Efficiency or performance - what's the difference?

I was in the shop yesterday going through my spiel with a visitor and the efficiency question popped up as it always does. "Is this one efficient?". This question gets asked almost every time and I listened to myself answering this very important question.

My answer goes something like this: "Are we talking about efficiency, or performance? People think efficiency means its going to give a lot of heat. Well it doesn't. It actually means whether it will require a lot of energy to reach a temperature, blah blah blah....."

I thought to myself, shut up. People ask if a radiator is efficient meaning does it give a lot of heat, irrespective of what the actual dictionary definition means.  Remember literally? The dictionary definition actually says it also means figuratively. The reason being, its now used that way.

So, I need to reformulate how I answer this question, but in order to do so, I'll explain how this all works.

Efficiency literally means efficient. Something is efficient when it takes little energy to operate. A low powered car, say 1 litre is going to work using less fuel, but it isn't going to have huge horsepower.

Then we have the comparison of performance. A high performance car is going to have high horsepower, torque, top speed, etc. At the expense of all this power, its going to require more fuel.

Which radiators are efficiency and which are performance and why?

Aluminium are almost without exception high efficiency because they ordinarily have a core in the centre of a section or profile. This holds a small amount of water. The section is then joined together and air channels are created. This helps to create a chimney effect where the cool air is heated by the core and warm air convects from the top. This is a highly efficient method of utilising heated water to provide heat.

Column radiators, cast iron radiators and steel tube on tube radiators rely on a volume of water inside the tubes or sections which heat the surface of the radiator. This is where the name radiator comes from. Radiant heat. This is less efficient as it requires more water reaching the surface and emitting from the surface.

Interestingly, at my first job in radiators with Thermal Radiators Ltd, they made low surface temperature radiators consisting of two parts. The case (which was actually used to convect heat with grilles at the top) and the emitter, which was a tube on tube radiator inside the case. Essentially, they utilised both methods. Great radiators, sadly they got too expensive being UK made and with the factory being Nevil Shute's old aircraft hangar, it was made of asbestos and had to be pulled down in the early 2000s. Any Portsmouth locals will be interested to know this is now the site of Hampshire Constabulary's head office on Airport Service Road. I digress....

There is another form of radiant / convector radiator. Its called a pressed steel panel radiator, or bog standard radiator. They are very efficient and offer high output. Chances are, you're tearing some of those out to replace with pretty radiators. We only really do pretty radiators. We can get panel rads, but that's not what you're here for and you can get these easily elsewhere for next to nothing. If you are looking for panel rads, you're more than welcome to keep reading this invaluable trove of useful information, but when you're done, have a look at Screwfix, or better still let your plumber get them.

Back to answering the question. This all sounds simple enough, but I need to explain this without sounding like I'm correcting. Really, I need to turn the question around.

Say if they're looking at a radiant radiator.

Q: "Is this one efficient?".
A: "It'll give you a lot of heat, but it'll take more water to do so" Sounds a bit negative.

A: "Yes, it puts out lots of heat because it has a lot of surface area. Are you looking to improve running costs or to be really warm? These are great for maximum output. If you're looking a low water content, then aluminium may be a solution for you." Sounds more positive / less schoolmarm like.

OK. Done.

Full disclosure. I have steel column radiator in every room in our house, except for the kid's room which has a vertical tube on tube radiator in bright red. I don't pay the gas bill, but my lovely wife Elisa never seems to moan about it, so I'd suggest we're not looking at horrendous amounts. Efficiency usually comes into play when we start looking at renewable energy such as solar or heat pumps. These systems can run at far lower temperatures where aluminium are clearly the preferred option.

Another blog post done. Good to flesh this one out and hopefully useful to someone. Especially those who come and visit and now won't get a lecture.