Any recommendations on brands? We are looking to heat 300-400sf

Hello Plumberry and Salmon Slayer,
Any electric radiant heating systems performance will depend on the conditions of it's installation, with one of the most dramatic differences being between systems installed over wooden subfloor and those installed over slab-on-grade. A system installed over a concrete slab may take 6 or more hours to heat up, as the concrete acts as a heat sink and draws most of the initial heat down instead of letting it rise. But once the slab is heated, it holds onto that heat and radiates it back into the room for a long long while. Including a layer of 6mm acoustic cork under the heating system will reduce that heating draw significantly. Systems installed over wood subfloors will respond much faster (45 minutes with most manufacturers), and will cool quickly also unless the floor is well insulated (not common). Electric radiant heatings systems should never be relied upon as a primary heating source for your rooms.
There are quite a few manufacturers of electric radiant heating systems, and each tries to balance cost against performance by reducing the space between heating elements, adjusting the gauge of the heating elements or by some variation of a matting system. Once the systems are installed and have achieved the desired operating temperature, they are pretty much all the same. A system left on from October through April can use heating elements spaced wader apart (and be less costly for materials) and still maintain a comfortable floor for about the same monthly cost. But a system that is programmed to be warm for a morning shower and a few hours in the evening only should have closer heating elements to speed up the heating process. Whatever your choice of manufacturer, a programmable thermostat is going to make your system more efficient.
Electric radiant heating systems should NEVER be installed under cabinets or other enclosed spaces. But most manufacturers will allow their systems to be installed in shower pans or on shower seats without much hesitation. Whatever your plan, you should always seek out the manufacturer's endorsement of your usage.
Brands I've used, and will continue to install are:
Laticrete Floorheat
Watts Suntouch
Nuheat
I prefer to avoid using loose cable systems. I see no advantage for my own clients from these systems, when the additional labor costs of installing a loose cable system and installing tile over it are added to the otherwise cheap raw materials.
Hope that helped?
Shaughnn

Shaughnn covered everything. Agree with shaughnn. In each sentence, one could add a detail or a "but not if"; this does not change the overall thrust of what he wrote. If I had to work for Shaughnn, or if had to hire him I know I could talk and communicate about everything necessary.

The majority of people experienced with heating cables would not think of mentioning the difference between an installation on a concrete slab or on a wood structure. Go figure. It makes a huge difference, and they don't mention it.

Operating costs depend on Watts. More wattage, more heat, more power, more consumption, more cost, they are all the same things (wattage = heat = power = consumption = cost) as long as the building's insulation is effective.

If you heat a slab that you own both sides of, and that you live both sides of, you get all the heat energy back as it acts as a radiator on both sides. If you heat a slab on grade, in a damp basement, you are heating Mother Earth and using (cold) ground water as the conductor (heat conductor) to accelerate the heat transfer into the Earth. Not as good. This is where a thermal break is a good thing. If you heat a slab on grade, and you think it's dry and won't conduct as much into the Earth as a damper comparative slab, you are right but you will still spend a lot to heat the slab, and most of the heat you are paying to produce will go into the ground. "Most" is how much? Since it's a sink, in thermal conductivity terms, it's way way more than half.

As shaughnn wrote, a question about brands will never get any specific answer, as a heating coil is a heating coil, as dumb and simple as a toaster. They are all the same as far as heating goes. In a toaster, the heating coil is "a heating coil" and nobody asks if one or another is better or the best, in a toaster. Same thing with a heating cable in a floor heating system. "It's a toaster" is a common phrase in certain engineering circles, meaning if you're consuming power, you are generating heat. It also means that's the end of that analysis, move on to the next subject, there is nothing more to ask about here. Power = heat.

Yes one can put heating coils under tubs / showers, near toilets too, and a little bit into cabinet space (but this is best when you know how to plan for heat transfer and air movement, and not advisable to the average bear, or else you get a very warm box that thwarts your goals because you have to reduce heat to compensate for the box heat, or you have to leave the cabinet door ajar, or drill holes somewhere, or...)

Mats yes. Loose cables can be pulled off a mat if needed. Buying a long loose cable is just a few extra days work, nothing serious if you have all the time in the world and nothing else to do.

To find out if he / she got it right, the average person reading about heat cables needs to post about "watts per square foot" they might want to have, and tons of information about their slab or subfloor, and the cork or other insulator or membrane as a heat break between the cables and the slab or subfloor, or about the insulation under the subfloor or about their building envelope. Although it IS possible to use electric cable radiant heatings systems as a primary heating source for a room, the average homeowner should not try to achieve this after a bit of internet reading. There are so many reasons why you may be less than satisfied that it's best not to get your hopes up.

plumberry asked for confirmation that electric is the way to go. I guess this means "electric and not a hydronic loop" but this was not specified. Since we received no information from plumberry about anything, the answer is NO, not yet, not enough is known about plumberry's situation. But it is true that electric is a great way to warm one room.

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Here is a link that might be useful: A thread that shows all the problems and ends in a Thank_You

You have been incredibly helpful. Thank you so much! Shaughnn, if you were installing a system in your house, which mfr would you pick?

There is one apples-to-apples comparison you can make when comparing one mat to another: its output in terms of BTU/h/sqft.

The higher the number, the faster the response time and the better the system will be able to heat your floor and possibly even take the chill out of the room.

Products offered today can vary from roughly 12 to over 40 BTU/h/sqft, so compare the specs when you shop. Most of the main manufacturers are up in the 12 watt/sqft (roughly 40BTU/h/sqft) range, which is the maximum allowed for an above-floor mat system. Cables can go about 25% higher. Underfloor systems are restricted to a lower value.

While most manufacturers don't rate their products as a primary heating system, and while most AHJs restrict systems like these resistance heating mats as being used as primary heating system in residential construction, you can sort of ballpark a mats capability by using 30BTU/h/sqft as a generic baseline number for average residential construction. Well below that number and it's sort of a cute boutique heating element. Approaching that number it'll warm your tile nicely. If it can output higher than that, you can have toasty floors and perhaps even a toasty room.

If a mat is rated in watts/sqft, multiply watts/sqft by 3.4 to get BTU/h/sqft. A mat rated at 10 watts/sqft would equate to 10 x 3.4 = 34BTU/h/sqft.

Radiantly, Mongo

Remember that these electric systems are floor heating systems, NOT room heating systems! YOu will still need to consider the room's HVAC needs as these will only make the floor warm, and not heat the room. If you are looking for a system to heat the entire room, then you are looking for a hydronic system coupled with a boiler and PEX piping.

Hello again, Plumberry,
Were I installing a system in my own home, I'd probably consider the Suntouch system first, but not exclusively. I've found that it's probably the best *value*, with good response time and a good price. It's designed to perform at 12 watts per square foot, so that puts us in the 40BTU/ft2 range.
Shaughnn

Appreciate the information! I will start with baselining suntouch

We've put Warming Systems cable (not mat) into several rooms in our house. Doesn't take too long to install (last project took 6 hours/2 people for 400 square feet). It goes from bone-cold "off" to "feeling warm" within 15 minutes or so.

Specs say 12 watts/sq ft, or 40 BTU/h/sqft.