Fastwarm Underfloor Heating Review 2026: Products, Thermostat & Honest Verdict

At a glance

What is Fastwarm?

Fastwarm is one of the UK’s fastest-growing online underfloor heating suppliers. The company was incorporated in 2020, though the team behind it brings over two decades of experience in the underfloor heating industry. That background shows: product specs are well-chosen, technical support is knowledgeable, and the documentation is more comprehensive than you’d expect from a brand of this age.

The pitch is straightforward: quality electric and water-based UFH systems, sold online, dispatched quickly, with strong customer support baked in. The company has also begun expanding into trade, with field sales representatives now covering the UK merchant market.

Their Trustpilot rating sits at 4.9/5 from more than 2,600 verified buyers, which is about as strong as it gets in the home heating sector. It’s not marketing copy; it reflects something real about how they handle customer queries and resolve problems.

If you’re new to underfloor heating entirely, it’s worth reading our beginner’s guide to underfloor heating first, then come back when you’re ready to compare suppliers.

Fastwarm product range

Fastwarm offers three main types of underfloor heating system, putting them in the same territory as the bigger brands.

Electric heating mats

The mat systems are what most Fastwarm customers buy. You roll them out on a prepared subfloor, tile or board over the top, connect to a thermostat, and you’re done. They’re designed for bathrooms, kitchens, conservatories, and single-room retrofits.

The key spec: 2mm Teflon-coated dual-core heating cable. At 2mm, these are among the thinnest electric cables sold in the UK, which matters when you’re tiling. Every millimetre of cable height affects adhesive bed depth and potentially your finished floor level.

Wattage options: 150W/m² vs 200W/m²

Fastwarm mats come in two output ratings, and this is where a lot of buyers hesitate.

• 150W/m² is suitable for rooms where underfloor heating is the secondary heat source, supplementing radiators, or in spaces that already retain heat well (a bathroom that warms quickly, for instance).
• 200W/m² is the stronger option, recommended when UFH is the primary or sole heat source in a room, or where floors have higher thermal mass (stone tiles, thick porcelain, concrete screed).

The Fastwarm 200W electric mat kit has become one of their most searched products. If you’re doing a tiled bathroom or kitchen floor and want the heating to function as the primary warmth source rather than a luxury extra, 200W/m² is the right choice. The higher output means faster heat-up times and the ability to keep pace with heat loss on cold days.

Kits come in standard sizes from 1m² upward, and Fastwarm’s free design service will produce a layout for irregular rooms. As a rough guide, expect to budget £15–£30 per m² for the mat itself, depending on wattage and kit size.

Loose-wire electric kits

For rooms that aren’t a clean rectangle (utility rooms with island units, L-shaped bathrooms, open-plan kitchens), loose-wire systems offer flexibility that mat systems cannot match. You lay individual cable in a custom pattern, typically at 50-150mm spacing depending on output required, securing it as you go, then tile or screed over the top.

It’s more involved to install than rolling out a mat, but the result is a fully bespoke cable layout optimised for your exact space.

Water underfloor heating systems

Fastwarm also supply wet (water-based) UFH kits: manifolds, pipe, insulation boards, thermostats. These are whole-house systems connected to your boiler or heat pump, typically installed during new builds or major renovations.

Water systems are significantly more efficient to run than electric over the long term. If you’re heating more than one or two rooms, or pairing with a heat pump, wet UFH nearly always makes more financial sense. See our full guide to wet underfloor heating systems for the detail on that decision.

Fastwarm thermostat review

The thermostat is where most customer questions originate, and according to search data, it’s what the majority of people looking into Fastwarm actually want to understand. So let’s be thorough.

Standard digital thermostats

Fastwarm’s entry-level option is a straightforward programmable digital unit. You can set heating schedules, adjust floor temperature limits, and the included floor sensor probe sits in the screed or adhesive bed to prevent the floor surface from overheating. This matters particularly with expensive flooring materials: engineered wood, LVT, and certain stone finishes have manufacturer-specified maximum floor temperatures, and the sensor cuts power if that limit is reached.

Most customers find the standard thermostat perfectly adequate for a bathroom or single-room installation.

The Heatmiser range

For buyers who want a premium wired or wireless thermostat, Fastwarm stock Heatmiser controls. Heatmiser is a well-established UK thermostat manufacturer with a strong trade reputation, and their Neo range is a step up in build quality and functionality. If you’re having an electrician install the system and they prefer a brand they already know, Heatmiser is a credible choice.

The WiFi smart thermostat (Smart Life / Tuya)

For remote smartphone control, Fastwarm offer a WiFi-enabled thermostat. Unlike brands that develop proprietary apps, this thermostat runs on the Smart Life platform, which is built on Tuya’s widely-used smart home infrastructure. Smart Life is available on iOS and Android and is the same app used by hundreds of compatible smart home devices globally.

