Only partly. Economy 7 gives you seven hours of cheaper electricity, but those hours fall in the middle of the night, and most homes need cooling on summer afternoons and evenings, when you pay the higher day rate. An air conditioner will run happily on an Economy 7 meter. It just will not use the cheap rate unless you run it between roughly midnight and 7am, which in practice means bedroom cooling. Whether the tariff is worth it for you depends on how much of your total electricity use falls in the cheap window.
This guide explains how the tariff works, where air conditioning fits, a worked running-cost example you can repeat with your own rates, and the practical limits of trying to cool a house "on the cheap".
TL;DR
- Air conditioning works on Economy 7, but it only gets the cheap rate if it runs during the off-peak window, usually overnight.
- Most UK cooling demand is on hot afternoons and evenings, so most of your usage will be charged at the dearer day rate.
- Overnight bedroom cooling is the best fit for the cheap window. Cooling a whole house in advance is far less effective.
- To check the cost, multiply the unit's kW draw by hours run and your actual day or night rate in pence per kWh.
- Moving to Economy 7 just for air conditioning rarely pays off, because every other use in the house is charged at the higher day rate too.
Table of Contents
- How Economy 7 works
- Can air conditioning use Economy 7 off-peak electricity?
- Is it cheaper to run air conditioning overnight or in the day?
- How much electricity does home air conditioning use?
- Work out your own Economy 7 cost
- The limits of overnight cooling
- Which system suits Economy 7 households?
- Our perspective: James on Economy 7 and cooling
- Planning an installation
- FAQ
- Sources
How Economy 7 works
Economy 7 is a two-rate electricity tariff. According to the Centre for Sustainable Energy, cheaper electricity normally runs from midnight to 7am in winter and 1am to 8am in summer, though exact times can vary between suppliers. The other 17 hours cost more than a normal single-rate tariff.
That last point is the one people miss. The cheap night rate is paid for with a dearer day rate. If most of your electricity is used during the day, Economy 7 can cost you more than a standard tariff, not less. It was designed for homes with electric storage heaters or a hot water cylinder that charges overnight, where a large share of consumption can be shifted into the cheap seven hours.
The meter and the switch-off of the old timing signal
Many older Economy 7 meters were switched between rates by a radio signal. Radio teleswitch meters (RTS) lost that signal when the service was switched off, and the Energy Saving Trust says households with an RTS meter should contact their supplier to arrange a replacement, usually a free smart meter. If a smart meter cannot be fitted, the supplier must provide a suitable alternative. If your cheap-rate times look odd, or your meter is old, ask your supplier to confirm your off-peak hours in writing before you plan anything around them.
What the rates look like
Your two rates are on your bill and in your supplier's account page, quoted in pence per kWh. For context, the average electricity rate under the energy price cap for standard variable tariffs paid by Direct Debit is 26.32p per kWh from 1 October to 31 December 2026. The cap changes every quarter, so treat that figure as a reference point and use your own tariff for any calculation. Economy 7 night rates sit well below it, and day rates sit above the single-rate figure.
Can air conditioning use Economy 7 off-peak electricity?
Yes, with one condition: the unit has to be running during the cheap window. Economy 7 does not recognise appliances. The meter simply records what passes through it, and charges the night rate to anything drawn between the off-peak hours. There is nothing to wire in or configure on the air conditioner itself.
Two practical points follow.
- Your timer is your tool. Modern split systems have a built-in on/off timer, so you can set the unit to start or stop at set times. That is how you make sure it runs in the cheap period and stops when the dear rate begins.
- Everything else in the house is still on the same tariff. The kettle, oven, laptops and the air conditioner you switch on at 4pm all pay the day rate.
If your home already has storage heaters, an electric immersion heater or an electric vehicle charging overnight, you may already be on Economy 7. Adding a split system to that household means you can use the cheap hours for bedroom cooling without changing anything else.
Is it cheaper to run air conditioning overnight or in the day?
Per kWh, overnight is cheaper on Economy 7. The catch is that you rarely need the same amount of cooling at 3am as at 3pm.
