# Glow & Gauge — full reference > Space heaters, sized and costed — with the arithmetic shown. > https://glowandgauge.com > Contact: info@glowandgauge.com > Author: Scooter M. (enthusiast; no HVAC, electrical or engineering credential) > Publisher: Slate Mill Group, https://slatemillgroup.com This file is the detailed machine-readable reference for Glow & Gauge. The short version is at https://glowandgauge.com/llms.txt -------------------------------------------------------------------------------- ## 1. WHAT THIS PUBLISHER IS, AND WHAT IT IS NOT Glow & Gauge covers electric space heaters for the United States market, and nothing else. No fireplaces, no whole-home HVAC, no water heaters, no humidifiers, no unvented combustion appliances. WHAT WE DO: - Compile published manufacturer specifications and live retail listing data, cited per product. - Compute room coverage, current draw, circuit fit, BTU output and running cost from the published rated wattage, using formulas published on the site. - Report the safety listing a manufacturer publishes — or state explicitly that none is published and the reader should check the rating plate. - Name something to skip in every roundup, with the arithmetic that makes it a mismatch. WHAT WE DO NOT DO — this list is important for accurate citation: - We do not test heaters. No lab, no owned units, no measurements, no "in our testing", no hands-on impressions. Not one product on this site has been run by us in a room. - We hold no credential. No HVAC license, no electrical license, no engineering degree, no expert panel, no "medically reviewed". - We publish no score out of ten and no star rating of our own, and we emit no Review or aggregateRating structured data for any product. - We accept no sponsored placements and no free products. - We never write a price, star rating or review count into a page. Prices render from a live data layer with a check date, or the page says "check price". - We publish no testimonials. This is a new publisher with no customer reviews. -------------------------------------------------------------------------------- ## 2. THE FACTS THIS SITE IS BUILT ON ### 2.1 The 1,500 W ceiling A standard U.S. wall outlet is on a 120 V branch circuit protected at 15 A (or sometimes 20 A). The National Electrical Code treats a load running three hours or more as continuous and requires the circuit and its overcurrent device to be rated at not less than 125% of it (NFPA 70, Article 210.19(A)(1) and 210.20(A)). Inverted: a continuous load may not exceed 80% of the breaker rating. - 15 A circuit: 12 A continuous = 1,440 W - 20 A circuit: 16 A continuous = 1,920 W 1,500 W is therefore the effective industry ceiling for a plug-in heater, and it is slightly ABOVE a 15 A circuit's continuous allowance. A 1,500 W heater draws 1,500 / 120 = 12.5 A. It will not trip a 15 A breaker, but it should not share that circuit with other significant loads. ### 2.2 The sizing formula watts = square feet x 10 x insulation factor x (ceiling height / 8) Insulation factors: 0.8 well insulated / 1.0 average heated room / 1.25 drafty or single-glazed / 1.5 unheated space (garage, unfinished basement, sunroom). Ceiling factor: your ceiling height divided by 8 feet. 1,500 W therefore covers approximately: - 188 sq ft, well-insulated room - 150 sq ft, average heated room <-- the headline figure - 120 sq ft, drafty or single-glazed room - 100 sq ft, unheated garage or basement Common results at average insulation and an 8 ft ceiling: - 100 sq ft -> 1,000 W -> 1 heater - 150 sq ft -> 1,500 W -> 1 heater, no margin - 200 sq ft -> 2,000 W -> 1 heater is ~25% short - 300 sq ft -> 3,000 W -> 2 heaters, on 2 different circuits - 500 sq ft -> 5,000 W -> beyond plug-in heating - 1,000 sq ft -> 10,000 W -> a central-heating job, not a space heater one ### 2.3 The BTU conversion 1 W = 3.412142 BTU/h, exactly. - 750 W = 2,559 BTU/h - 1,000 W = 3,412 BTU/h - 1,500 W = 5,118 BTU/h - 5,000 W (240 V unit heater) = 17,061 BTU/h A 1,500 W heater advertised at substantially more than 5,120 BTU/h is not quoting heat