreElectrical does not perform, supervise or warrant electrical work, and takes no payment for placement, ranking or favourable mention. This page describes construction-era norms, not any specific property, and nothing on it substitutes for an inspection by a licensed electrician. We have no commercial relationship with Underwriters Laboratories, the Consumer Product Safety Commission or the National Fire Protection Association.