What infrared heater power do I need for a garage, terrace or workshop
What power infrared heater do I need for a garage, terrace or workshop?
This is probably the most practical question a customer asks before buying an infrared heater. And also a question that is most often answered too simplistically – with the blanket rule "50 W per square meter", which actually applies only under very specific conditions. In practice, it's not that simple. A garage with a wooden door and an uninsulated roof behaves completely differently than a brick workshop with insulated walls. A terrace in the High Tatras needs a different power than an atrium terrace in Bratislava protected on three sides.
In this article, we'll go through the entire process of calculating the required power step by step – for each of the three most common use cases. You'll find specific figures, tables, practical examples, and an overview of mistakes people make when choosing. If you want to understand the deeper differences between types of infrared heaters, I recommend the article Short-wave vs. medium-wave vs. dark infrared heaters – which type is right for you, where this topic is discussed from a different angle.
Why "watts per square meter" alone isn't enough
The classic heating power calculation for convection heating is based on the volume of air, heat losses through walls, windows and roof, and the required temperature difference between indoors and outdoors. However, infrared heaters don't work primarily by heating air – they work through direct radiation, which heats surfaces and objects, not the air itself. This is the key difference that changes the entire calculation approach.
An infrared heater in an unheated garage heats only the space directly beneath and around it. The air may remain cold, but a mechanic working under a car feels the warmth of the radiation on their body. That's why you can have minus five degrees in the garage and still feel pleasantly warm, if a properly sized and positioned infrared heater shines directly on the work zone. Different rules apply if you want to heat the entire garage to +15 °C instead – then the calculation approaches convection heating and you need significantly higher power or a combined system.
Variables that affect the actual power requirement:
- Degree of insulation of the space – from an open terrace (zero insulation) to an insulated brick workshop
- Ceiling height – the higher the ceiling, the more heat is "lost" upward, and the greater the power required
- Type of use – zonal heating vs. full space heating
- Outdoor temperature – the design should take into account the coldest days in the given location
- Wind exposure – critical for terraces and more open spaces
- Heater mounting height – directly affects the heat flux density in the work zone
- Number and size of openings – doors, windows, uninsulated walls
Infrared heater power for a garage – how to do it
Types of garages and their thermal behavior
From practical experience, I know that garages are probably the most diverse category. I encounter simple metal garages without any insulation, brick garages attached to a family house, spacious workshop garages for two to three cars, and professional car repair shops with a ceiling height of 4–5 meters. Each requires a different approach.
Uninsulated metal or wooden garage: This is the worst case for calculation. Heat losses are enormous, and metal has no thermal capacity or insulation. If you wanted to heat such a garage to +15 °C at an outdoor temperature of –10 °C, you would need power that would be economically pointless. The right strategy here is zonal heating – aim the infrared heater directly at the work area, not the entire space. For such a garage of 3 × 5 m with a work area, one infrared heater with a power of 1,500 – 2,000 W is enough if the goal is the comfort of the working person, not heating the whole space.
Uninsulated brick garage: Concrete and brick have much better thermal properties than metal, but without insulation the heat losses are still high. For a standard garage of 3 × 6 m (18 m²) with a ceiling height of 2.4 m, at an outdoor temperature of –10 °C and a desired indoor temperature of +10 °C, I recommend a total power of 2,000 – 3,000 W. If the garage has insulated walls and roof (at least 5 cm of mineral wool), you can go to the lower limit or even slightly below.
Insulated double garage or garage-workshop: For a space of 30–40 m² with insulation and a ceiling height of 2.5 m, the typical required power is 3,500 – 5,000 W. Here it makes sense to consider two smaller units instead of one large one – better heat distribution, and the option to turn on only one zone for shorter work sessions.
Practical power table for garages
| Garage type | Area | Target (zone) | Target (whole space) |
|---|---|---|---|
| Metal/wooden, uninsulated | 15–18 m² | 1,500 – 2,000 W | not recommended |
| Brick, uninsulated | 15–20 m² | 1,500 – 2,000 W | 2,500 – 3,500 W |
| Brick, insulated | 20–35 m² | 2,000 – 2,500 W | 3,000 – 4,500 W |
| Double garage/workshop, insulated | 35–60 m² | 2 × 1,500 – 2,000 W | 4,500 – 7,000 W |
Important note on the table: the "Target (whole space)" values are calculated with an outdoor design temperature of –15 °C and a desired indoor temperature of +10 °C. For warmer regions, you can reduce the power by 20–30%. High humidity, uninsulated metal walls, or an open door during work significantly increase the power required.
