I have watched more bathroom renovations go sideways over wiring than over tile or plumbing. Water gets the spotlight, yet electricity does the quiet heavy lifting that makes a bathroom feel modern and safe. You notice it when it fails: the mirror that fogs because the fan never lived up to its rating, the outlet that trips when you plug in a hair dryer, the light that casts a mortuary pallor at 6 a.m. Get the electrical planning right, and the rest of the room behaves.
This is the stuff I wish someone had told me before I learned it on ladders with a headlamp clenched in my teeth.
Start with the loads, not the fixtures
A good bathroom electrical plan starts on paper with real-world loads. Appliances today dwarf the dainty demands we used to see. Hair dryers and curling irons draw 12 to 15 amps each. Steam showers, heated floors, bidet seats, and towel warmers all add up. Pretend your bathroom is a tiny kitchen for a minute, then size the circuits accordingly.
For a typical primary bath in a North American home, I plan at least two 20-amp circuits for receptacles alone. That sounds generous until you think about a pair of GFCI-protected outlets at the vanity feeding two adults rushing out the door with dueling hair tools. Sharing that with the fan, lights, and radiant heat is a recipe for nuisance trips. When the drywall closes, your options narrow, so buy future peace with dedicated capacity.
I have also installed dedicated 15- or 20-amp circuits for a bidet seat and for a towel warmer more times than I can count. Both feel optional at the design stage and end up as must-haves later. Give them their own home on the panel and you never think about them again.
Code is the floor, not the ceiling
Most places require GFCI protection for all bathroom outlets and any receptacle within a certain distance of a sink. If a whirlpool tub or spa-like shower appears on your plan, bonding and GFCI rules tighten. Exhaust fan timers, damp-location rated fixtures, and correct box fill all follow. The code, though, sets a minimum standard. It does not care if your partner trips the breaker every third morning or if your mirror light turns your skin green.
I design with headroom and usability. If a 12-amp hair dryer plus a 4-amp curling iron is a likely scenario, I give the vanity its own 20-amp circuit. If the bathroom has no window, I choose an exhaust fan that can actually clear the space and then give it a smart control so users cannot forget to run it. If a walk-in shower has a dark corner, I plan a low-voltage LED downlight rated for wet locations, with the transformer accessible, not entombed.
The two principles I use are redundancy and isolation. Redundancy makes sure you can lose one thing without losing the room, like keeping the vanity lights on a different circuit from the exhaust fan. Isolation keeps noisy or high-draw items separate: heated floors, towel warmers, bidets, steam generators.
GFCI and AFCI without the alphabet soup headache
The ground-fault circuit interrupter is non-negotiable in wet spaces. It compares current on the hot and neutral and trips quickly when even a small imbalance suggests electricity is taking a bad path, possibly through you. Whether you provide GFCI at the breaker in the panel or in a receptacle in the bathroom depends on panel accessibility, downstream load coverage, and how many bathrooms tie to the same circuit. I prefer GFCI breakers for fresh renovations when the existing panel supports them, because it simplifies the number of reset points and keeps the devices in the bathroom slimmer. If I have a single vanity receptacle I want to protect and I do not plan to string others downstream, a GFCI receptacle is just fine.
Arc-fault protection shows up in newer codes even for bathroom lighting circuits. It helps catch series and parallel arcs from damaged conductors or loose connections, which can start fires inside walls. Combination AFCI/GFCI breakers save panel space and reduce finger-pointing when something trips. If you have never lived with an AFCI breaker, be ready for it to tattle on lazy wire-nut twists. That is a good thing, even if it means redoing a few splices you thought were fine.
The vanity: where lighting design meets morning reality
You can spot the bathrooms where nobody thought about human faces. A single ceiling can creates deep eye sockets and a strip light high above the mirror throws shadows that belong in a film noir. Vanity lighting should wash the face evenly from the sides, not the top. That means sconces flanking the mirror or a vertically oriented fixture at the edges of a wide mirror. Mounting height usually lands with the center of the sconce 60 to 66 inches off the finished floor, but the real measure is the face in the mirror. Mock it up with painter’s tape and a flashlight before you commit.
Color matters. A color rendering index (CRI) above 90 exposes skin tones without turning anyone vampiric. Aim for 2700 to 3000 Kelvin if you want a warm tone that flatters at dawn and dusk, or 3000 to 3500 K if you like a bit more pop. Avoid the 4000 K plus territory unless you are running a clinic. I have replaced more cool-blue vanity fixtures than I have installed. They looked crisp on the box and harsh on real faces.
Dimmers pay off here. I use ELV or 0 to 10 volt compatibility for LED fixtures rather than cheap phase-cut dimmers that flicker or step. If you cannot justify an integrated dimmer at the wall, at least use dimmable LED lamps and a reputable, LED-rated dimmer. The first time you sneak into a bathroom at 3 a.m. and the light stays at 10 percent, you will thank Past You for thinking ahead.
Mirrors that do more than reflect
Backlit mirrors and defogging mirrors have matured. The cheap ones hum and take a lifetime to clear condensation. The good ones warm the glass evenly and sip power. A typical anti-fog pad draws 20 to 60 watts. I have seen units with their own touch switch hidden behind the glass, and others that need a hardwired wall switch. Both work, but think through user behavior. If the switch is on the other side of the room, nobody will use it. My default is to pair the mirror heater with the exhaust fan on a timer, or give it a discreet local switch. Keep access to any driver or transformer, because mirrors die faster than walls do, and you do not want to demo tile to replace what amounts to a big, fancy light.
If you like lit mirrors but also want task flexibility, plan for an outlet inside the vanity or medicine cabinet. The clean-counterlook sells, but it only holds up if people can actually stash their toothbrush chargers and shavers somewhere that has power.
Exhaust: cfm numbers lie if the ductwork does
Homeowners love the advertised cfm on a bathroom fan. I love the actual cfm at the grille, which depends as much on the duct as the motor. A fan rated 110 cfm with a long flex run and three elbows can act like a 50 cfm toy. Whenever I can, I run rigid duct with smooth interior walls, keep the run short, and use long sweep elbows. A 6-inch duct helps more than a beefier fan.
Sizing is about more than air changes per hour. For a standard bath with a shower, 80 to 110 cfm keeps up. For a big primary bath with a separate water closet and a soaking tub, I often install two fans: one in the main area, one over or near the shower, each on their own switch. Smart humidity-sensing fans are better than they used to be, but they still guess. A wall timer that runs 20 to 40 minutes after you leave beats the “set and forget” hope of sensors when multiple showers fog the place.
Noise ratings matter because people will not run a noisy fan. Target less than 1.5 sones, and you can go quieter. A truly whisper fan encourages use, which protects paint, trim, and grout from steam more than any sealer.
Heated floors, towel warmers, and the honesty of watts
Electric radiant floors feel luxurious and keep tile bone-dry. They also demand planning. The mat goes under tile or stone, on top of a decoupling membrane or thinset, and the thermostat needs a floor sensor lead routed back to the control box. The mat watt density commonly sits around 12 to 15 watts per square foot. A modest 50 square foot heated area can pull 600 to 750 watts. That is a dedicated 15-amp circuit in some cases, or it can share a 20-amp if the total load allows. What you cannot do is wedge the thermostat in a 14-cubic-inch box with three cables and wish for the best. Give it a deep box and space for low-voltage sensor wires and line voltage supply in a clean separation.
Towel warmers vary wildly. Wall-mounted hydronic models tie to hot-water heating loops, but most retrofits use electric units between 50 and 200 watts. A plug-in unit looks easy, then the cord mars your clean line. Hardwired is tidy and safer in a wet space, but you need a junction box at a specific height and location. The thermostat or on-board timer matters too, because nobody wants to run a warmer all day. My favorite layout puts the towel warmer near, not inside, the splash zone, with a nearby wall control that your hand finds instinctively as you step into the shower.
Safe zones and the splash map
Every bathroom has zones in my head: the soak zone around the tub, the spray zone around the shower, and the splash zone near the sink. Light fixtures and receptacles need to respect those invisible boundaries. Inside the shower, pick only wet-location rated lights. Over a tub, damp-location can pass if it is far enough away from spray and condensation, but I still vet the exact placement against the fixture’s spec sheet. Sconces near a vanity can be damp-location rated and still look like jewelry.
The receptacle near a sink should be no more than a foot or so from the outside edge of the basin if you expect hair tools to reach the mirror. What you do not want is an outlet tucked behind a sink pedestal where cords dangle in water or a bulky GFCI device that crowds the backsplash. I keep outlets 12 to 20 inches above the counter, centered between sinks when I can, and I break from that rule when a medicine cabinet with an interior outlet turns out to be the smarter bet for a particular family. A single teenager with a curling iron creates different needs than a couple with electric toothbrushes and a rechargeable trimmer.
The case for more boxes than you think you need
You can overdo technology in a bathroom, but you cannot magically add a box behind tile without swearing and dust. I rough in for more and then cap what I do not need. A blank plate hidden inside a vanity is not a failure, it is a hedge against later regret. The same goes for low-voltage provisions. A Cat6 or two to the medicine cabinet or vanity gives you options for a smart mirror, a control panel for a steam shower, or a future speaker. If you never use it, the cable sleeps in the wall. If you do, you are a genius to your future self.
