12V vs 24V Security Systems: Which Voltage Should Installers Use?

Choose 12V or 24V security power by checking the equipment first, then the cable run and backup requirements. For compatible equipment delivering similar power, 24V can reduce current and cable losses. However, a 12V-only alarm panel, reader or intercom must remain within its specified input range. The most suitable commercial installation may use 24V for locks and a separately regulated 12V supply for control electronics.

This guide helps New Zealand security installers choose a power architecture before ordering equipment. It covers DC systems; 24VAC and 24VDC are different supplies and must never be treated as interchangeable unless the exact equipment documentation permits both.

12V vs 24V security systems: the practical choice

Voltage alone does not determine reliability, holding force, standby duration or compliance. These depend on the selected products and complete installation. Start with the security power supply range, then narrow the selection using a load schedule rather than choosing the largest current rating.

Start with each device's allowed input range

Record the exact model, hardware variant, AC or DC input, polarity, allowable voltage range, normal current and maximum operating current. Include readers, controllers, door stations, locks, request-to-exit devices and auxiliary interfaces. The voltage printed on the enclosure is a starting point, not a substitute for the installation manual.

A nominal 12V battery-backed rail may operate above 12V while charging and below it during discharge. Check that every connected device accepts the entire intended range. Repeat the exercise for a nominal 24V rail. Do not assume all 12V devices accept 13.8V or that all 24V devices accept a particular charging voltage.

The ITPSA12-5AMP regulated supply is listed for 12V DC applications. Selecting a regulated supply does not, by itself, establish battery charging or standby capability. Confirm those functions separately before including any plug-in supply in an outage-resilience design.

Why 24V can help with longer cable runs

For DC power, current equals power divided by voltage: I = P / V. Cable voltage drop equals current multiplied by the complete circuit resistance: Vdrop = I × Rloop. Include the outgoing and return conductors. A 50m route normally means 100m of conductor in a simple two-wire circuit.

As a calculated illustration, suppose a compatible load takes 12W at either operating voltage and the complete cable loop has 2Ω resistance. This is an assumed design example, not a cable specification or a tested product result.

These are first-pass calculations using nominal current. A regulated constant-power load can draw more current as its input falls, while a coil may behave differently. Use manufacturer maximum current and cable resistance at the relevant temperature, then measure the finished circuit under load. Add connector, fuse, relay and distribution losses. The resulting terminal voltage must remain above the device's minimum during its worst operating condition and on battery power.

Use the voltage-drop calculator on our Online Tools page to explore a proposed cable run. Confirm its inputs against the actual cable and equipment data. Changing voltage is not a substitute for correcting undersized conductors, damaged joints or an overloaded supply.

Check lock current instead of assuming it halves

A dual-voltage lock is useful when the door design supports either supply, but the current relationship is model-specific. Securitron's M32, M62 and M82 installation instructions list the M32 at 300mA on 12V and 150mA on 24V. The same table lists the M62 at 250mA and 150mA respectively. The current does not halve for every model.

For an electric strike, motorised lock or bolt, distinguish starting, operating and holding current. A door that releases correctly on a short bench cable may fail after installation when several doors operate together. Check the manufacturer's duty cycle, voltage configuration and suppression instructions for the exact lock.

Keep relay contact ratings separate from the controller's own supply rating. A dry relay contact does not create lock power. Check its DC switching rating and suitability for the load, and follow the interface manufacturer's requirements. Our intercom door release wiring guide explains the distinction between the release command and the lock's power circuit.

Plan separate rails for mixed 12V and 24V equipment

A commercial door may need a 24V lock circuit alongside 12V control equipment. Use separate compatible supplies, a documented dual-output system or a suitably rated DC-to-DC converter. A selectable 12V-or-24V output is not necessarily a simultaneous dual-voltage output.

For example, Altronix describes its AL400XB2V as a single selectable output, with 4A available at 12V or 3A at 24V. This illustrates why both voltage mode and mode-specific capacity must be checked. It is a documentation example, not a claim that this model suits every NZ project or is stocked by Essential Security Supplies.

The FERN360 FPAC-BPO150 power supply board is another product to discuss when planning a modular power enclosure. Confirm the current installation documentation, output configuration, charger allocation and enclosure requirements with technical support before specifying it. Do not derive available load current solely from the product's headline wattage.

For a converter, check its input range throughout battery discharge, output capacity at enclosure temperature, conversion losses, protection and whether isolation is required. Do not feed a 12V circuit from the midpoint of a 24V series battery string. Use the intended regulated architecture, with returns and earthing arranged according to the equipment instructions.

Size battery backup in watt-hours as well as amp-hours

Two compatible 12V 7Ah batteries connected in series form a nominal 24V 7Ah string, not 24V 14Ah. Nominal energy is approximately 168Wh, compared with 84Wh for one 12V 7Ah battery. Those figures describe nominal stored energy, not guaranteed usable energy or standby time. Power-Sonic explains the voltage and capacity distinction in its series and parallel battery guidance.

The Century PS1270 12V 7Ah battery is a catalogue example for a compatible standby design. Confirm chemistry, terminal type, capacity, cabinet space and charger approval for the selected power supply. Use matched batteries as required by the manufacturer; do not mix an old battery with a new one in a series replacement.

A useful first estimate is standby energy = standby watts × hours, plus energy for additional operating events. Then allow for conversion losses, battery ageing, temperature, discharge rate and the equipment's low-voltage cutoff. Use battery discharge data to confirm capacity. Higher voltage does not automatically provide longer backup when total stored energy and load power are equal.

Also check recharge performance while normal loads remain connected. Use the separate access control power supply sizing guide for the load-budget process. This voltage guide owns the choice of supply architecture rather than replacing the detailed sizing exercise.

Commission the voltage choice at the actual door

Before handover, test the completed installation against the approved design and manufacturer instructions. A cabinet measurement alone cannot show what a remote lock receives.

1. Record each device's model, allowed input range, selected voltage and required polarity.
2. Measure the supply and the furthest device under normal load and the highest expected simultaneous operating load.
3. Repeat functional checks on battery operation using the manufacturer's approved test procedure. Do not deliberately deep-discharge batteries to prove runtime.
4. Confirm branch protection, conductor ratings, converter capacity and enclosure temperature limits.
5. Test fault reporting, loss of mains and the documented response to a disconnected or failed battery where supported.
6. Verify required door release and emergency interfaces against the approved site sequence, including behaviour during power failure.
7. Label voltage rails, protection devices and field cables, then leave measured readings and battery details in the handover record.

For NZ projects, allocate mains-side work to an appropriately licensed electrical worker and confirm the applicable certification requirements. See WorkSafe's guidance on getting electrical work done. A 12V or 24V label does not establish that the complete cabinet or installation is electrically safe, or that an access-controlled door meets its fire and egress requirements.

Frequently asked questions

Is 24V always better than 12V for access control?

No. It can reduce cable losses for compatible loads, but equipment input requirements come first. A mixed system may use 24V locks and separately regulated 12V electronics. Select the architecture from the device schedule and verify the complete operating range.

Can I connect a 12V security device to a 24V supply?

Only if the exact device documentation explicitly permits that input. Otherwise use a suitable regulated converter or separate supply. A matching connector or a relay rated to switch 24V does not make the device's power input compatible.

Does a 24V system double battery standby time?

Not simply because of its voltage. Runtime depends on usable battery energy, total load and losses. Two 12V batteries in series provide more nominal energy than one identical battery because there are two batteries; the string's amp-hour rating remains unchanged.

Can I change an existing 12V installation to 24V?

Only after checking every connected device, lock configuration, relay, converter, charger and battery arrangement. Isolate and reconfigure equipment using the manufacturer's procedure, update labels and drawings, and recommission the system. Never change a supply selector with unverified equipment connected.

Get the security power design checked before ordering

Send Essential Security Supplies your door schedule, exact equipment models, cable lengths and conductor sizes, simultaneous operating loads and required standby period. Include any fire-interface or release-sequence requirements. We can help identify suitable power supplies, batteries and distribution components for technical review and a project quotation.

Request 12V or 24V specification assistance from Essential Security Supplies, or call 09 415 1500.