Ceiling height – an overlooked factor
Garages with high ceilings (more than 3 m) require special attention. An infrared heater mounted at a height of 4 m has a much larger "width" of irradiated area, but the heat flux density in the work zone decreases with the square of the distance. In practice, this means that doubling the mounting height reduces the intensity of the heat radiation to a quarter. For garage spaces with a ceiling height above 3.5 m, we therefore increase the power by 30–50% compared to the table values, or choose dark tube heaters, which are more suitable for greater mounting heights. You can find more on this topic in the article Mounting an infrared heater on a ceiling or wall – procedure and safety requirements.
Infrared heater power for a terrace – a completely different game
Why the terrace is the most demanding case
On a terrace, you're essentially "heating outdoors" – heat escapes in all directions, wind carries away thermal comfort, and every gust of air makes the situation worse. Infrared heating is basically the only sensible technology for outdoor heating, because it heats bodies and surfaces directly, not the air, which would immediately blow away. A convection heater would be completely useless on an open terrace.
Terraces vary greatly – some are practically enclosed on three sides plus a roof, others are completely open to the garden. This is probably the most important factor affecting the required power:
- Covered terrace enclosed on 3 sides: The best case. The roof captures reflected heat, and the side walls block the wind. A power of 80–120 W/m² of terrace area is realistic at outdoor temperatures down to –5 °C.
- Covered terrace, open (pergola with roof, no walls): The roof helps, but the sides are open. Power needs to be increased to 150–180 W/m².
- Completely open terrace, only a canopy: Here the heat losses are extreme. Infrared heaters here work only as local "heat islands" – the goal is to warm the people sitting directly beneath them, not the entire space. Power of 200–250 W/m² and higher, with real comfort depending more on placement than on power.
Calculation for a specific terrace example
Imagine a covered restaurant terrace 6 × 4 m = 24 m², protected on two sides by a brick wall, open on the other two sides. Operation during autumn months, average outdoor temperature 5–10 °C, occasionally mild frost. Desired comfort: guests should feel pleasant even in winter clothing.
Calculation: 24 m² × 150 W/m² = 3,600 W minimum. For such a terrace, I recommend 3–4 heaters of 1,000–1,500 W each, evenly distributed, rather than one large one. Reason: even distribution covers the entire seating area, while with one large heater, people at the edges will feel cold.
Another example: a private garden terrace 3 × 4 m = 12 m², partially covered by a pergola, without side walls. Use: autumn evenings down to about –3 °C outdoors. Here I recommend 2 heaters of 1,500 W = 3,000 W total, which represents 250 W/m². This is the upper limit of reasonable sizing, but justified for an open space.
Wind – the biggest enemy of thermal comfort on a terrace
Wind can ruin even a perfectly sized system. Every meter per second of wind reduces perceived thermal comfort by the equivalent of several degrees Celsius. Therefore, for terraces in exposed locations (hills, corner terraces in cities, coastal locations), it is necessary either to increase the power by a further 30–50%, or to address wind screens – glass panels, fabric curtains, hedges. Wind protection is in many cases a more effective investment than a bigger heater.
For a deeper look at the specifics of outdoor use, I recommend the article Infrared heaters for terraces and gardens – how to heat outdoors efficiently and safely and also Outdoor vs. indoor infrared heaters – what are the differences and what to consider.
Infrared heater power for a workshop – a space where details matter
What sets a workshop apart from an ordinary space
Workshops have several specifics that both complicate and simplify the choice of infrared heater. On one hand, they are generally better-insulated spaces than garages, with a solid structure and the possibility of insulation. On the other hand, there are safety requirements – if you work with flammable substances in the workshop (thinners, paints, gasoline), you must use heaters suitable for these conditions, or a completely different type of heating altogether. In practice, I've seen many cases where an infrared heater was installed in a workshop regardless of the presence of flammable materials – this is a serious safety risk.
For workshops without flammable materials, infrared heaters are an ideal solution. Heat is immediately present after switching on (unlike underfloor heating or panel convectors, which warm up slowly), electricity can be easily regulated with a thermostat or timer, and a ceiling-mounted heater doesn't get in the way while working.
