LowVoltCalc
Tools

Sources and method

Every number these calculators use, where it comes from, and the few we could not source.

How we work

  • Every constant is cited in the code and on the page that uses it.
  • Where a standard is behind a paywall, we name the standard, edition and table, and the published source we checked the value against.
  • Where no source exists, the number is labelled as unsourced and is only allowed to make a plan larger, never smaller.
  • Every calculation is a plain function, tested against worked examples from its source before it ships.
  • Everything runs in your browser. Nothing you enter is sent anywhere; the link you share holds the inputs, after the # where servers never see it.

If you find a number that is wrong, tell us and include your source. Corrections are welcome.

Voltage drop

  1. NFPA 70, National Electrical Code, Chapter 9, Table 8, Conductor Properties. DC resistance at 75 °C of uncoated copper, solid and stranded, 18 to 2 AWG; Note 2: R₂ = R₁[1 + α(T₂ − 75)], α = 0.00323. Checked against the 2017 and 2011 editions, which agree.
  2. NBS Handbook 100, Copper Wire Tables (1966), nvlpubs.nist.gov. The basis Table 8 cites. Table 6: 22 AWG 19.7 Ω/kft and 24 AWG 31.2 Ω/kft at 75 °C; IACS resistivity 1.7241 µΩ·cm at 20 °C; α₂₀ = 0.00393; the AWG diameter series.
  3. IEC 60228, Conductors of insulated cables (Table 2 in the 2004 edition, Table 4 in 2023). Class 2 plain copper, maximum resistance at 20 °C, 0.5 to 16 mm². Checked against Nexans' reproduction and Lapp's catalogue.

Camera storage and bandwidth

  1. Hikvision, H.264(5) & H.264(5)+ Recommended Bit Rate at General Resolutions, hikvision.com. The base bit rate per resolution and codec, and Note 1: complex scenes +20–30%.
  2. Hikvision, H.265+ Encoding Technology: Halve Your Bandwidth and Storage, hikvision.com. Measured 1080p/25 fps scenes (the low- and high-motion ranges) and H.265+ savings.
  3. Bosch, DINION IP starlight 8000 MP datasheet (2016). Typical bit rates by frame rate (the moderate-motion lower bound and the frame-rate curve).
  4. IPVM, Frame Rate Guide for Video Surveillance, ipvm.com. Measured bit rate at 1, 10 and 30 fps.
  5. IPVM, Axis Zipstream report and Bandwidth Guide for Video Networks (2020). Independent smart-codec results, including the 12% lower bound. IPVM on calculator accuracy: ipvm.com.
  6. Ohm, Sullivan, Schwarz, Tan and Wiegand, Comparison of the Coding Efficiency of Video Coding Standards—Including HEVC, IEEE TCSVT 22(12), 2012, ieeexplore.ieee.org.
  7. Axis, H.264 video compression standard (2008): MJPEG and MPEG-4 ratios. Axis Zipstream technology, whitepapers.axis.com.
  8. Smart-codec claims: Dahua, Hanwha WiseStream II, Uniview, Bosch iDNR white paper (2013), Avigilon, i-PRO.
  9. Seagate, drive capacity, seagate.com: 1 TB = 10¹² bytes. Synology, Choose a RAID Type, kb.synology.com, and the RAID calculator notes (ext4 2%, Btrfs 4%).

PoE power budget

  1. IEEE Std 802.3, Clause 33 and Clause 145, as tabulated in Sifos Technologies' PoE overview and IEEE's 2017 PoE tutorial. Class power at switch and device; minimum PSE voltage per Type.
  2. Ethernet Alliance, PoE – Cable Losses (2017), ethernetalliance.org. Channel resistance (20 Ω, 12.5 Ω, 6.25 Ω) and worst-case losses, which the calculator's model reproduces.

