Any electric tankless is going to be high efficiency, but are you sure that thing is even LEGAL to install in Canada (there are no CSA or UL ratings indicated, though they do cite some European Norm standards- not sure if they're the relevant ones, or what certifications are required in your area). Or is this being installed in Thailand, not Ontario Canada?
Do you have 150A of 240VAC to spare?
At Ontario's wintertime incoming water temps I'd be loathe to use any electric tankless, at any price point, except possibly as finish-heat/backup to a solar hot water system or something, and even then...
At Thailand's incoming water temps it's probably just fine, provided you won't melt the power lines or transformer when it's pulling full power. You really DO need to be sure the service to the house can handle the current before installing it, or you'll either be blowing breakers/fuses constantly, or damaging the power lines. At full bore it's pulling 36,000 watts, which is a lot of power. more than 10x the instantaneous power draw of the Stiebel PSH 100.
A hundred liters is not a lot of hot water, but it's plenty for one person to take a shower, and at 3000W the recovery time on the PSH 100 won't be forever.