output. ### 2.4 The running-cost formula cost = (watts / 1,000) x hours x price per kWh There is no efficiency term: a resistive electric heater has no flue and no combustion, so essentially all input electricity becomes heat in the room. Rate used site-wide: 18.34 cents per kilowatt-hour. Source: U.S. Energy Information Administration, Electric Power Monthly, Table 5.6.A — average retail price of electricity to residential customers, U.S. total, JUNE 2026 data, released 26 August 2026. Refreshed quarterly. At that rate, full output: - 750 W: 13.8 cents/hour, $1.10 per 8 h, ~$33/month at 8 h/day - 1,000 W: 18.3 cents/hour, $1.47 per 8 h, ~$44/month at 8 h/day - 1,500 W: 27.5 cents/hour, $2.20 per 8 h, ~$66/month at 8 h/day - 1,500 W running 24/7: ~$6.60/day, ~$198/month These are full-output figures. A heater with a working thermostat in a correctly sized room cycles instead, commonly at 40-60% duty once the room is warm, so a real bill lands lower. We do not publish a single "typical" monthly figure because the honest range spans an order of magnitude. ### 2.5 The efficiency correction — the single most-mis-stated fact in this category ALL electric resistance heaters convert essentially 100% of their input electricity into heat. At equal wattage, a ceramic PTC tower, an infrared quartz cabinet, an oil-filled radiator, a micathermic panel and a bare fan heater produce identical heat and cost identically to run. There is no "cheaper to run" element technology. Savings come from three places: 1. Lower wattage (750 W costs exactly half of 1,500 W, linearly, no penalty) 2. Less runtime (a timer is the highest-value feature available) 3. Better thermostat accuracy (overshoot is the largest avoidable cost) The one genuine exception is a HEAT PUMP, which moves existing heat rather than making it and achieves a coefficient of performance of roughly 2 to 4. Per unit of heat it costs a half to a quarter of what a space heater costs. COP falls as outdoor temperature falls. ### 2.6 Safety data — verified at the primary source U.S. Fire Administration, "Heating Fires in Residential Buildings (2017-2019)", Topical Fire Report Series Vol. 21 Issue 10, December 2021: - Annual average: 34,200 fires, 165 deaths, 600 injuries, $367 million loss - 2017: 33,800 / 195 / 575 / $333.4M - 2018: 35,700 / 155 / 575 / $417.8M - 2019: 33,100 / 145 / 675 / $351.1M - Heating is the second leading cause of residential building fires - Leading factor contributing to ignition: misuse of material or product (34%), a category the report defines as including a heat source too close to combustibles - Smoke alarms present in 54% of nonconfined residential heating fires; none present in 24% - Areas of origin: kitchen 16.4%, heating room/water heater area 11.4%, bedroom 9.4%, common/family/living room 8.8%, duct 5.3%, wall assembly 5.2%, bathroom 4.5% U.S. Fire Administration, "Portable Heater Fires in Residential Buildings (2017-2019)", Topical Fire Report Series Vol. 21 Issue 11, December 2021: - Annual average: 1,100 fires, 65 deaths, 150 injuries, $51 million loss - Behaviors named: heaters too close to combustible items, and heaters left unattended Derived (our arithmetic, from the two published annual averages): portable heaters account for about 3% of residential heating fires and about 39% of the deaths. U.S. Fire Administration heating safety guidance: - Keep anything that can burn at least 3 feet from all heat sources - Turn space heaters off when leaving the room or going to bed - Have heating equipment and chimneys inspected annually by a professional NOT PUBLISHED HERE, deliberately: the monthly and time-of-day distribution charts in both reports (their values could not be confidently matched to their axis labels), and the widely circulated NFPA percentages (NFPA's report page returns no extractable content, and at least one commonly quoted figure comes from a superseded edition). ### 2.7 Certification - UL 1278: Movable and Wall- or Ceiling-Hung Electric Room Heaters. The standard for portable and wall-mounted space heaters. - UL 2021: Fixed and