My experience has been that my first gen smart meters installed by PG&E back in the mid 2000’s have pretty good time resolution, but are limited by communications speed. This model, formerly from GE, outputs new meter values every 5 sec or so, communicates with the utility far less frequently.
I have a very small percentage of estimated reads, which occurs for two reasons- 1) Power outages and 2) Utility communication issues using the utility’s limited network. My parents who live elsewhere and use a different utility but still get their data in 15 minute increments, but were seeing far more estimated reads, and another Sense user in the same city was only seeing 50 actual reads out of 768 total per day, or only 6.5% actual (link below). I believe this user was suffering from limits in the utility’s communications network.
My Green Button energy usage data from PG&E is available in 15 minute increments for all my meters (I have 5 in an apartment building). Devices like the Rainforest Automation Eagle can read meters closer to their full rate (sample every 4-5 seconds) via a Zigbee/zwave connection, then send to the cloud or a local computer. I use a few of these for the apartments. I find that they are generally pretty good though much lower resolution than Sense. They are also more painful to set up than Sense, and tougher to keep connected to both the meter and local WiFi/Ethernet. The new Sense-enabled meters get around the utility’s communications limitations by piggybacking off of the users’ internet connection.