Air Conditioning in Winter: How to Use It, Maintain It & Save Money
Yes—air conditioning can be very useful in winter. If you run a reverse-cycle system (heat pump), it can heat, dehumidify, and improve indoor air quality while using less energy than many traditional heaters. This guide from Clear Skies Energy explains winter operation, the best settings, maintenance essentials, common issues, commercial considerations, and FAQs—plus when to book a professional service.
Can you use air conditioning in winter?
Absolutely. Most modern air conditioners are reverse-cycle, meaning they can both cool and heat. In heating mode, they work like air-source heat pumps, extracting heat energy from the outdoor air and transferring it indoors. Even in cold conditions there is usable heat available, and well-specified systems remain efficient in the UK climate.
If your unit is cooling-only, you can still use dry/dehumidify or fan modes to manage condensation and circulate air, but you’ll need a separate heat source. If comfort and running costs matter, consider a heat-pump upgrade.
How heat pumps warm your home
- Heat transfer, not heat creation: The outdoor coil absorbs heat; the indoor coil releases it to your rooms. This transfer is why heat pumps can be so efficient.
- Coefficient of Performance (COP): In typical UK winter conditions, modern systems often deliver multiple kilowatt-hours of heat for each kWh of electricity used (performance varies by temperature and model).
- Defrost cycles: In near-freezing weather, frost can build on the outdoor coil. Your unit will occasionally run a short defrost cycle—normal behaviour that preserves performance.
- Low-ambient features: Cold-climate models may include crankcase and base-pan heaters and advanced controls for reliable operation in sub-zero temperatures.
Benefits beyond heating
- Condensation & mould control: Strategic use of dry mode reduces window condensation and helps prevent mould growth in poorly ventilated spaces.
- Cleaner indoor air: Filters capture dust and allergens that build up when homes are more sealed in winter.
- Zonal comfort: Multi-split and ducted systems let you warm rooms in use while saving energy elsewhere.
Best winter settings & modes
- Choose “Heat” mode (not “Auto”): This avoids unintended switching to cooling during mild midday periods.
- Set 19–21 °C for living spaces: A steady, moderate setpoint is usually more efficient—and more comfortable—than frequent changes.
- Fan speed on Auto or Low–Medium: Helps maintain quiet operation and stable temperature/humidity.
- Schedule wisely: Pre-warm rooms before occupancy, reduce output when you’re out or asleep.
- Airflow direction: Angle vanes slightly downward so warm air spreads evenly and avoids stratification at ceiling level.
Essential winter maintenance
Cold-weather reliability starts with basic upkeep. We recommend a seasonal service before the coldest months to protect efficiency and extend system life.
DIY checks you can do now
- Filters: Clean or replace monthly in heavy use. Blocked filters reduce airflow and raise running costs.
- Outdoor clearance: Keep at least 300 mm clear around the outdoor unit; remove leaves, debris, and snow.
- Condensate drainage: Confirm indoor and outdoor drains are clear to prevent leaks or ice build-up.
- Seals & draughts: Reduce heat loss by sealing gaps around windows and doors; close unused trickle vents.
What’s included in a Clear Skies Energy winter service
- Operational test, electrical safety checks, and controls calibration
- Refrigerant circuit inspection and leak checks
- Defrost cycle verification and low-ambient configuration (where applicable)
- Coil clean, airflow measurement, and filter replacement options
- Advice on zoning, schedules, and efficiency upgrades
Common winter issues & easy fixes
- Unit pauses or emits cool air briefly: Likely a defrost cycle; allow it to complete. Frequent cycles may indicate blocked airflow or poor siting—book an inspection.
- Outdoor unit noisy: Check for debris, ice contact, or loose panels. Persistent noise should be assessed by a technician.
- Room won’t reach set temperature: Filters may be dirty, doors/windows draughty, or the setpoint is too high for conditions. Try 20 °C, close internal doors, and ensure vents aren’t obstructed.
- Higher bills than expected: Review schedules, setpoints, and insulation. A service can recalibrate and suggest improvements.
7 practical efficiency tips
- Hold a steady setpoint: Avoid yo-yo temperature changes.
- Use zoning: Heat occupied rooms; reduce output in unused areas.
- Seal & insulate: Small draught fixes can yield big savings.
- Mind furniture placement: Keep returns and supply grilles clear.
- Leverage timers: Start a little early on cold mornings; scale back overnight.
- Keep coils and filters clean: Airflow is everything for efficiency.
- Consider smart controls: Automations and occupancy sensing can trim wasted runtime.
Commercial & office guidance
- Ventilation balance: Maintain fresh-air rates while avoiding cold draughts—consider demand-controlled ventilation.
- BMS & scheduling: Align setpoints with occupancy and business hours; avoid weekend/holiday drift.
- Indoor air quality: Upgrade to higher-grade filters where feasible and maintain regular changes to protect staff comfort.
- Asset protection: Planned winter maintenance reduces breakdowns, protects warranties, and stabilises energy spend.
FAQs
Is it cheaper to run a heat pump than electric heaters?
Typically yes. Because heat pumps move heat rather than create it, they can deliver several units of heat for each unit of electricity, reducing running costs—especially in well-insulated homes.
Should I use Auto mode in winter?
We recommend Heat mode to avoid the system switching to cooling during milder periods.
Why does my outdoor unit steam or pause?
That’s the defrost cycle clearing frost from the coil. It’s normal and helps maintain performance.
What winter setpoint is best?
Most households find 19–21 °C comfortable and efficient. Try 20 °C as a baseline and adjust slightly for preference.
Do I need a winter service every year?
Annual servicing is advisable for performance, safety, warranty compliance, and lower running costs.
Book a winter AC health check
Keep your system efficient, reliable, and comfortable through the cold months. Clear Skies Energy offers expert servicing, diagnostics, and upgrades for homes and businesses.
Prefer to speak to a specialist? Call our team or send a message—we’ll recommend the right service for your system and budget.
About Clear Skies Energy: We help households and businesses heat and cool efficiently with modern heat pumps, split and multi-split systems, and expert maintenance. If you’re considering an upgrade, ask about our design and installation options.





