Is this the room you are thinking of?
These are the rooms people call us about. What they have in common is that extending the central heating into them is expensive, disruptive, or simply not possible.
Freezing from November to March and unbearable in July, so it gets used for four months of the year. One unit fixes both ends of that, which is why it is the room we are asked about most.
Usually built with no connection to the house heating at all. A fan heater is the default answer and it is the most expensive way to heat anything.
Heat rises, so it bakes in summer and the single radiator up there struggles in winter. Extending the boiler circuit that far is rarely worth the disruption.
Adding radiators means opening floors and possibly a bigger boiler. A unit on the wall avoids the pipework entirely and cools the new space in summer as well.
Cold floor, cold walls, and always the coldest room in the house. Heating it properly by turning up the whole house is expensive and makes every other room too warm.
A spare room, a dining room, a workshop. Heating one room on demand costs a great deal less than firing the boiler for the entire house.
Keep one room cosy. Turn the rest of the house down.
You already know this trick. It is what people have always done with a fire in the lounge: warm the room you are actually in, and let the rest of the house sit cooler. The difference is that this does it at the flick of a switch, with no fuel to fetch and nothing to clean out in the morning.
Most of us heat the whole house to keep one or two rooms comfortable. Every empty bedroom, the hallway, the spare room nobody has opened since Christmas: all of it warmed through the evening so the living room feels right. Put a unit in the room you spend your evenings in, keep that one properly warm, and the thermostat for everywhere else can come down a few degrees.
October, November, March and April are the awkward ones: not cold enough to justify heating the house, too cold to sit still. One room, warmed on its own for the evening, covers those weeks without the boiler coming on at all.
A cooler bedroom is what most people prefer to sleep in anyway, and a hallway does not need to be 21 degrees for anybody's benefit. Comfort where you are, and only where you are.
The same unit that keeps you warm in January is what keeps the room bearable in July. Nothing else on your heating bill does both, which is a large part of why it is worth installing at all.
To be clear about where that saving comes from: it is because you stop paying to heat rooms nobody is in, not because one fuel is cheaper than the other. Heat less of the house, for fewer hours, and the bill follows.
What would it cost to run today?
Using today's real hourly forecast for Alvechurch, here's the estimated electricity cost of holding a room at your chosen temperature, hour by hour. Pick your room size, set the target, and switch between heating, cooling and both.
Or drag the two green markers on the axis to set your own hours.
Today's forecast for Alvechurch: high of 17°C around 2pm, low of 12°C around 11pm.
How we work this out
This is an illustration, not a quote. We take today's real hourly outdoor temperature for Alvechurch and estimate the electricity a modern inverter unit would use to hold a room of your chosen size (small up to about 20 m², medium 20 to 30 m², large 30 m² and up) at your target, cooling when it's warmer outside and heating when it's cooler. We assume a unit that delivers roughly 3.5 to 4 units of comfort per unit of electricity, priced at today's electricity rate of about 25.3p per kWh (we refresh this daily from Octopus; your own tariff may be higher or lower). Warming a cold room up or cooling a hot one down from scratch costs a little more at first; steady holding is gentler. Your real figures depend on your room, unit, tariff and how you use it. See how it works and what it costs for the full picture, and we'll confirm the exact sizing and your fixed price at a site visit before we install.
Why it beats a plug-in heater, and it is not close
A fan heater, an oil-filled radiator and an electric panel heater all do the same thing: they turn electricity into heat, one for one. Put a kilowatt in, get a kilowatt out. That is the ceiling for all of them, and none can beat it.
Air conditioning does something different. It does not make heat, it moves heat that is already outside into your room, and moving is much cheaper than making. For every kilowatt of electricity it draws it delivers roughly three to four kilowatts of heat into the room. On the same electricity meter, at the same unit rate.
| Fan heater | 1 kW of heat |
| Oil-filled radiator | 1 kW of heat |
| Electric panel heater | 1 kW of heat |
| Air conditioning, in heating mode | 3 to 4 kW of heat |
A guide, not a promise. How much you get depends on how cold it is outside, how well the room holds heat and how warm you like it. The figures fall in very cold weather, and even at their worst they stay well ahead of anything that plugs into a socket.
And against the boiler, on carbon
This is not about replacing your central heating. It is about the room the central heating does not serve, and about the shoulder months when firing the whole house for one cold room makes very little sense. Here is how a year of heating compares on carbon.
Your heating carbon across the year
Because it moves heat instead of burning fuel, air conditioning puts out far less carbon than a gas boiler, every month of the year. The shaded gap is the carbon you would save. Set the room size and temperature to see it.
How we work this out
This is an illustration, not a quote. It estimates the carbon from heating one room across a typical UK year, using average monthly outdoor temperatures and standard heating degree days, so the amount of heating naturally rises in winter and falls to almost nothing in summer. We assume the unit's efficiency changes with the weather (around 3.3 units of heat per unit of electricity in midwinter, rising above 4 in milder months), on grid electricity at roughly 0.20 kg CO₂ per kWh, a UK average that keeps falling as more wind and solar come online. The gas figure assumes a boiler about 90% efficient at around 0.18 kg CO₂ per kWh of gas burned. It compares heating only, since a gas boiler cannot cool. Your real figures depend on your home, your unit, the weather and how you use it, so treat this as a guide. We'll confirm the exact figures for your property at a site visit before we install.
What we would rather tell you now
There is no getting round that. It is an installation with an outdoor unit, a hole through the wall and pipework, not something you carry home. What it buys you is a room that is comfortable all year and running costs that are a fraction of the alternative, so it pays back over years rather than months.
It needs a wall or a base outside with room for air to move around it. Most homes have somewhere sensible. Some do not, and if yours is one of them we will say so rather than talk you into a compromise you will regret every time you look at it.
It is very good at one room, or a few rooms, done properly. Heating an entire house this way is a different job with a different price, and it is not what this page is about.
Efficiency falls as the outside air gets colder, so a January night is its least impressive moment. It still delivers well over twice the heat you would get from a plug-in heater at that point, which is the comparison that matters.
Find out what your room would cost
Answer a few questions about the room and you will get a price on screen. No phone call, no visit, no obligation.
Get an online quoteWant to know why moving heat beats making it? Read the science of air conditioning.