Calculation for craft workshops
For a brick workshop 5 × 8 m = 40 m² with a ceiling height of 2.8 m, 5 cm insulation, and a design outdoor temperature of –12 °C, with a desired working temperature of +16 °C (a difference of 28 K):
Space volume: 40 m² × 2.8 m = 112 m³. Heat loss with this insulation and volume is approximately 60–80 W/m² of floor area. Required power: 40 × 70 = 2,800 W as a base value. Since this is a workshop with real work taking place (doors opening, people bringing in cold air masses), I recommend a 20% reserve: 2,800 × 1.2 = 3,360 W → we choose 3,500 W as the installed power.
For larger production and service workshops (100 m² and more), the recommended solution is dark tube infrared heaters suspended along the ceiling. These heaters have a power of 2,000–6,000 W per unit and, at a ceiling height of 4–6 m, are significantly more efficient than spot heaters. For these spaces, it is always better to have an individual project prepared.
h3>Safety distances in a workshopWorkshops tend to have more potential sources of problems: flammable materials, storage shelves, tools hanging on walls. Minimum safety distances for infrared heaters in a workshop:
- From flammable materials (wood, paper, textile): at least 80 cm in all directions, 120 cm recommended
- From stored liquids and oils: at least 150 cm; if the rays would have direct contact, it is better not to use an infrared heater at all
- From the work surface: at least 60 cm, optimally 90–150 cm depending on the heater's power
- From walls and ceiling (for ceiling mounting): according to the manufacturer, typically 15–30 cm from the ceiling
Step by step: procedure for calculating the required power
If you want to do your own calculation responsibly, here is a proven procedure I use during consultations with customers:
Step 1 – Measure the area: The basic area in square meters. For workshops and garages, it's simple – width × length. For terraces, include only the part where people will sit or stand, not the entire structure.
Step 2 – Determine the type and condition of insulation: Is the space insulated? How well? Do you have metal walls or concrete? What is the ceiling height? Is it indoors or outdoors?
Step 3 – Choose the basic W/m² coefficient:
- Insulated interior (workshop, garage room): 60–80 W/m²
- Inadequately insulated interior (uninsulated garage): 100–130 W/m²
- Covered exterior protected from wind (terrace, 3 sides): 100–150 W/m²
- Partially covered exterior (pergola, gazebo): 150–200 W/m²
- Completely open exterior: 200–300 W/m²
Step 4 – Correction coefficients:
- Ceiling height above 3 m: +20–40%
- Strong wind exposure in the location: +20–30%
- Metal/wooden structure without insulation: +30%
- Door that is opened during operation: +15–25%
- Altitude above 600 m: +10–20%
Step 5 – Final reserve: Always add a 15–20% reserve to the calculated power. The reason is simple: a heater running at 70–80% of its power has a longer lifespan, and a thermostat can keep the space within a comfortable range without extreme power spikes.
The most common mistakes when sizing infrared heater power
From experience, I know mistakes that people make repeatedly. The first and most common is underestimating heat losses – a customer buys a 1,500 W heater for a 30 m² uninsulated garage and then is surprised that it's not enough even in September. The second mistake is the opposite – buying an enormously oversized heater for a small space, where the heater then runs at 20% power, extending its lifespan, but the equipment is unnecessarily expensive.
The third mistake is ignoring ceiling height. I've seen a 2,000 W heater installed at a height of 5 m in a 15 m² space – thermal comfort at working height was minimal, because the radiation density at such a distance is too low. Solutions would be either two units at a lower height, or a dark tube heater with a reflector.
The fourth mistake: underestimating wind on a terrace. A customer buys a 1,000 W heater for a "slightly windy" terrace, and when September comes, they feel as if the heater weren't there at all. Wind is just as important as the heater's own power for outdoor use. Sometimes it's cheaper to invest in a wind screen than in a bigger heater.
The fifth mistake concerns choosing the wrong type of heater for a given space. Short-wave heaters with a radiant temperature of 2,000–2,500 K are suitable for direct, short-term heating (terrace, canopy). For long-term heating of more enclosed spaces (workshop, garage), medium-wave or dark heaters are more suitable, as they don't produce as intense a light and have greater thermal stability. This is discussed in more detail in the article How to choose an infrared heater – type, power and placement according to the space.
