Use the electrical input, not the cooling capacity
A unit sold as 2.5 kW cooling does not normally draw 2.5 kW of electricity. Cooling or heating capacity describes the heat moved; electrical input is the power purchased from your supplier. Use the model’s rated or seasonal input data when estimating cost.
Inverter systems also modulate. They may draw more while pulling a hot room toward the set point and then reduce input as the load settles. A single nameplate figure is therefore an estimate, not a promise of constant consumption.
A worked example you can replace
If the assumed average electrical input were 0.60 kW and electricity cost 25 pence per kWh, one hour would cost about 15 pence: 0.60 × £0.25. Four hours a day across 30 days would be about £18.
That is an arithmetic example, not a RyRow performance claim or a forecast for your property. Weather, room load, set point, cycling and the actual model can move the result in either direction. The calculator keeps every assumption visible so you can replace it.
What makes the system work harder
The system has to remove heat entering the room and heat produced inside it. Large sunny glazing, a loft roof, open doors, cooking, computers and exercise all add load. The difference between indoor and outdoor temperature also matters.
A system in a shaded bedroom may spend much of the night maintaining a small load; a glazed extension in afternoon sun may face a much larger peak. That is why the same model can have different running costs in two properties.
Settings that reduce waste without losing comfort
Choose a moderate set point and allow the room to settle. Setting the controller dramatically lower does not turn a fixed system into a faster machine; it can simply make it run longer and leave the space uncomfortable.
Close unnecessary openings, use blinds before strong sun reaches the glass, and schedule the system around occupancy. In a bedroom, pre-cooling before sleep followed by a quieter maintenance setting may be more comfortable than starting from a very hot room at bedtime.
Why sizing and position affect energy use
An undersized system may run at high output without reaching comfort. An oversized unit or a poor airflow position can create rapid cycling, temperature swings or a strong draught near one part of the room.
A useful survey considers the room load and air path together. Capacity should cover credible peak conditions while still allowing stable low-load operation. The goal is not the biggest unit available; it is controlled performance across the conditions the room actually experiences.
Cooling cost and heating cost are different questions
In heating mode the system is an air-to-air heat pump. Its performance changes with outdoor temperature and operating conditions, so a summer cooling estimate cannot be reused as a winter heating estimate.
For either mode, compare the seasonal efficiency data for the proposed model and ask which rooms the design is intended to serve. One indoor unit cannot reliably condition several closed bedrooms simply because its headline capacity is high.
Interactive estimate
Running-cost calculator
Use the proposed model’s electrical input—not its cooling capacity—and your own electricity rate. The result is arithmetic, not a performance guarantee.
Actual input varies as an inverter system responds to heat load, weather and set point. Ask for model-specific seasonal data before purchase.