LED lighting: the swap order that pays

KiloWise editorial team · Last updated 5 November 2026 · Category: Lighting & Appliances

Swapping a bulb for an LED is the simplest energy saving there is: unscrew one, screw in the other, done. But if your home still has a dozen old halogen or incandescent bulbs, the order you swap them in matters more than most people realise. A bulb that burns for five hours a day saves you far more than a bulb in a cupboard you open twice a week — even though both swaps cost the same.

This guide gives you a ranked swap order: which rooms first, what each swap is worth, and what to do with the old bulbs. It also covers the renter's version of the job, because bulbs are one of the few energy savings you can take with you when you move. There is a worked example below, priced in both US dollars and UK pounds, so you can see exactly what one bulb is worth and scale it to your whole home.

Why the swap order matters

Every bulb you swap saves electricity in proportion to two things: how many watts it saves, and how many hours it burns. The wattage saving is roughly the same for every bulb of the same type — a 60W halogen swapped for a 9W LED saves 51 watts wherever it sits. The hours are what differ. A living-room lamp that burns for five hours every evening saves far more in a year than a spare-room bulb that burns for twenty minutes a week.

That is why the order matters. If you swap the cupboard bulb first and the living-room bulb last, you have spent the same money and waited months longer for the saving that was always the biggest. Swap the most-used lights first and the payback starts immediately; swap the least-used last, or leave them until they burn out, and you lose nothing.

There is also a comfort argument for going first in the rooms you live in. The kitchen and the living room are where you will notice the light quality — and where a good LED earns its keep. If you are unsure whether you like LED light, start with one bulb in the room you use most. Live with it for a week. If you like it, carry on through the house in the order below.

Which bulbs to swap first

Rank your bulbs by hours of use, not by room size or by which bulb is easiest to reach. The table below is a typical order for a family home — your home will differ, so walk through it room by room and count the hours honestly. A bulb that is on from dark until bedtime outranks a bulb that is on for an hour after dinner, however grand the room.

Two practical points before you buy. First, match the fitting: check whether the bulb is a screw fitting or a bayonet fitting, and whether it is a standard shape or a spotlight. Bring the old bulb with you or photograph the fitting, and you will not come home with the wrong one. Second, match the brightness and the warmth. Brightness is measured in lumens, not watts — a 9W LED can give roughly the same light as a 60W halogen. Warmth is measured in kelvin: around 2700K is warm and yellowish like an old bulb, 4000K is cooler and whiter. If you want your rooms to feel the same as before, choose warm white at about 2700K.

One more thing: dimmer switches. If a light is on a dimmer, check that the LED you buy is marked dimmable. A non-dimmable LED on a dimmer can flicker or buzz, and the dimmer may not work properly. Dimmable LEDs cost a little more, but they are the right bulb for the job.

LED vs halogen vs incandescent

The old technologies turn most of their electricity into heat and only a small part into light. An LED does the opposite: it turns most of its electricity into light. That is the whole story, and it is why the wattage drops so sharply for the same brightness.

The worked example below uses a 60W halogen and a 9W LED because that is the most common swap in a home that was fitted out before LEDs became standard. If your old bulbs are incandescent, the comparison is essentially the same. If your old bulbs are already compact fluorescents, the saving from swapping to LED is smaller — but the LED still uses less power, gives light instantly, and contains no mercury.

LEDs also last far longer than halogen or incandescent bulbs in normal use, which is a second saving that does not show up in the electricity maths: you buy replacements far less often. The exact lifetime depends on the bulb and how it is used, so check the rated life on the box rather than assuming a number — and keep the receipt, because a good LED should outlast several halogen bulbs.

What to do with the old bulbs

Do not throw old bulbs away without checking your local rules first, because the rules differ by bulb type and by area.

Fluorescent tubes and compact fluorescent lamps (CFLs) contain a small amount of mercury, so most areas ask you not to put them in general waste. Look for a household recycling point or a retailer take-back scheme in your area — your local council or waste authority will list where to take them. If a fluorescent tube breaks, ventilate the room and sweep the pieces into a sealed bag rather than vacuuming, then check your local guidance for disposal.

Halogen and incandescent bulbs are a different case: in many areas they go in general waste, because they contain no mercury and are not recyclable in the usual way. But rules vary, so check your local council or waste authority's guidance before you bin them — some areas have separate collection points, and the rules change. LEDs that have failed can often be recycled as small electrical waste, again depending on your area.

Whatever you do, do not stockpile old bulbs in a drawer for years. Swap them out, dispose of them properly, and move on. And if you are a renter, keep the old bulbs you remove in a labelled box: you will want them again when you move out.

The renter's note: bulbs are yours to take with you

Changing a light bulb is one of the few energy savings that needs no landlord permission, and it is one of the few you can take with you when you leave. The bulbs you buy are your property. When you move out, refit the old bulbs you kept in the box, and take your LEDs to your next home — where they will start saving you money from the first evening.

Two small disciplines make this painless. First, keep the old bulbs: a labelled box in a cupboard costs nothing and saves an awkward conversation at the end of the tenancy. Second, note what you changed: a quick list of which rooms you swapped, so you can put everything back as you found it. Leave the property as you found it, and the LEDs you take with you are pure gain.

Renters have more options than bulbs alone. Our guide to energy saving tips for renters lists twelve fixes that need no landlord permission, including draught excluders you can take with you and thermostat settings that cost nothing to change.

Start with the kitchen

If you do one thing after reading this guide, swap the kitchen bulbs. They burn the longest, the saving starts tonight, and you will have proof within a month — not on your bill, which mixes everything together, but in the simple fact that the room is lit for a fraction of the power it used to take. Then work down the table: living room, hallway, bedrooms, and the rest when you get to them.

Lighting is one of the quick wins in a whole-home energy audit, and it pairs with the other free habit in the home: switching off standby power. Our guide to how much standby power costs shows which devices are worth switching off at the socket, and the standby power estimator will price your own home's standby draw.

Related: price your home's always-on devices with the standby power estimator, then read our guides on how much standby power costs and energy saving tips for renters.

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