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Nest and Solar Logger Update

Nest and Solar Logger Update

It has now been a week since we installed the Nest 3rd Gen Learning Thermostat and we have been able to try the auto learning and heating / hot water schedules the thermostat offers.

First impressions of the thermostat overall had been positive with a simple and easy to use interface on the thermostat and iPad apps.

The central heating side of the apps and web interface seem to be very well thought out and simple to use but the hot water control seems to have been added as an afterthought and needs work to make it as user friendly as the central heating side.

The online reporting for the central heating run times are basic but give just about enough information but there isn’t any way to get an overall run time for the hot water apart from manually adding up the time on the hot water schedule but this doesn’t account for any hot water boost times which have been added/set during the week and so it isn’t possible to get an accurate total each day.

Nest SavingsWe had wrongly assumed that the Nest system kept the data logs and they would be accessible to the user after reading the following on the marketing page for the thermostat:

“See how much you saved.
Nest shows you how much energy you use every day in Energy History and every month in your Home Report. So you can see when you use more energy, like on weekends or Monday nights, and how to use less.”

After purchasing the thermostat and setting up the online account we found that only the last ten days of data are available making the history useless for longer term monitoring. With our solar PV and Hot Water logger we have historic data going back for three years and we hoped to be able to do the same with the Nest data so we could compare annual data for increases or decreases in gas and electric consumption.

Latest saved data Last Hour Day Report

Nest API Restrictions

When we completed the installation of the Nest Thermostat I signed up for the API hoping to be able to use this to access the current and saved 10 days of history from the Nest thermostat and be able to save this with our other data to use on our home reporting website (

The Nest API has a long Terms of Service and has prohibitions against being able to use the API to save your data from your own Nest Thermostat.

“you will not use the Nest API and other Nest Developer Materials to:
Collect, aggregate, re-syndicate, retain, log or store Customer Data (as defined below) received via the Nest API beyond 10 trailing days from the date when the data is received.
Create a Client that performs demand response or other energy management programs such as those offered by electric, gas, water or similar companies or energy markets.”

As making an automated online service to collate our thermostat usage data would go against the terms of use and would risk Nest closing our account which would then result in our Nest Thermostat being useless as it won’t work without an active Nest account we had to scrap our plans to automatically store the data and so we made our home reporting site so we can manually add the day’s usage via a admin page. As this has not direct connection to the thermostat (apart from looking at the data on the screen and typing it into a database) it won’t be against their terms of use!


Week Report Gas and Electric Meter Readings Nest day overview

We had also hoped to be able to use the API to schedule the hot water times so the hot water heating would go on later if the solar thermal had already raised the hot water tanks temperature but this would also be against the terms of use as it would be creating a “Client that performs demand response or other energy management programs

Overall I wish that we had done a lot more research into the restrictions of using the Nest system before ordering it and in hindsight we may have been better off making our own heating and hot water control system.

If the Nest Thermostat had a separate hot water thermometer it would have been simple for them to add this delayed start into the hot water heating within the Nest environment and after looking at the support forums it seems that this is a fairly popular feature request.

Nest Overview Nest Central Heating Schedule Nest Central Heating History

Solar Home Reporting Website Upgrade

We have now had two full weeks of data being saved from our off grid 12 volt system, home temperature and solar thermal logger and we also had over 3 years of data from the previous data logger in a Microsoft SQL Server database for our reporting website at

As the new solar logger doesn’t have the mains energy monitoring which will be added by a separate module as soon as the PCBs arrive, we rewrote the data logger website to work with the new data and also created an archive of the past three years’ data which was over 1.6 million records.

I wrote a script to create a more contact dataset of the archive data which saved a maximum and average value for every hour of each day and this was saved into a new archive database table which reduced the records down to around 28,000 records. The previous 1.6 million records were then deleted and the new archive section was added to the website to view the archived data.

I have added a new folder into our Raspberry Pi Solar Logger V2 repo on Github with the reporting website files and also a .sql database table creation script which you can download from the following link: