Lighting a house you are not in

Put a dusk-to-dawn bulb in the porch fixture and you have done the most useful thing available, permanently, with no schedule to set and nothing that can lose its network. Then put one or two interior lamps on an evening schedule - a photocell timer or a smart plug, depending on whether you want to be able to change it from away. Skip randomized vacation mode entirely.

Most advice on this subject is written as if the job were to convincingly impersonate a household. It is not, and attempts to do it are what produce the lamp flicking on at 3:12am. The actual job is narrower and much easier: a house should not look conspicuously unattended, and the main way houses look unattended is an entrance that stays dark every night for a week.

That reframing changes the shopping list. You are not buying cleverness. You are buying something that will still be doing the right thing on day nine, with nobody there to notice it has stopped.

Every one of these devices works on the bench. What separates them is what happens on the fourth day, when you are not there and something goes wrong.

A photocell has nothing to fail. It is a sensor that notices it has got dark. No clock to drift, no schedule to be wrong, no account, no firmware. It cannot be reconfigured from away, and it does not need to be.

A plug-in timer fails only to a power cut, and the better ones keep their settings through one. A clock timer will be out by whatever the outage lasted; a photocell one will not notice.

A smart plug has the longest chain. It needs your Wi-Fi, which needs your router, which frequently needs an internet connection to reach the app. Most of them run their stored schedule locally if the cloud goes away - but "most of them" is doing real work in that sentence, and the one thing you cannot do from a thousand miles away is power-cycle a router. In exchange you get the ability to change your mind, which is genuinely useful if a trip runs long.

An in-wall astronomic timer fails least of all, because it works out sunrise and sunset from the date and your location and does not consult anything. It is also the only option here that is electrical work.

The instinct is to light everything. Resist it - the result costs more, looks less normal, and takes longer to set up.

• The entrance, from dusk. This is the one that matters and the one a dusk-to-dawn bulb solves permanently. An unlit porch every night for a week is the actual signal.
• One or two interior rooms, in the evening. A living room lamp or a landing light, on from dusk until a normal bedtime. Two sources at different heights look far more ordinary from the street than one ceiling light.
• Nothing overnight, inside. A bedroom lit at 4am every night for a fortnight is more conspicuous than a dark one, not less.
• Nothing you would not normally run. If the kitchen is never lit at 11pm when you are home, lighting it at 11pm while you are away is not an improvement.

Two lamps and a porch light is the whole plan for most houses. If you want the general version of the evening-lighting question rather than the away version, it is in layered lighting.

Four devices covering four different situations. The first one is the single most useful purchase here and the cheapest to live with, because once it is in you never think about it again.

Philips dusk-to-dawn A19 - the pick, and the one to buy first. A standard bulb with a light sensor built in: it switches itself on at dusk and off at dawn, every night, forever, with no schedule and no network. 800 lumens at a soft white color temperature, and flicker-free is stated on the listing.
Who it is for: anybody with a porch fixture, whether or not they travel. Who should skip it: anyone whose porch fixture is on a switch that gets turned off - the bulb needs constant power to sense anything.
Cons: the sensor needs to see ambient light, so a deep enclosed lantern can confuse it; you cannot override it from indoors without cutting power; and it runs all night, every night, which is the point but is also a running cost.

BN-LINK outdoor photocell timer - for plug-in lights, with nothing to configure. Two weatherproof outlets on a photocell: on at dusk, off at dawn or after 2, 4, 6 or 8 hours. It is ETL listed and rated 15A resistive, and it is the cheapest thing on this page.
Who it is for: outdoor plug-in lights - string lights, a landscape run, a lamp on a covered porch. Who should skip it: anyone who wants to change the schedule once they have left.
Cons: the tungsten rating is only 5A; both outlets switch together; it has to hang at least a foot off the ground to stay weatherproof; and the countdown is fixed steps rather than a real schedule.

Kasa EP25 smart plug - the only one you can change from away. A mini smart plug supporting Apple HomeKit, Siri, Alexa and Google Home, with schedules in the app. If a trip runs long or you want the living room lamp on an hour earlier, this is the one that lets you do it from an airport.
Who it is for: interior lamps, and anyone who wants remote control rather than set-and-forget. Who should skip it: a house with unreliable Wi-Fi, where the device with the longest dependency chain is the wrong choice.
Cons: depends on your network staying up while you are not there to fix it; one more account and app; and it is a plug, so it only controls what is plugged into it.

Intermatic ST01K astronomic in-wall timer - the permanent answer for a hardwired porch light. It replaces the wall switch and works out sunrise and sunset from the date, including daylight saving, so it stays correct for the whole trip and the whole year. It needs no neutral wire and keeps its settings through a power cut.
Who it is for: owners with a hardwired entry light and no plug to use. Who should skip it: renters, and anyone who does not want to open a switch box.
Cons: electrical work, so permission and usually an electrician; the wall plate is sold separately; no app or voice control; and it is the most expensive option here by a distance.

The default move - flip a couple of lamps on and leave them - has a price, and it is worth seeing it before a two-week trip.

Set it a week early and watch it run. This is the single most useful habit here. A schedule you tested on a normal evening is a schedule you know works; a schedule you set at midnight while packing is a guess.

Check what the device does with no internet. For anything smart, unplug the router for ten minutes and see whether the lamp still switches on schedule. If it does not, it is the wrong device for a trip.

Leave the wall switch alone. A dusk-to-dawn bulb, a plug-in timer and a smart plug all need constant power at the fixture or outlet. Any of them is defeated by somebody turning the switch off on the way out of the door - including you. Tape is not beneath anyone's dignity here.

Point the photocell at the sky, not at the lamp. A sensor that can see the light it controls will hunt on and off all evening. Same rule for a dusk-to-dawn bulb in a deep lantern - see motion sensors vs dusk to dawn for how each sensor type behaves.

Tell whoever has the key. If a neighbor is checking the house, a light that switches itself is only confusing if nobody mentioned it.