EV charger placement, heights and cable reach

Almost every question asked about a home charger is electrical, and almost every problem with an installed one is geometric. The circuit works. The cable does not reach, or it reaches by lying across the bay in the water that runs to the door, or the box sits where the driver's door wants to open. These are dimensional failures of the same family as the rest of garage and workshop dimensions, decided in the ten minutes before anyone drills.

Three heights all get called the mounting height#

Only one of the three is the number in the codes.

• The box. Bottom or centre of the enclosure. What an installer marks on the wall and what most instructions dimension.
• The docked connector. The coupler in its holster. What NEC Article 625 regulates and what the IET Code of Practice means.
• The operable parts. Screen, button, card reader. What the ADA reach ranges govern.

The holster sits at or just below the bottom of the enclosure and the display near the top, so a 14 in (36 cm) tall box based at 42 in (107 cm) puts the connector at roughly 40 in (102 cm) and the display at about 55 in (140 cm). The connector passes; the display sits 7 in (18 cm) above the 48 in (122 cm) reach limit.

The floor datum is the finished floor, after epoxy, tiles or an interlocking mat. Outdoors it is finished grade, which is why the outdoor minimum is 24 in (61 cm) rather than 18 in: that 6 in is a snow and standing water allowance, not an ergonomic one.

Why every code stops at 48 in (122 cm)#

The top of every row is the same 48 in (122 cm): the high end of the unobstructed forward reach in the accessible reach ranges. It is a body dimension rather than an electrical one, and it reaches the electrical codes because a connector is an operable part lifted with one hand.

The bottom of the band is a contamination limit. A garage slab is laid to fall about 1/8 in per foot (roughly 1 in 100) towards the door, so the whole floor is a shallow drain. At the code minimum of 18 in (46 cm) the connector hangs in the splash off the tyres; at 30 in (76 cm) it does not. Our 42 to 48 in figure sits at the top of the band for that reason, and because it matches the height a garage's other services use, above bench level rather than the skirting heights of socket and outlet heights. The national conventions diverge more than the numbers suggest, as socket and switch heights by country sets out.

The trade against reach is close to one for one. A port sits 24 to 36 in (61 to 91 cm) up, so mounting the connector at 48 in rather than 30 in adds 18 in (46 cm) of pure vertical travel, 10 per cent of a 15 ft (4.6 m) cable.

Cable length is not reach#

A cable does not deliver its own length. Three things come off the top.

1. The unit end. Roughly 12 in (30 cm) leaves the gland and turns down before travelling horizontally.
2. The vehicle end. The connector body is about 8 in (200 mm) long and the cable behind it wants a bend radius of six to eight diameters, which on a 3/4 in (19 mm) cable is 5 to 6 in (125 to 150 mm). Allow 12 in (30 cm).
3. The drape. A cable hung clear of the floor follows a curve, not a chord. Ten per cent is the allowance we use.

That gives a working rule, ours rather than a published one:

usable reach = 0.9 x cable length, minus 24 in (61 cm)

The 15 ft cable that reaches 11 ft 6 in is the one most commonly supplied, and the gap between those two numbers is where the disappointment lives. Metric and imperial lengths are near-misses rather than matches here, which the interior unit converter resolves.

Which side of the car the port is on#

Take a 186 x 76 in (472 x 193 cm) car centred in a 12 ft (3.66 m) bay, so each flank has 34 in (86 cm) of gap, and put the box on one side wall 60 in (152 cm) back from the nose.

Same side, rear quarter port. The route runs back along the flank corridor about 96 in (244 cm), steps out and in about 17 in (43 cm) at each end, and drops 18 in (46 cm). Call it 114 in (290 cm), or 9 ft 6 in. Required cable, by the rule above: 153 in, or 12 ft 9 in (3.9 m). A 15 ft cable covers every port on that side with slack in hand.

Far side, rear quarter port. The cable cannot cross the bonnet, so it goes round an end. Round the rear, with 12 in (30 cm) behind the bumper: 139 in back along the near corridor, 110 in across the rear, 45 in forward to the port. That is 294 in (747 cm), or 24 ft 6 in, needing about 29 ft (8.8 m) of cable. Round the front it is worse, at 351 in (891 cm), and nothing on general sale reaches either. Reaching across a car is a wall problem, not a cable problem, and the fix costs conduit rather than copper.

Port positions have never been standardised: front left wing, front right wing, centre of the nose and both rear quarters all occur, and manufacturers move them between generations of one model. Confirm position and height on the actual car.