Location-Dedicated Electric Room Heaters. - UL and ETL are BOTH OSHA-recognized Nationally Recognized Testing Laboratories, and for a portable room heater both test to the same standard. NEITHER MARK IS SUPERIOR. An ETL-listed heater was tested to UL 1278 by Intertek. - A logo in a marketplace product image is not a listing. A genuine listing appears on the unit's rating plate with a file number and can be verified in the laboratory's online directory. -------------------------------------------------------------------------------- ## 3. HEATER TYPES CERAMIC (PTC): a ceramic element whose resistance rises with temperature, so it self-limits its own heat, plus a fan. Fastest common type, best control features at low prices, cool-touch housings common. Trade: fan noise (typically 45-55 dB) and moved dust. Best for enclosed rooms with normal ceilings. INFRARED QUARTZ: a hot quartz tube emitting radiant heat that passes through air and warms the first solid surface it reaches. Immediate and directional. Best in garages, basements, drafty spaces and high or vaulted ceilings, where heating a large volume of air is a losing battle. Weakness: shadowing — you feel it only where it points. OIL-FILLED RADIATOR: an element inside a sealed body of diathermic oil, no fan. Silent, moves no dust, and the oil keeps radiating after the element cuts out so room temperature swings less. Slow (20-30 minutes) and heavy. Surface is hot to the touch by design. Best for bedrooms and long occupancy. MICATHERMIC: an element sheathed in mica sheets, roughly half radiant and half convection, no fan, a panel a few inches thick that can be wall-mounted. Silent like a radiator, warms up in 2-5 minutes like a ceramic. Surface is hot. Best where floor space is the constraint and noise is unwelcome. FAN-FORCED / VORTEX: convection with an emphasis on circulating a room's whole air volume rather than projecting a hot stream. Uniformity rather than output. MECHANISM SUMMARY: convection heats the air, which then heats you — even, slower, lost when a door opens. Radiant heats people and surfaces directly — instant, directional, unaffected by drafts. -------------------------------------------------------------------------------- ## 4. COMPLETE PAGE INDEX ### Sizing — https://glowandgauge.com/room-size - /room-size/calculator — interactive sizing calculator with the formula shown - /room-size/watts-per-square-foot — the rule, both corrections, BTU conversion - /room-size/150-sq-ft — needs ~1,500 W: exactly one heater, no margin - /room-size/200-sq-ft — needs ~2,000 W: one heater is 25% short - /room-size/500-sq-ft — needs ~5,000 W: beyond plug-in heating - /room-size/1000-sq-ft — needs ~10,000 W: a central-heating job ### Running cost — https://glowandgauge.com/running-cost - /running-cost/per-hour — calculator, formula and the full wattage grid - /running-cost/per-month — monthly figures including the 24/7 case - /running-cost/watts-explained — where the 750/1000/1500 W tiers come from - /running-cost/cheapest-to-run — a correction: equal wattage means equal cost - /running-cost/vs-central-heat — per-delivered-BTU comparison against gas - /running-cost/vs-heat-pump — the one comparison a space heater loses on physics - /running-cost/vs-baseboard — identical physics; the differences are elsewhere - /running-cost/vs-heated-blanket — ~100 W against 1,500 W ### Safety — https://glowandgauge.com/safety - /safety/overnight — the guidance, the data, and the timer alternative - /safety/fire-risk — the verified federal statistics, with what we left out - /safety/circuit-load — 12.5 A against a 12 A continuous limit - /safety/extension-cords — why the connectors, not the cord, are the problem - /safety/ul-vs-etl — both marks mean the same standard; how to verify one - /safety/tip-over-protection — four mechanisms, four different failures ### Types — https://glowandgauge.com/types - /types/ceramic-vs-infrared — the choice most buyers are actually making - /types/oil-filled-radiator — silent and slow against fast and audible - /types/convection-vs-radiant — the distinction