Economy 7 is a cheap night tariff. The lower unit rate applies for a set overnight window, and the daytime rate is often higher than a single-rate deal. Cooling is mostly a daytime load, because that is when rooms overheat. Economy 7 rarely makes air conditioning cheap.
The Economy 7 window is overnight
The cheap window is overnight, commonly seven hours, and the times sit on your tariff not on the air conditioner. Afternoon sun, cooking and people home from work all sit outside that window. The kilowatt-hours the split uses then are billed at the day rate.
Daytime heat meets the day rate
Cooling follows the heat, which is mostly by day, so the day rate is often the one that matters. Ask the installer for electrical input in kilowatts, not only cooling capacity. Multiply by the hours you expect, then by the day rate on your bill for afternoon use and the night rate only for hours inside the cheap window.
Changing tariff just to cool
A higher day rate can make other daytime electricity dearer as well. Moving onto Economy 7 only to run cooling can raise the rest of the bill. Read the day rate and the night rate together before you treat the night figure as the cost of comfort. Your own bill is the price list. This page is not a tariff.
Frequently asked questions
Does Economy 7 make air conditioning cheap?
Rarely. Economy 7 is a cheap night tariff, and cooling is mostly a daytime load. You usually pay the higher day rate for the hours the room is hot.
Should I cool the house overnight on the cheap rate?
You can run it then, and a bedroom may use some night units. A typical UK home then warms through the glazing and the walls, so you still cool in the afternoon at the day rate. Bedrooms that run all night also catch sleep and noise.
Is the price cap my Economy 7 rate?
No. Use the day and night rates printed on your bill. Ofgem's price cap is a household benchmark. Your Economy 7 rates can differ from it.
Does early-morning heating sit on the night rate?
Heating mode in the early morning can overlap the tail of the night rate for a short time. That does not turn Economy 7 into a cooling tariff. Energy Saving Trust treats these machines as air-to-air heat pumps: they use electricity whenever they run.
Does a choked filter change which rate I pay?
A serviceable filter and a clear outdoor coil keep the run time nearer the estimate. A choked unit runs longer at whichever rate is in force. It does not move afternoon cooling onto the night rate.
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How this guide was prepared
This guide was written by the Local AC Installers Editorial Team. We compare official guidance, legislation and established consumer information, separate general information from project-specific advice, and show publication dates and sources. We do not accept installer accreditation claims at face value.