Since I got the PowerWall installed, I've used essentially no energy from the grid; I've only sold energy to my utility. I've been dreading the time when I don't feel comfortable at night without air conditioning. Thursday night, 5/23/19, was a bit uncomfortable with a low of about 78 deg. So, I left the air conditioner on last night, 5/24/19. It wasn't a good test because the low was about 76 deg.
The result: about 7:30 am I'm producing over 1kw. The air conditioner pulls a peak of about 1300 watts but relatively briefly. Average is 300-800 watts. So, the PowerWall has hit it's minimum. That is 12%. The PW will revert to grid power at 10% in order to leave a little energy for a real power failure. So, a near thing. Especially for a not very demanding night.
It is silly for me to worry about pulling a little grid energy. My cost would be around $.10 per kwh used. For an hour or two in the early morning hours, that cost would likely be $.05 to $.15. Insuring remaining off the grid would require a second PW battery. Cost, around $8k.
I can continue to make the claim of having used no grid energy since the PowerWall install. Let me look that date up.....1/26/19.
https://wmckemie.blogspot.com/2019/01/powerwall-install.html
Four months tomorrow! I may continue to forgo night time air conditioning for a while. Though I'm sure now that a hot night will exhaust the PW battery.
I finish writing this about 7:50 and the PW is charging at a few hundred watts whenever the air conditioner is cycled off. Charge level remains at 12%. This is a cloudy morning, so far. 12 hour overnight air conditioner consumption was 3.91kwh. The first hour consumed .62kwh due to the warmer conditions.
Sunday, 5/26/19
It looks like we are in for a string of mid 70s nights so I have suspended overnight air conditioning experiments.
Sunday, 6/9/19
I just went through the first night with air conditioning running all night. My minimum charge level was about 13%. I'll probably start running the air conditioner around the clock.
Saturday, 6/22/19
I've been through several nights running the air conditioner. I've come close to hitting the reserve threshold of 3%; the lowest has been 6%, I believe. Once the threshold is hit, grid power is used. So, I have so far avoided using grid power even using overnight air conditioning.
I decided to buy a 6k btu window unit for the bedroom so I could avoid running the big unit overnight. Last night was the first using only the small new unit. The PW got down to 30% just before morning production began. So, a success! This gives me confidence that I can sleep comfortably during a long term grid down situation. A major step!
We are using the thermal mass of tons of concrete to capture the mid-70s night temperature. No air conditioner use yet. It does take a bit of effort to open and close all the windows, though.
ReplyDeleteI consider myself too old to build a new house. As it turns out, I am NOT too old to add more PV. Or more PW.
ReplyDeleteThough I DO admire your house!