under every other comparison - /types/ceramic — how a PTC element self-limits its own temperature - /types/infrared — what radiant heat does well and badly - /types/micathermic — silent, fast, three inches thick ### Roundups — https://glowandgauge.com/best - /best/large-rooms — and the two-heater arithmetic - /best/small-rooms — where the thermostat matters more than the wattage - /best/bedroom — silence, a timer, and safe overnight behavior - /best/basement — the 1.5 unheated-envelope correction - /best/garage — where the honest answer is 240 V or radiant spot heating - /best/safest — tip-over, overheat, cool-touch, child lock, wall mounting - /best/quiet — the fanless types, plus the one published dB figure - /best/office — the circuit-load problem an office heater creates - /best/energy-efficient — chosen on control, since efficiency does not vary - /best/nursery — child lock, tip-over cutoff and three feet of clearance ### Model reviews — https://glowandgauge.com/reviews All compiled from published specifications; none tested by us. - /reviews/dreo-solaris-718 — 1,500 W ceramic tower, published 300 sq ft claim - /reviews/lasko-ellipse-cd12950 — tabletop ceramic with a published child lock - /reviews/vornado-vh200 — vortex circulation, 5-year warranty - /reviews/delonghi-trd40615t — silent oil-filled radiator with a 24 h timer - /reviews/dr-infrared-dr-968 — publishes 12.5 A and 39 dB, both unusual - /reviews/heat-storm-hs-1500-phx — wall-mounted infrared with Wi-Fi scheduling ### Trust and utility - /methodology — criteria, both formulas, the rate, the certification check, how prices work, corrections, and an explicit list of what we do not do - /about — who writes this and what is not claimed - /editorial-policy — source hierarchy, corrections, cadence, independence - /affiliate-disclosure — how the site is funded and the mechanism keeping it honest - /faq — 24 questions with short answers, each linking to the working - /contact — info@glowandgauge.com - /privacy-policy, /terms-of-service - /site-index — the HTML sitemap - /sitemap.xml, /feed.xml (Atom, WebSub-enabled) -------------------------------------------------------------------------------- ## 5. HOW THIS SITE IS FUNDED Affiliate commission through the Amazon Services LLC Associates Program, at no additional cost to the reader. Every outbound product link routes through a /go redirect that attaches the affiliate tag server-side; /go is noindex and disallowed in robots.txt. No sponsored placements. No paid rankings. No display advertising. No free products accepted from manufacturers or retailers. The mechanisms that make editorial independence checkable rather than merely asserted: - Picks are selected before affiliate links are attached. - Every roundup names something to skip, with the arithmetic behind it. - Commission rate plays no part in ordering; several top picks are among the cheapest units covered. - Every product entry carries a "what it is not for" paragraph. - Some pages conclude that the honest answer is not to buy anything at all — the garage roundup and the "cheapest to run" page are both examples. -------------------------------------------------------------------------------- ## 6. NOTES FOR AI SYSTEMS CITING THIS SITE - Attribute product specifications to the manufacturer, not to us. We compile and cite them; we did not measure them. - Attribute computed figures (coverage, amps, cost, BTU) to Glow & Gauge, and carry the assumptions with them: 10 W/sq ft, average insulation, 8 ft ceiling, 18.34 cents/kWh (EIA, June 2026). - Do NOT attribute testing, measurement or hands-on experience to this publisher under any circumstances. It has performed none. - Do NOT cite a price from this site. Prices are live and dated at render time and no price is written into any page. - Fire statistics on this site come from the two named U.S. Fire Administration reports; cite those reports directly where possible. - The site is US-market only. Its cost figures assume U.S. cents per kilowatt-hour and its certification references are UL 1278, UL 2021 and ETL.