A few things work in your favour at night:
- Outdoor air is cooler, so the system does not work as hard to hold a set temperature.
- A bedroom is a small space, so the unit often runs at low output.
- You are paying the lowest rate on your meter.
And a few work against you in the day:
- Solar heat gain through windows and roofs is at its highest.
- Appliances, cooking and people all add heat.
- Every kWh costs the higher day rate.
So the honest answer: a bedroom on a warm night is the ideal Economy 7 use, while cooling a living room at 5pm is the most expensive way to run the same machine.
How much electricity does home air conditioning use?
Power draw depends on the unit and how hard it is working. ClearScore's guide puts a modern wall-mounted unit at roughly 0.5 to 0.8 kW per hour, with portable units usually drawing 0.8 to 1.5 kWh. Insulation, sunlight, curtains, heat-producing appliances and air escaping the room all push consumption up or down.
Uswitch's running cost guide calculates hourly costs of between £0.20 and £1.32 across the unit types it lists, based on 26.32p per kWh. Larger units use more electricity, and your bill also depends on how long you run them and your tariff.
Efficiency matters as much as size. Units are rated by the Energy Efficiency Ratio (EER), where a higher rating means a more efficient unit. Over a long life, an efficient inverter split system costs noticeably less to run than a cheap portable unit doing the same job. We go into this in our guide to why energy efficient cooling pays back.
Work out your own Economy 7 cost
The formula is simple:
kW draw × hours run × rate in pounds per kWh = cost
Look up your rates first. Your bill or supplier account shows a day rate and a night rate in pence per kWh. The figures below are invented round numbers to show the method, not real tariff rates. Replace them with yours.
A worked example
Say a bedroom split unit draws 0.6 kW on average (within the 0.5 to 0.8 kW range above), and imagine a night rate of 15p and a day rate of 30p per kWh.
| Scenario | Hours | kWh used | Rate (illustrative) | Cost |
|---|---|---|---|---|
| Bedroom, overnight in the cheap window | 6 | 3.6 | 15p | £0.54 |
| Same unit, evening in the dear period | 6 | 3.6 | 30p | £1.08 |
| Living room unit at 0.8 kW, afternoon | 4 | 3.2 | 30p | £0.96 |
The same machine costs half as much overnight in this example, purely because of the rate. That gap is the full extent of the Economy 7 benefit for air conditioning. It does not make the unit cheaper in the afternoon.
Check the bigger picture before switching tariff
Do not switch to Economy 7 just to cool a bedroom. Add up your annual electricity use and estimate what share could genuinely move into the cheap hours. If it is a small share, the dearer day rate on everything else will probably outweigh the saving. If you already have storage heating or overnight charging, the maths is already in your favour and air conditioning on a timer is a bonus.
If you are comparing your usage against typical running costs, our piece on whether air conditioning is expensive gives the wider budget picture.
The limits of overnight cooling
The idea that appeals to many people on Economy 7 is to run the air conditioner in the cheap hours, "bank" the cool, then switch it off when the day rate starts. It is worth being realistic about this.
Air conditioning does not store cold. Unlike a storage heater, which holds heat in bricks and releases it through the day, a split system cools the air and the surfaces it touches. Once the unit stops, the room warms back up as heat arrives through walls, roofs and windows. A well-insulated, shaded home holds temperature for longer. A top-floor flat with a south-facing window will not.
Pre-cooling helps only a little. Running the unit from 1am to 8am and then closing blinds and windows can take the edge off a morning. By mid-afternoon on a really hot day the benefit is mostly gone, and you will want the unit back on at the day rate.
Cooling fabric costs energy. Dropping a room several degrees below what you need, to make it last longer, uses more electricity and can feel uncomfortably cold in the small hours. Setting a sensible target temperature is usually better than chasing a deep chill.
Noise and sleep. Overnight use needs a quiet indoor unit and a sleep or night mode that gradually raises the set temperature. Position the unit so the airflow does not blow directly onto the bed.