Battery standby

  1. NFPA 72 (2022), 10.6.7.2.1 (24 h standby, 5 or 15 min alarm), 10.6.7.2.14 (factor 1.25), 24.10.2.1 (two-way emergency communications). Checked against the Talk-A-Phone 2022 worksheet, ESA and National Training Center summaries.
  2. UL 294, 7th edition, 41.3–41.6: standby power levels I to IV, from UL's published preview.
  3. NFPA 101, 7.2.1.6.2, and IBC sensor-release provisions, for locks on loss of power.

Off-grid solar

  1. Sandia National Laboratories, Stand-Alone Photovoltaic Systems: A Handbook of Recommended Design Practices, SAND87-7023 (updated March 1995), from Sandia's photovoltaics site via the Internet Archive. The method; Appendix B worksheet defaults (wire efficiency 0.98, 1.20 × battery voltage to charge, round-up rules); the storage-days chart (block 30), read at each whole peak sun hour; tilt latitude + 15° for winter loads; modules rated at 45 °C. Point Design No. 5, a VHF radio repeater, is reproduced number for number by the tests.
  2. NREL PVWatts version 8 API, developer.nlr.gov (NREL is now the National Laboratory of the Rockies). The worst-month sun for the 48 listed cities: NSRDB typical-year data (PSM v3, TMY 2020; PSM v4 polar, TMY 2023, for Anchorage and Fairbanks), fixed open-rack array facing south at latitude + 15°, monthly plane-of-array irradiance (kWh/m²/day = peak sun hours). Fetched once in November 2026 and stored with the calculator; nothing is fetched when you use it.
  3. A. P. Dobos, PVWatts Version 5 Manual, NREL/TP-6A20-62641 (2014), nlr.gov. Table 6 system losses (14% default), Table 3 temperature coefficient for a standard module (−0.47 %/°C), 45 °C operating temperature for an open rack, Eqn. 8.
  4. Victron Energy, 12,8 Volt lithium iron phosphate batteries Smart, victronenergy.de. Round-trip efficiency (LFP 92%, average lead-acid 80%), capacity at 0 °C and −20 °C, charge +5 to +50 °C, discharge from −20 °C, cycle life at 80% DoD.
  5. Trojan Battery, User's Guide (flooded, AGM, gel). Figure 9 capacity vs temperature (read at each 20 °F gridline), 80% depth-of-discharge limit, −20 °C operating limit, Table 7 state of charge vs specific gravity, freezing point of electrolyte (BCI, 1995). Trojan GC2 Series Lithium-Ion Batteries User's Guide (2023): charging below 32 °F prohibited.
  6. Battle Born Batteries, BB10012 data sheet: charge temperature 25 °F to 135 °F, discharge from −4 °F, heated model 28 W.
  7. Victron Energy, SmartSolar MPPT 75/10 to 100/20 datasheet: 98% peak efficiency, 100 V maximum PV voltage, PV voltage above Vbat + 5 V to start and Vbat + 1 V to run, 25 mA own draw at 12 V. Morningstar, Traditional PWM vs. TrakStar MPPT Technology (2015): a PWM controller pulls the array down to battery voltage.
  8. NFPA 70 (2023), 690.8(A)(1) (Isc × 125%) and 690.8(B)(1) (a further 125% for conductors and overcurrent devices), as summarised by Mike Holt, EC&M, 2024; 690.7 cold open-circuit voltage from the module's coefficient, with J. Wiles' worked example, IAEI Magazine, 2019.
  9. Device and panel datasheets: IEEE 802.3 PoE class maximums (as on the PoE page); Ubiquiti NanoStation 5AC Loco 7 W; Teltonika RUT241 user manual, under 6.5 W (and Teltonika's measured 1.5 to 3.3 W); Hikvision DS-7600NI-K1/A (B) series, 10 W without a drive; WD Purple product brief, 4 TB 4.7 W; Tycon TP-DCDC Gigabit, 75% minimum efficiency and 1 W own draw; Renogy RNG-100D-SS (V2.1) and RSP200D (G3); Canadian Solar HiKu6 CS6R-MS.