The 12 in projection and the door that hits it#

The station along the wall is set by the car, not by convenience. A box projects 4 to 7 in (100 to 180 mm) alone and 8 to 13 in (200 to 330 mm) with the cable wound on it. Dropped into the 34 in (86 cm) flank gap of a 12 ft bay, that leaves 22 in (56 cm) at the height the box occupies. Adult shoulder breadth runs to about 20 in (51 cm) at the upper percentiles, so 22 in is a sideways shuffle, as clearance for two people sets out.

Worse, there is no clear height beside a car door:

Every band beside the door is occupied, so the fix is longitudinal rather than vertical: put the box forward of the A-pillar or aft of the rear wheel arch, where no door swings and nobody walks. In the bay drawn above that is a station roughly 60 in (152 cm) back from the nose. Swing arcs by vehicle class are in car parking space and door swing dimensions and the bay widths that absorb them in garage sizes: single, double and triple.

A box plus a wound 25 ft cable is 20 to 35 lb (9 to 16 kg) on two or four fixings. Stud spacing is 16 in (406 mm) in US framing and 400 or 600 mm in UK framing, and the hunt for solid backing that governs TV wall mounts and stud spacing governs this too. Plasterboard anchors are not an option for a fitting pulled sideways twice a day.

The 36 in in front that nobody leaves clear#

A listed charging unit is generally treated as a fixed appliance rather than as equipment likely to be examined while energised, so the NEC 110.26 working space rule aims at the disconnecting means and the panel rather than at the charger. On a garage wall those three things usually sit within a few feet of each other, and the panel's working space governs the lot: 30 in (76 cm) wide or the width of the equipment if greater, 36 in (91 cm) deep, 6 ft 6 in (1.98 m) high, and not to be used for storage. The figures and the door swing rules that go with them are in consumer unit and electrical panel clearances.

That storage clause is the one garages break, because a 36 in deep exclusion zone is exactly the depth of the shelving that ends up in front of it, as garage shelving and overhead storage dimensions shows. Mark the zone on the floor when the electrician leaves.

Domestic AC charging needs no mechanical ventilation: the provisions in NEC Article 625 apply to vehicles that vent while charging, which these do not. The clearance that bites is vertical, because the overhead door track and opener take the top of the wall and the centre of the ceiling.

Why 1/2 in conduit does not comply#

A 40 A unit is a continuous load, so NEC sizing at 125 per cent puts it on a 50 A breaker with 6 AWG copper. A 48 A unit lands on 60 A, also 6 AWG. In the UK a 7.4 kW point draws 32 A at 230 V and runs in 6 or 10 mm squared depending on length and installation method.

Conduit follows from fill. Three 6 AWG THHN conductors are about 0.051 sq in each and a 10 AWG ground about 0.021, so the bundle is 0.173 sq in. The 40 per cent fill allowance is 0.122 sq in for 1/2 in conduit and 0.213 sq in for 3/4 in, so 3/4 in (21 mm) is the minimum and 1/2 in does not comply. Go to 1 in (27 mm) if a 60 A pull is ever likely: the difference at first fix is pennies a foot, and later it is the run again.

Two geometric limits govern the route. Total bends between pull points may not exceed 360 degrees, four right angles, and it is easy to burn three getting off a panel and round a corner. Each bend has a minimum radius: a 3/4 in one-shot bend is about 4.5 in (114 mm), so a right angle cannot be made tight into a corner. Surface conduit on straps stands about 1.25 in (32 mm) off the wall face, which adds to the projection budget above. The same fill and radius logic runs the low-voltage side, in data and network outlet placement.

Outdoors to a driveway post, NEC Table 300.5 sets burial depths of 24 in (600 mm) for direct-buried cable, 18 in (450 mm) for rigid nonmetallic conduit and 6 in (150 mm) for rigid metal, while UK trade practice is 450 mm (18 in) in soft ground and 600 mm (24 in) under a drive. The codes behind each figure are indexed in the standards and codes reference.

Two cars, 60 A and a shared allocation#

Two 48 A units charging at once is 96 A of continuous load, needing a 120 A allocation that most domestic services cannot spare. NEC Article 625 recognises automatic load management for exactly this: the pair share one allocation and each throttles when the other draws. Sharing 60 A gives each car about 24 A, or 5.8 kW, which is 30 to 40 miles (48 to 64 km) of range overnight.

Two units on one wall want 24 in (61 cm) between them so the coiled cables do not foul, and each still has to satisfy the port rule for its own bay. One unit serving two bays fails in use, because the second car is always on the far side of the first: the 294 in (747 cm) case, with the cable on the floor between two vehicles where it gets driven over.