An added benefit to distillation, is that you don’t have to worry about NSF or other certification like you do with water filters. This is because distillation is a simple process were water is boiled and then condensed and collected into a separate container.
One distiller may be more efficient than another, it may work faster, or be more convenient to use, but the end result is the same – distilled water. One distiller will not create more pure distilled water than another.
One thing you should check however, is that the water does not come into contact with any plastic (or other chemical leaching materials) after it has evaporated. From what I have seen, even the cheapest Chinese water distillers have stainless steel boiling chambers, stainless steel condensing coils, and stainless steel outlets for the condensed water.
The cheapest countertop models come with a plastic collection jug however, which tend to be made of some very nasty plastic that makes the water wreak of chemicals. I advise you throw that one out and replace it with a glass one, or buy a distiller that comes with a glass collection jug.
Countertop Water Distillers
I personally have one of these.
Countertop distillers consist of a stainless steel boiling chamber at the bottom, a stainless steel coil-based fan assisted cooling system at the top, and a separate collection jug.
These produce 1 gallon of water in about 5.5 hours, though you can get that gallon a lot faster if you use warm water to start with. I don't advise you start with very hot or boiling water however, because this will increase the amount of VOC's that end up in your purified water (more on VOC's below).
They usually also come with a post-distillation carbon filter, which removes any remaining volatile organic compounds (VOC's). VOC's are contaminants with a low boiling point that evaporate with the water and hence are not removed by distillation. Common VOC's found in tap water include trihalomethanes (a disinfection byproduct), perchloroethylene (a byproduct of solvents), and methyl tert-butyl ether (a fuel additive).
To use this style of distiller, all you do is fill the water chamber with tap water, put the cooling unit over it, position the collection jar, and turn the unit on. Then the fan will come on, and if you used cold water, pure and natural distilled water will start to collect into the collection jar in about 30 minutes. Once the water is all used up, the unit will shut down by itself.
This is one of the smaller distillers out there, and is ideal for single users, couples, and small families.
Important tip: if you purchase one of these, please also get yourself one of these timer plugs. Without a timer plug, the machine turns off once all of the water has evaporated. This leaves a disgusting burnt sludge behind, due to super concentrated and burnt limescale. It's hard to get rid of, and some of the burnt smoke taints and adds a slight smell to the purified water. With a timer plug, you can ensure the machine turns off when there's still around a centimeter height's worth of water left inside. This also helps to extend the life of the machine. There are some complaints on line that these machines don't last longer than 6 months. However, by using a timer plug, mine lasted for 4 to 5 years of almost daily use, and that was by far the cheapest Chinese models I could get my hands on on eBay.
Here are my recommendations on specific units:
H20 Labs
My #1 go-to countertop model is the one by H2O Labs. Their product is made in Taiwan, but the company is based in the U.S. They do quality checks to ensure their product is safe and of a high standard.
I like that they make assurances that the purified water does not come into contact with any plastic – not in the boiling chamber, in the condensing coils, or in the outlet nozzle. It also comes with a glass collection jug.
I also like that you can buy spare parts on their website should something go wrong (as opposed to having to purchase an entire new unit like you do with the cheaper Chinese models).
They've also got one of the best reviews on Amazon, at 4.7 stars, vs. the 4.2 to 4.4 stars of most other models.
You can get the H2O Labs countertop water distiller here.
Megahome
The Megahome countertop distiller looks exactly the same as the H2O Labs one. I'm pretty sure both companies are selling the exact same countertop distiller.
Megahome also provides assurances that the water never comes into contact with plastic during the distillation process.
Their unit also has a 4.7 star rating on Amazon, comes with a glass collection jug
The Megahome website in the U.S. isn't very helpful, but the U.K. website is full of helpful information, a long list of different products, and separate section for ordering spare parts. Their U.K. branch also offers a 2-year guarantee, while the same unit in the U.S. has a 1 year guarantee. H2O labs also has a 1 year guarantee. If you're based in the U.K., you'd likely be better off with the Megahome unit.
You can get the Megahome water distiller here.