That’s what I started out as. My 1973 masters thesis was on a specialized (inexpensive, industrially threatening) form of seawater desalination that could turn ocean bordered deserts green. Too bad a key component was labelled unsafe for humans for political reasons. Today, the technology hasn’t advanced much. True, we have micro-processors to control things and better high pressure pumps, but if watermakers were on the computer learning curve, we would all pick one up on the way home from work.
They aren’t, so I have thought a lot about whether we can justify the expense and whether we want to take on another thing to maintain. And as is my wont, I did my thinking with calculator/spreadsheet in hand.
I can’t make buying a watermaker make sense.
If we planned to circumnavigate; if we planned to really hang out in rain impoverished places weeks from anywhere else; if we didn’t have 165 gallons of tankage maybe I could. But I can’t.
We can make 165 gallons last a month. But we like our comforts, so let’s call it two weeks. If we pull into an average marina in the US every two weeks for a one night re-provisioning stop, we would allocate 6.5% of that ~$90 cost to a water fill up. Domestic water on the Chesapeake costs about $3.50 per 1000 gallons. So let’s give the marina a 10x markup to $35 per 1000 gallons or 3.5 cents per gallon or, for our tankage, $5.78 call it $6.00 for water every two weeks.[Keeping in mind this is a pseudo cost buried in the marina overhead. We are going to pay $90 for that night whether we bunker water or not.]
In the Bahamas or further south and east, on that same two-week cycle, in a bad year, we would expect to pay as much as $0.50 per gallon for water, or $82.50 to fill up the tanks in paradise.
For a year this would put us between $540 (as far as the Bahamas) and $920 (down to Grenada) for water. That’s an average of $730/year.
The watermaker we liked best was $4635 discounted. Its power appetite could be serviced by the solar panels. In clean water it would only have to be operated 1.9 hours daily over two weeks to keep up with nominal consumption. [I say nominal because everyone we have talked to with a watermaker has watched their consumption go up as a result of having a source of supply.]
It requires about $150 in supplies a year (that buying water doesn’t). So our net effective cost of water per year becomes $580. This divided into the price of the watermaker tells me it would take eight years to break even.
If we were to be cruising for eight years, I think we could safely assume the equipment would have no residual value. I think we can also safely assume we would have spent considerable hours devoting angst and attention to a complex piece of high pressure plumbing likely to become troublesome just when needed.
Frankly, we can use the storage space and be happier. Also, the whole shebang weighs in at about the same as 9 gallons of fresh water — 4.5 days for us to find a source of supply…