Comparison of energy consumption – what will an infrared heater cost me
Power is one thing, but customers are also interested in how much it will cost in electricity. Here is an approximate calculation for the most common scenarios at an electricity price of €0.20/kWh (this price changes, recalculate with your current tariff):
| Scenario | Power | Hours/day | Consumption/month | Cost/month |
|---|---|---|---|---|
| Small garage, zonal heating | 1,500 W | 3 h | 135 kWh | ~€27 |
| Larger garage, whole-space heating | 3,000 W | 4 h | 360 kWh | ~€72 |
| Restaurant terrace, evenings | 4,500 W | 5 h | 675 kWh | ~€135 |
| Workshop 40 m², working days | 3,500 W | 8 h | 560 kWh | ~€112 |
Important: actual consumption is lower than these figures suggest, because the thermostat regulates the heater so that it doesn't operate at 100% the entire time. In practice, you can expect the heater to actually run at full power only 40–70% of the stated hours, the rest being thermostatic regulation. Actual monthly consumption may therefore be 30–50% lower than the "paper" calculation.
For a more detailed comparison of electric vs. gas heating costs, see the article Electric vs. gas infrared heaters – comparison of costs and use.
Special cases and combined solutions
Garage also used as a workshop – a two-zone solution
A very practical solution for combining a garage and workshop in one space is installing two separately controlled heaters – one aimed at the parking/service zone, the other at the work table and work area. Each has its own thermostat or switch. When you're only working at the table, you turn on just the second heater. When working under a car, you turn on the first. This solution reduces electricity consumption and increases work comfort.
Terrace with a variable number of people
Restaurants and cafés often have the problem that on Friday evening the terrace is full, while on Monday afternoon only three people are sitting on it. The solution is to install several smaller heaters (e.g., 6 × 1,000 W) instead of three large ones (3 × 2,000 W), with each heater or pair of heaters controlled separately. Staff turn on only as many heaters as there are occupied tables. This is much more energy-efficient than switching the entire system on and off.
Workshop with intermittent operation
Hobbyists and craftsmen who go to the workshop only on weekends or in the evening should consider a solution with a programmable thermostat. The workshop can be preheated 30–60 minutes before arrival to a minimum working temperature. Without preheating, you'll be cold for the first half hour, even with a fully sized heater – concrete floors and walls need to absorb heat before the space feels pleasant. This aspect of the thermal mass of a space is commonly overlooked in power calculations.
Frequently Asked Questions (FAQ)
Is one infrared heater with 2,000 W power enough for a 3 × 5 m garage?
It depends on several factors. For an uninsulated brick garage aiming to maintain a working temperature of around +10 °C at an outdoor temperature down to –5 °C, 2,000 W is at the limit – it will suffice on mildly cold days, but won't be enough during hard frosts. If the garage is an uninsulated metal or wooden structure, 2,000 W only serves as zonal heating for the worker, not for heating the entire space. For more comfortable use, I recommend 2,500 – 3,000 W with a thermostat.
Can I put one 3,000 W heater on a terrace (4 × 3 m) instead of three 1,000 W ones?
You can, but the result won't be the same. One large heater creates a significant warm center directly beneath it and cold edges. Three smaller heaters evenly distributed across the terrace ceiling cover the entire seating area evenly – every guest feels similar warmth. For larger terraces, distributing several smaller units is always better. Moreover, with one large heater, you don't have the option of zone control.
How does mounting height affect the power I need?
Very significantly. The intensity of infrared radiation decreases with the square of the distance (the so-called inverse square law). A heater mounted at 3 m delivers only a fraction of the heat flux to the work zone at a height of 1 m compared to a heater at 2 m. Therefore, for spaces with a ceiling height above 3 m, the power needs to be increased by 30–50%, or a dark tube heater should be chosen, which is structurally designed for greater mounting heights. You can find more on mounting requirements in the article Mounting an infrared heater on a ceiling or wall – procedure and safety requirements.
Is it better to have one powerful heater or several weaker ones?
For most applications, several smaller units are more advantageous. Reasons: more even area coverage, the option of zonal control, safety (if one fails, the others still work), better heat distribution without "hot" and "cold" spots. The exception is very small spaces (up to 10 m²), where one heater is sufficient and more would only unnecessarily complicate installation.
How many kW do I need for a restaurant terrace of 8 × 5 m?
For a 40 m² restaurant terrace, partially covered and protected on two sides, for operation down to temperatures around 0 °C, I recommend a total installed power of 5,000 – 7,000 W. In practice, this means 5–7 heaters of 1,000 W or 4–5 heaters of 1,500 W. Their placement should follow the layout of the tables. In stronger wind conditions or a completely open terrace, count on the upper limit or higher, while investing in wind screens may improve the situation more than an additional heater.
Do I need to address any electrical requirements for power above 3,000 W?
Yes, definitely. Heaters with
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