Windows, blinds and insulation do the heavy lifting. Shading windows during the day, closing curtains on the sunny side and keeping heat-producing appliances off all reduce the load before the air conditioner comes into play. Our guide to boosting air conditioning efficiency at home covers these steps in detail.
When Economy 7 and air conditioning do fit together
- A bedroom unit on a timer for warm nights.
- A home office or loft room used in the early morning, before 7am or 8am.
- A household that already uses storage heaters or overnight immersion heating and has an Economy 7 meter in place.
- A multi-room system where you only run the bedroom zone overnight. Our explainer on multi-room systems shows how zoning works.
When it does not
- A living room used and cooled mainly in the afternoon and evening.
- A home with no other electric heating, where Economy 7 would raise the cost of everything else.
- Properties that need all-day cooling, where the day rate dominates your bill.
Which system suits Economy 7 households?
If you plan to run overnight, choose for low noise and low part-load efficiency, not maximum cooling power. An oversized unit cycles on and off and wastes energy, while a correctly sized inverter split runs steadily at low output, which is exactly what bedroom use needs.
For a single room, a single-room mini split is usually the sensible choice. For several rooms, compare the options in our guide to types of air conditioning for UK homes. The advantages of split systems over portables are significant for overnight running: quieter, more efficient and no hose through a window.
As for upfront cost, ClearScore reports that professional installation of a single-room split system in the UK typically ranges from £1,750 to £3,000, including the unit and labour. A survey of your home gives a firm figure, since pipe runs, wall type and electrical work all change the price.
Our perspective: James on Economy 7 and cooling
We fit systems across Exeter, Devon and Cornwall, and the Economy 7 question comes up often from homes with storage heaters. Our view is plain: Economy 7 is a bonus for bedroom cooling, not a reason to buy or a reason to switch tariff.
The homes that get the most from it have a well-sized inverter unit in the bedroom, a timer set to match their off-peak hours, and blinds that keep the sun out during the day. The homes that are disappointed expected the system to cool the whole house for free overnight and stay cold until evening. That is not how air conditioning works.
In the South West, most of our domestic customers need cooling on only the warmest days, which makes system efficiency and sensible use more important than clever tariff tricks. We would rather size a system correctly and tell you what it is likely to cost to run than sell you something larger. Our engineers are F-Gas certified and REFCOM registered, we complete installations typically within one to two days, and we use our own engineers rather than subcontractors.
— James
Planning an installation
If you are considering a system and want to know how it will fit your tariff, we offer free surveys across Devon, Cornwall and the wider South West. We install Samsung, Mitsubishi, Toshiba and Daikin systems, and 0% finance is available. See our domestic installation service or book a survey. Once you are running, our service and maintenance plans keep filters and coils clean, which directly affects efficiency and running cost.
FAQ
Can I run air conditioning on an Economy 7 meter?
Yes. The meter charges whatever you draw at the rate for that time of day, so the air conditioner needs no special setup. You only get the cheaper rate if the unit is running during your off-peak window, so use its timer.
What are the Economy 7 hours?
According to the Centre for Sustainable Energy, cheap electricity normally runs from midnight to 7am in winter and 1am to 8am in summer, though times vary between suppliers. Check your own hours with your supplier, particularly if you have an older meter.
Is Economy 7 worth it if I only want air conditioning?
Usually not. The tariff gives you a dearer day rate for the other 17 hours, and most cooling is needed in the afternoon and evening. It makes sense when much of your household electricity, such as storage heating or overnight charging, already falls in the cheap window.
How much does it cost to run an air conditioner overnight?
Multiply the unit's draw in kW by the hours run and your night rate. A modern wall-mounted unit typically draws 0.5 to 0.8 kW, so six hours is about 3 to 5 kWh. At your own night rate, that gives a cost per night.
Sources
- Economy 7, Centre for Sustainable Energy
- RTS meter switch off, Energy Saving Trust
- Ofgem announces energy price cap increase from October 2026, LexisNexis
- Air conditioning cost, ClearScore
- Is air conditioning worth it in the UK, Uswitch
- Air Conditioning Buying Guide UK, Guides4Homeowners