Altimeter Watch Accuracy

So I finally entered the world of altimeter watches. I got a COROS Vertix. It uses a barometer for the altitude.
Hey have noticed discrepancies in the same area over time. For example, my house is at 840 feet. If I set it, going to work and back over a few days, it will change as much as several hundred feet. Is this expected or are there more accurate options?

Altitude uses a barometer, which just reads air pressure. The altitude will appear to change over time as air pressure changes with weather systems. An apparent increase in altitude while actually at a fixed known altitude indicates a decrease in pressure. This typically means poor weather and can be used as a field forecasting tool. If the watch has a direct barometer reading you can also check that to be sure.

Unlike a GPS device that gives altitiude info based on satellite readings, a watch calculates altitude using barometric pressure.

As weather conditions change, so will your altitude reading change.

From my Suunto watch manual: “Since the altitude is shown based on the atmospheric pressure reading it will be effected by pressure changes”.

At best,  my watch readings are usually just “close” to actual real “map data”

Watches with GPS functionality are a more accurate option.

Calibrate, calibrate, calibrate.

As these usually use barometric pressure to calculate altitude, you will have to calibrate them at least once a day, sometimes even more. When you're on a trek/hike/climb and you're at a known height, check your altimeter and recalibrate. I usually do this when arriving at a refuge, or when you're on a fixed point on the map, such as a summit or shoulder.

Alternatively, some watches allow for altibaro or GPS combination, such as my Suunto Ambit 3 Peak. But this will generally be a huge drain on your battery so I usually don't run this. 

Shelton Hatfield wrote: Watches with GPS functionality are a more accurate option.

It depends.

GPS elevations are unbiased but noisy. If you stand still for a few minutes and monitor your GPS elevation it'll often bounce up and down. With a good view of the sky the error is usually within 50' or so. But in steep terrain it can be much worse. If you're halfway up a big cliff you may not be able to get any GPS reading at all.

Barometric elevations, on the other hand, are precise but biased. If you're standing still they won't bounce around like GPS elevations, but they tend to drift out of calibration as you gain or lose altitude. Even if it's calibrated when you start, if you climb up several thousand feet a barometric altimeter can easily be off by a couple of hundred feet by the time you get to the top.

Victor is correct in what he says. I ignore my altimeter until I'm starting the trek on foot and can set the reading to the known altitude. Anytime you get to where you know what the true altitude is you should check your watch and match it.