If I am adding a steam generator, I run a dedicated circuit sized to the unit’s nameplate and I still leave a chase or conduit for a future upgrade. Steam owners tend to upgrade. The person who invests in that system today rarely rips it out later.
Lighting layers for a small room that pulls big duty
A layered lighting plan in a bathroom sounds like a showroom phrase until you live with it. The ambient layer fills the room without glare. The task layer lights the face and the work zones. The accent layer adds a bit of delight, like a toe-kick LED strip that turns on for night navigation, or a backlit niche in a shower.
Toe-kick lighting works best low voltage, 24-volt LED tape with a driver tucked in an accessible place like the vanity or a nearby closet. Tie it to a motion sensor set to a low level at night, and you get a soft runway that does not jar you awake. Use aluminum channels with diffusers so the light feels continuous, not like a dotted line.
For ambient light, I often prefer a linear ceiling fixture over cans in small baths. A flush or semi-flush with good diffusion and a high CRI fills the space more evenly with less Swiss cheese in the ceiling. In larger baths, a grid of two or three recessed fixtures sized to avoid hitting joists keeps the room bright without drama. Recessed lights in showers need wet-location ratings and clearances from insulation and vapor barriers. Airtight housings help keep warm, moist air from sneaking into the attic through the can’s gaps.
Switch logic that survives groggy mornings
Put controls where your hand goes naturally. That sounds like advice for toddlers, but it is surprisingly easy to ignore on paper. The first switch by the door should control something you want immediately, usually a gentle ambient light. The second switch can be the vanity task lights. The exhaust fan belongs on a timer or a humidistat that you can override, not on the same switch as the lights unless you want to hear it every time someone washes their hands.
Three-way switching near the entry and at the far end of a long bath or water closet pays off. Motion sensors sound great until you sit still long enough for the lights to go out. Use vacancy sensors, not occupancy sensors, in bathrooms when you can, so you turn the lights on deliberately and they turn off after a set period.
Smart switches can help, but only if the household will use them. An app slider for a shower niche light nobody cares about is dead weight. A simple scene that keeps night lighting dim and skips the fan after a quick midnight visit, though, earns its keep.
Working in old walls, and the compromises that keep you sane
Older homes hide surprises. Plaster walls, shallow boxes, knob-and-tube out of sight, joists you would not dare drill. In those spaces, I try to preserve plaster where possible and use surface raceways neatly, or take advantage of tall baseboards to run new lines. Shallow pancake boxes for sconces on old masonry work, but be mindful of fixture backplates that need more depth. If a run across the ceiling is impossible without butchery, consider the paths you can take: down through a closet below, up into an attic, or around through a chase you create behind a new built-in.
Sometimes the smartest play is to leave one thing alone. If a vintage sconce location feels odd but moving it means tearing out a run of hand-finished tile the homeowner loves, I may change the sconce to a model that throws light where we need it rather than chase perfection on paper.
Safety devices that should not be optional
Local code will insist on some of these, but even where it does not, I install them:
- GFCI protection on all bathroom receptacles, by breaker or device, with any downstream loads properly labeled and tested. A fan timer capable of at least 30 minutes, or a smart control tuned to the room’s real moisture. A combo AFCI/GFCI breaker where available and compatible, especially in remodels with mixed vintage wiring that benefitted from new splices. A deep device box for any smart switch or thermostat that needs more cubic inches, with pigtails sized and twisted properly rather than stuffed. Tamper-resistant receptacles, particularly in family homes, because small hands and metal hairpins remain a classic pairing.
The math you should actually do
Do not trust “should be fine.” A vanity with two GFCI receptacles on a 20-amp circuit, serving two adults who may run a 1500-watt dryer and a 400-watt iron simultaneously, sits close to the edge. The code might allow lighting and a fan on the same circuit in some jurisdictions, but the morning rush will not be amused when the lights die mid-curl.
Add the known wattages, round up, and leave at least 20 to 30 percent capacity on each circuit. LED lighting sips power, which invites laziness. Resist it. That 8-watt downlight may not move the needle, but the cumulative insult of heaters, fans, and gadgets will.
Box fill is not a suggestion. Each conductor counts, devices count, grounds count. A 14-cubic-inch box with five conductors, a device, and a ground is a frustration trap. Upsize boxes during rough-in. The materials cost pennies more. The labor savings when you set devices without a wrestling match is real.
Coordination with the tile and plumbing crews
Electricians and tile setters meet each other’s work in tight spaces. If you want a flush outlet in a tile backsplash or a sconce centered on a grout line, talk about it before anyone spreads thinset. I have nudged a box half an inch to keep a sconce off a tile seam that would have caught the eye forever. If your tile setter plans a thick mud bed, your box extension rings need to match, or you will find devices sunk in a shadowy well. Label every switch’s function with painter’s tape during rough-in. Ten white cables in an open stud bay look like possibilities today and annoyances tomorrow.