Conduit fill

  1. NFPA 70, Chapter 9, Table 1 and its Notes, and Table 4. Checked against the 2017 edition's text. 800.110(B) (2017): communications cables and raceway fill.
  2. Cable diameters from Belden datasheets (1583A, 2412, 3612, 3613, 10GX13, 6320UL, 5502UE, 5300FE, 1694A, 1505A) and West Penn AC251822B.

Cable run lengths

  1. ANSI/TIA-568.0-E (2020), 5.10.2.2, formula (3).
  2. IEEE 802.3bz via Fluke Networks; Ethernet Alliance 10GBASE-T white paper, Table 3; TIA TSB-155.
  3. HDBaseT Alliance; ATEN VE901 datasheet for Class B.
  4. Texas Instruments SLLA070D for RS-485; OSSI and DSX for Wiegand.

Camera network IP planner

  1. RFC 950, Internet Standard Subnetting Procedure, rfc-editor.org. Subnet masks; the all-zeros and all-ones host addresses are not assigned.
  2. RFC 4632, Classless Inter-domain Routing (CIDR), rfc-editor.org. Prefix notation; a /n holds 2^(32 − n) addresses.
  3. RFC 3021, Using 31-Bit Prefixes on IPv4 Point-to-Point Links, rfc-editor.org.
  4. RFC 1918, Address Allocation for Private Internets, rfc-editor.org.
  5. RFC 1878, Variable Length Subnet Table for IPv4, rfc-editor.org. The table the tests check every prefix against.
  6. Factory default addresses, each from the maker's own documentation: Hikvision camera user manual V5.5.90; Dahua camera Web 5.0 operation manual and NVR quick start guide; Honeywell Performance Series quick guide; Axis, "How to assign an IP address"; Hanwha Vision support; Bosch AUTODOME IP starlight 5000i manual; Uniview camera user manual V3.00 and 3-Series NVR quick guide; i-PRO WV-X25700 web guide; Lorex X Series FAQs; Pelco Sarix Professional manual. Each is linked from the planner's table.

What we could not source, and what we did instead

  • The 2023 NEC text itself. NEC tables are checked against the 2017 edition (Tables 1, 4, 8) and 2011 (Table 8). Secondary sources that follow the 2023 edition show the same Table 8 values.
  • Camera encoder "quality" settings. No published figure. Lower quality may save up to 30%, higher may cost up to 50%; the plan's upper end is never lowered for it.
  • Simple scenes. No published reduction, so none is applied.
  • Frame rates above 30 fps. Scaled in proportion, which overstates.
  • Resolutions outside 352×288 to 12MP. Extrapolated from the published table and flagged.
  • Smart codecs with only an "up to" claim (Dahua, Hanwha, Uniview, Avigilon, i-PRO): the least saving is set to 12%, the lowest published measurement for any smart codec.
  • H.265 versus H.264 per scene. The model uses Hikvision's table, about half; vendor tests measured 33% to 73%.
  • An access-control battery factor. UL 294 sets none; 1.25 is offered as a labelled default.
  • Factory default addresses for Amcrest, Reolink and Hikvision NVRs: their own documents give none, so the planner does not warn about them. UniFi's only statement is in a legacy guide, so it is left out too.
  • AGM in the cold. Trojan publishes its capacity curve for flooded batteries; the solar calculator uses it for AGM too, which can only overstate the battery.
  • A panel's Voc and Isc temperature coefficients when you enter your own panel: the power coefficient is used for Voc, and 0.05 %/°C (the largest of the three preset datasheets) for Isc. Both can only add panels in series.
  • Charts read by eye. Sandia's storage-days chart and Trojan's temperature curve are published as graphs; the values are read at their gridlines and interpolated in straight lines. Storage days are rounded up.
  • Camera power by the hour. No figure splits a camera's IR-on night draw from its day draw in a way we can apply generally; the solar calculator uses the maximum for all 24 hours.
  • A "large system" line. The solar calculator warns above 1,000 W of panels or 10 kWh of battery. That is our line for when a pole-top kit stops being one, not a code limit; it changes no size.
  • Headroom for recorders. No standard sets it; it is yours to choose, and defaults to 0.