First year with a PW II

First year with a PW II

I have now had a PW II for a year and on the whole it's been worthwhile.
In the UK there are no government incentives to install batteries and the PV incentives are now very small so I was interested to find out when/if it would pay for itself.

During the year before the PW was installed our PV self consumption was about 35%. Some load shifting to daylight hours was achievable (dish washer, washing machine and some car charging) but in a lot of cases it was impractical e.g. cars were only at home during the day at weekends and then they would be competing with the kids who turn up with their dirty clothes needing to be washed there and then.

In the year since the PW II install our self consumption has increased to 87%. Since in the UK there is no net metering and we do not get paid for exported power that equates to a saving of £795. At 5% apr that equates to an 9.2 year payback.

The backup gateway is not available in the UK so there are no additional benefits such as brownout cover but when it does arrive I for one will be installing it immediately as during this year we had 3 scheduled power outages and 13 unscheduled power cuts.

Despite the recent time based controls I have not been able to set the battery to charge during off-peak. Even in "cost saving" mode I assume it considers my PV system is strong enough to charge the battery the following day - which generally is the case during the summer but we'll see how it fares when the days draw in.

Reliability has been pretty awful. Early FW releases often caused the battery to sit in standby while my excess PV was just exported. Originally the Neurio sensors were WiFi connected but that proved to be unreliable so when the RS485 plugs became available they became wired connections, This improved their ability to follow generation and load changes but they still need restarting occasionally so the system is not yet at a fit and forget level.

The app has improved but still lacks the ability to drill down to the daily / half-hourly level. This is especially important as half-hour metering is starting to be offered by a number of power companies here. Although I dislike Apple, it appears that the Apple version of the app is more reliable than the Android one. I have had many times when the Apple app will connect when the Android one just throws a connection error (even though other apps on that phone connect to the internet OK).
The second feature I would like to see is guest access to the app. I would like my wife to be able to see the system status without the ability to inadvertently alter the custom settings. A Samsung TV app would be nice! (other TVs are available) or even a more comprehensive website published from the gateway.

There are loads of unquantifiable benefits. The main one being not having to be a slave to when the sun shines. If my daughter decides she "just has to" do a clothes wash at 9 p.m. I'm not going to grumble as there is usually enough reserve in the battery to cover a wash at that time. If my wife forgets to plug the car in when she returns from work, missing the off-peak window, we can still get 20 miles or so into the car in the morning from the battery.

So … Yes - it was worthwhile. I'm not sure I would recommend it to my mother as it is not yet "utility grade" reliable but it's getting there.

The proof - I have a second PW II and a UK Backup Gateway on order. I know the law of diminishing returns will apply so the savings on the second PW will be far less but it's been an interesting ride so far.

Tesla-David | July 8, 2018

@sashton, thanks for your summary. I will also keep posting about how our PW2's are working in Washington State. So far I am totally satisfied. I am not seeing any unexpected problems, and the Tesla app on our IPAD is very informative and giving us everything we need to track our performance.

dortor | July 11, 2018

thank you for your update - I'm hoping the reliability problems will get better over time.

pearnest | July 13, 2018

Have had mine for about 6 months here in Texas and have had zero issues.

Tesla-David | July 13, 2018

@pearnest, glad to hear your PW2's are doing fine after six months. I am 20 days in after our installation and am ecstatic beyond belief at how well they are performing in self-powered mode with backup set at 50 percent. We are currently exporting 63 percent of our solar back to grid after satisfying our home + EV charging requirements, and charging the two-PW2's. This is an amazing product IMHO.