In practice, this is both a strength and a limitation. The app is mature, reliable, and familiar to anyone already in the Tuya ecosystem. On the other hand, if you were hoping for a branded Fastwarm experience with detailed energy monitoring or integration with a specific smart home platform, this is a more generic setup.

The 2.4GHz network requirement

This is the most common issue reported by Fastwarm thermostat owners, and it isn’t prominently flagged in the packaging.

The Fastwarm WiFi thermostat only connects to 2.4GHz wireless networks. It will not connect to 5GHz.

Modern routers typically broadcast both frequencies. Some use a combined ‘smart’ network that assigns devices automatically, which usually works fine. Others broadcast two separate networks (e.g. “MyHome” at 2.4GHz and “MyHome_5G” at 5GHz). If that’s your setup, connect the thermostat to the 2.4GHz version explicitly.

If you’re unsure which your router uses, check the admin panel (usually at 192.168.1.1 or via your ISP’s app) and look for band settings. Temporarily labelling your 2.4GHz network with a distinct name during setup saves a lot of frustration.

App setup: what to expect

Download Smart Life, create an account, and pair the thermostat using a QR code or manual connection process. The pairing has been streamlined in recent app versions. One consistent piece of feedback from customers: the in-app screens don’t always match the printed manual exactly. If the two diverge during setup, follow the app.

Once connected, Smart Life gives you:

• Remote temperature adjustment
• Weekly scheduling with multiple daily time periods
• Holiday mode
• Floor temperature limit setting (this is the overheating protection for your flooring — set it according to the flooring manufacturer’s guidance)

For most tile floors you can safely set the limit to 27-28°C. Engineered wood, LVT, and laminate flooring typically require a maximum of 27°C; always check your flooring manufacturer’s specification before setting this, as exceeding it can void the floor warranty.

For a broader look at smart thermostat options and how they compare, see our guide to smart thermostats for underfloor heating.

Installing Fastwarm under tiles

Tile floors are the most popular application for Fastwarm electric mats. Tiles conduct heat well, and a 200W mat under porcelain or ceramic creates a genuinely warm floor within 20-30 minutes.

Do you need backer board?

If you’re laying tiles on a timber subfloor (joists and plywood), you need a tile backer board. It creates a stable, non-flexing base for the tiles and also insulates below the heating cables so heat travels upward rather than into the floor structure.

Cement fibreboard backer (6-12mm thick) is the standard choice. Some installers prefer XPS (extruded polystyrene) insulation boards specifically rated for electric underfloor heating; these reflect heat back upward and can improve system efficiency noticeably.

On a solid concrete subfloor, backer board isn’t always necessary, but insulation below the cable is still recommended on a ground floor slab. Without it, you’re heating the concrete rather than the room above.

Step-by-step: Fastwarm mat under tiles

1. Prepare the subfloor: clean, level, and dry. Grind back any high spots.
2. On timber: fix backer boards using screws and tile adhesive, then tape the joints.
3. Dry-lay the mat to check positioning. Keep cables at least 50mm from walls and clear of permanent fixtures.
4. Mark the thermostat position and route the cable conduit down the wall.
5. Bed the mat into flexible tile adhesive. Do not cut the heating cable; you can cut the mesh between runs to navigate around obstacles.
6. Insert the floor sensor probe in a separate conduit between two cable runs, typically 300-500mm from the wall.
7. Allow adhesive to fully cure before switching on: minimum 24 hours for rapid-setting adhesive, 72 hours for standard.
8. Connect to the thermostat following the wiring diagram, or have a qualified electrician do it.

If you encounter problems after installation, our underfloor heating troubleshooting guide covers cold spots, sensor errors, and thermostat faults in detail.

Fastwarm running costs

Electric underfloor heating costs more to run than wet systems, but for individual rooms it’s the most practical option.

A rough guide for a 200W/m² Fastwarm mat in a typical bathroom:

• Floor area: 4m² (small-medium bathroom)
• Installed wattage: 800W (4m² × 200W/m²)
• Daily use: 2 hours on a schedule
• Daily energy use: 1.6 kWh
• Daily cost at 24p/kWh: approximately 38p
• Annual cost: approximately £140 at 2 hours per day (real usage will typically be lower)

Good thermostat scheduling cuts actual run time significantly. A well-insulated bathroom doesn’t need continuous heating; the thermostat cycles the mat in short bursts to maintain the set temperature.

For detailed cost modelling across different room sizes and usage patterns, use our underfloor heating cost calculator or read the full underfloor heating running costs guide.

What do customers actually say?

Fastwarm’s 4.9/5 Trustpilot score is the highest of any major UK underfloor heating supplier. With 2,600+ reviews, it’s a meaningful sample.

The consistent themes in positive reviews:

• Technical support quality: multiple reviewers specifically mention calling with installation questions and getting knowledgeable, patient responses. For a product many DIYers are tackling for the first time, this matters.
• Delivery speed: next-day dispatch is mentioned frequently, which is useful when you’ve booked a tiler and need materials to arrive on time.
• Free design service: the CAD layout drawings remove guesswork about mat sizing and cable routing.
• Product quality: very few complaints about defective cables or thermostats.

The negatives that do appear:

• WiFi thermostat setup: the 2.4GHz requirement catches people out, and the manual-vs-app inconsistency adds unnecessary friction.
• Brand recognition with trades: some customers report that their electrician or tiler hadn’t heard of Fastwarm and was initially sceptical. This isn’t a quality issue, but it’s worth knowing if you’re relying on a third party to sign off the work. Fastwarm’s move into merchant sales and trade representation should improve this over time.

Fastwarm vs the competition

Fastwarm vs ProWarm

ProWarm is the other UK brand that regularly tops DIY underfloor heating recommendations. If you are weighing up brands before fitting a system, our underfloor heating installation guide explains the practical installation stages. Both sit in the mid-price bracket, both offer electric and water systems, and both have strong Trustpilot scores (ProWarm at 4.8/5 from 1,000+ reviews).

Fastwarm’s edge: thinner cables (2mm), a marginally better Trustpilot rating, and fast delivery.

ProWarm’s edge: longer market presence and better trade recognition, which counts when an installer needs to specify a brand they’re confident recommending.

Fastwarm vs Warmup

Warmup is the premium option: higher prices, but an exceptional smart thermostat ecosystem (the 6iE is genuinely the best electric UFH thermostat on the market) and decades of brand heritage.

If smart home integration, energy monitoring, and a polished app are priorities, Warmup is probably the better choice. If you want strong value, fast delivery, and are comfortable configuring the thermostat yourself via Smart Life, Fastwarm delivers most of what you need for less money.

Our complete UK underfloor heating brands guide covers the full comparison across eight suppliers.

A note on Screwfix: Fastwarm isn’t stocked there, but if you need trade-counter collection, Screwfix carries Klima (a solid budget option), alongside Warmup and Sunstone. See our underfloor heating mats guide for a full breakdown of which brands are available where.

Pros and cons

Pros:

• 4.9/5 Trustpilot rating, the highest of any major UK UFH supplier
• 2mm cables, the thinnest available and ideal for tight tiling tolerances
• 50-year cable warranty
• Heatmiser thermostats available for trade-quality control
• Free bespoke design service with CAD drawings
• Fast UK delivery; products available from fastwarm.com, B&Q, and Amazon
• Excellent telephone technical support

Cons:

• WiFi thermostat requires 2.4GHz only, which is poorly communicated in the packaging
• Smart Life app is generic rather than purpose-built for heating
• Less trade brand recognition than Warmup or ProWarm (improving as they expand into merchants)
• Water system range is less comprehensive than specialist wet-system suppliers

Who should buy Fastwarm?

Fastwarm makes most sense for:

• Bathroom, kitchen, or utility room electric mat installations
• Online buyers who need fast delivery to fit a booked tiler’s schedule
• Competent DIYers who are comfortable calling technical support when needed
• Anyone tiling over the mat who wants the thinnest possible cable profile

It’s probably not the right call if:

• Your electrician or installer has a strong preference for a brand they already know
• You want the most sophisticated smart thermostat on the market (look at Warmup’s 6iE)
• You’re heating a whole house and need a comprehensive wet system with full trade support

Verdict

Fastwarm is a genuinely good product backed by exceptional customer satisfaction. The 4.9/5 Trustpilot rating reflects real strengths: quick delivery, helpful technical support, and reliable product quality across the range.

The 2mm cables are a tangible advantage for anyone tiling, and the 50-year warranty is hard to argue with. The WiFi thermostat works well once you navigate the 2.4GHz requirement, and knowing it runs on Smart Life sets realistic expectations about the app experience. For buyers who want a step up in controls, the Heatmiser range is a solid option.

Fastwarm is to electric underfloor heating what Wunda is to wet systems: a newer, leaner online brand that has earned its reputation through execution. Both punch above their weight. See our Wunda underfloor heating review if you’re weighing up whether to go electric or water-based.

Rating: 4.5/5 — Recommended, especially for electric mat installations under tiles.

New to underfloor heating? Start with our beginner’s guide →