Heated floor thermostats beg for a clean wall segment. Avoid inside corners and outside corners where the wall plate never sits perfectly. If the designer wants symmetry, fight for it at rough. You cannot shim symmetry into place later.
Waterproofing and penetrations that do not become mold magnets
Every hole through a waterproofing layer is a liability unless you treat it right. A recessed shower light needs a gasket or an airtight trim. Seal around penetrations with the manufacturer’s approved sealant, not whatever caulk tube is lying in the bucket. If you or your electrician cuts through a Schluter-style membrane or a liquid-applied waterproof layer, patch it like the substrate depends on it, because it does.
I also seal the top edges of vanity outlet boxes with firestop or acoustical sealant in exterior walls to slow moist indoor air from pumping into cold cavities where it condenses. That tiny practice keeps frost off sheathing in cold climates and builds a quieter room.
Energy and comfort without the lifestyle lecture
Bathrooms are short-visit rooms with intense energy spikes. LED lighting and efficient fans bring the baseline down. The bigger wins come from smart control. A fan that runs past the shower keeps moisture from loading your drywall. A floor warmer on a schedule makes the space cozy in the morning without running all day. Occupancy sensors on low-level night lighting prevent the 2 a.m. light-blast that ruins your sleep.
If you live where electricity costs sting, those controls move the needle more than agonizing over a 7-watt versus 9-watt lamp. I have seen bathrooms where the fan never turned on because it was noisy, then watched paint peel and caulk grow black seams. Spending a bit more on a quiet fan saved Extra resources more than a decade of repainting.
Troubleshooting the top three post-renovation complaints
I keep a mental list of calls I hope not to get.
The lights dim or flicker when the fan or heater turns on. That usually means a shared neutral problem, a weak connection, or a mismatched dimmer and LED driver. The fix is not to buy a new bulb, it is to tighten every splice, separate circuits properly, and use a dimmer compatible with the exact fixture.
The GFCI trips randomly. Moisture in a box, a bootleg neutral downstream, or a poor-quality device shows up here. Start by isolating what is actually protected by the GFCI. Check for shared neutrals tied to other circuits and for condensation inside exterior-wall boxes in cold climates.
The heated floor does not heat evenly. Installation drives this more than electricity. Mats overlapped, sensors misplaced near a cold area, air gaps under tiles. The electrical piece is simple: correct supply voltage and a healthy resistance reading that matches the manufacturer’s spec. I meter the mat at rough-in and again before tile to catch a nail through a cable. Skipping that step turns a $200 fix into a $2,000 redo.
When to call an electrician, even if you are handy
If your plan touches the panel, adds a new circuit, or mixes old and new wiring methods in one box, bring in a licensed electrician. If you are in a multi-unit building, add another layer of caution. Party walls and shared chases create code and liability tangles that no YouTube video solves.
If your home dates to an era with aluminum branch wiring or a patchwork of DIY, do not guess. I have opened walls to find wire-nutted splices buried behind plaster, which is illegal and unsafe. Those turn into junction boxes with covers, not wishful thinking. A good electrician will not only wire what you want, they will quietly fix the sins of the past so your shiny renovation does not sit on a shaky foundation.
A quick pre-drywall check that saves headaches
Use this simple walk-through before the walls close:
- Flip every planned switch and name it out loud while someone at the panel labels the circuit. Verify the box depths against the final wall build-up, including tile and mud beds. Test GFCI and AFCI function at the device or breaker with a plug-in tester and a simulated load. Confirm that any low-voltage drivers and thermostat sensor leads are accessible, not buried. Turn on the exhaust fan with the duct temporarily terminated and feel for strong pull at the grille. If it wheezes now, it will underperform later. Fix the duct path while it is still easy. Check clearances: sconces align to mirror edges, shower trims land outside direct spray where required, and outlets sit where cords reach without draping over basins. Measure resistance on heated floor mats and log the value with date and photo. Tape the log inside the thermostat box for the future installer.
The payoffs of doing it right
When a bathroom’s electrical plan respects both code and human behavior, it disappears in the best way. You walk in and your hand finds the right switch. The fan spins up and the mirror stays clear. The glow at your feet keeps you sure on a sleepy midnight trip. A hair dryer does not black out the vanity. On paper those are small wins. In lived space, they add up.
Bathroom renovations ask you to knit glamour and grit. The tile will draw praise, but the circuits, the switch logic, the quiet whoosh of a properly ducted fan, and the warm floor under bare feet will decide whether you love the room a year later. Electricity is not the star of the show, but it is the stage crew that cues every scene. Treat it with that level of respect, plan it with room to breathe, and your bathroom will work as good as it looks.