ZBB
Emperor
Another Houston-area person here... Our system is 16.3kW (48 350W panels) with 4 Powerwalls (so very similar to @bob_p )... Our install was in late June, and we're still waiting for PTO from CenterPoint (its at the CenterPoint inspection stage, so hopefully soon...). But we've been disconnecting from the grid most nearly every day (all except a couple very rainy days and while we were on vacation in July).
While we were waiting for install, I did a bunch of modeling using the Smart Meter Texas data (although we had less than a year of data so had to estimate a few months -- new construction house that we moved into in July 2020). @bob_p was also kind enough to respond to a few questions I had on plans -- and after reading his posts and doing analysis, we decided to select a free nights plan instead of a NEM plan. We selected a different plan that has the free night period from 8pm to 6am -- but it modeled better with our usage pattern than a free night plan that had 9pm to 9am from a different provider.
In our case, we expect the solar to generate ~82% of our estimated annual usage (again, we didn't have a full year of data, but we did have Aug-May data). Looking back, the estimate I did for June/July was slightly high -- but close enough. Our prior contract expired in mid Jun -- and we went ahead and moved to a free nights plan about a week before the install. We also had an issue with one of the inverters, which Tesla replaced in late July.
What we are seeing so far matches the modeling we did. We expect to only pay the minimum grid connect charge (currently $4.39 with CenterPoint) each month, with the only on-peak charges happening if there is a Storm Watch event that needs to charge the PowerWalls during the peak period (which would cost ~$8 for a ~80% charge). I've already enabled the Cost Savings mode and put in the on-peak/off-peak times into the Tesla app, and the Gateway has not been pulling from the grid during peak periods with the backup reserve set to 25%. If this holds, I would expect our annual grid bills to be ~$75 annually (which assumes a little on-peak grid draw, but most of the bill is the minimum charge).
I also did another a comparison with one of the NEM plans a week or so ago (Tesla was asking if we were going to use their co-branded MP2 NEM plan or not). Since our system is expected to generate ~82% of our usage, we would expect to pull around 4,000 kWh from the grid per year. The NEM plans I reviewed for Texas do not have TOU rates, and some of the EFL info ("Electricity Facts Label" -- what the regulator requires each power provider to publish so consumers can better compare rate plans) was very hard to decipher (the MP2 plan for example may not even comply with the law -- it did not specify how to calculate a bill or show anything other than the average rate)... Some of the NEM plans purchase back at the combined generation + delivery charge, while others only cover the generation charge. Most of them also cap the generation credit at your total usage on a monthly basis (so you would never be in a net credit scenario). So you really will need to do your homework on comparing these plans. But assuming you pick one that buys and sells at the combined rate, it still means we would have a net draw. These plans are currently around $0.11-0.12 per kWh and most have a monthly fixed fee around $10 which means that purchasing 4,000 kWh annually would result in annual charges of around $600. That's "only" $50 per month, but that's still nearly 10x what we expect our bill to be using the free nights plan.
I fully expect these free nights plans to eventually not allow solar customers, but for now we have one. Contract runs to June 15 next year...
One other note -- the power providers change pricing all the time. The pricing we have on our plan was locked in June for 12 months. But looking up the plan we are on now, the on-peak price is about 10 cents higher (ours has a combined rate just under 19 cents/kWh, and its now 28 point something... I've heard that the best times to price plans in TX are in the fall/spring shoulder periods -- so if you have flexibility on when you start a plan, that may be a good idea...
While we were waiting for install, I did a bunch of modeling using the Smart Meter Texas data (although we had less than a year of data so had to estimate a few months -- new construction house that we moved into in July 2020). @bob_p was also kind enough to respond to a few questions I had on plans -- and after reading his posts and doing analysis, we decided to select a free nights plan instead of a NEM plan. We selected a different plan that has the free night period from 8pm to 6am -- but it modeled better with our usage pattern than a free night plan that had 9pm to 9am from a different provider.
In our case, we expect the solar to generate ~82% of our estimated annual usage (again, we didn't have a full year of data, but we did have Aug-May data). Looking back, the estimate I did for June/July was slightly high -- but close enough. Our prior contract expired in mid Jun -- and we went ahead and moved to a free nights plan about a week before the install. We also had an issue with one of the inverters, which Tesla replaced in late July.
What we are seeing so far matches the modeling we did. We expect to only pay the minimum grid connect charge (currently $4.39 with CenterPoint) each month, with the only on-peak charges happening if there is a Storm Watch event that needs to charge the PowerWalls during the peak period (which would cost ~$8 for a ~80% charge). I've already enabled the Cost Savings mode and put in the on-peak/off-peak times into the Tesla app, and the Gateway has not been pulling from the grid during peak periods with the backup reserve set to 25%. If this holds, I would expect our annual grid bills to be ~$75 annually (which assumes a little on-peak grid draw, but most of the bill is the minimum charge).
I also did another a comparison with one of the NEM plans a week or so ago (Tesla was asking if we were going to use their co-branded MP2 NEM plan or not). Since our system is expected to generate ~82% of our usage, we would expect to pull around 4,000 kWh from the grid per year. The NEM plans I reviewed for Texas do not have TOU rates, and some of the EFL info ("Electricity Facts Label" -- what the regulator requires each power provider to publish so consumers can better compare rate plans) was very hard to decipher (the MP2 plan for example may not even comply with the law -- it did not specify how to calculate a bill or show anything other than the average rate)... Some of the NEM plans purchase back at the combined generation + delivery charge, while others only cover the generation charge. Most of them also cap the generation credit at your total usage on a monthly basis (so you would never be in a net credit scenario). So you really will need to do your homework on comparing these plans. But assuming you pick one that buys and sells at the combined rate, it still means we would have a net draw. These plans are currently around $0.11-0.12 per kWh and most have a monthly fixed fee around $10 which means that purchasing 4,000 kWh annually would result in annual charges of around $600. That's "only" $50 per month, but that's still nearly 10x what we expect our bill to be using the free nights plan.
I fully expect these free nights plans to eventually not allow solar customers, but for now we have one. Contract runs to June 15 next year...
One other note -- the power providers change pricing all the time. The pricing we have on our plan was locked in June for 12 months. But looking up the plan we are on now, the on-peak price is about 10 cents higher (ours has a combined rate just under 19 cents/kWh, and its now 28 point something... I've heard that the best times to price plans in TX are in the fall/spring shoulder periods -- so if you have flexibility on when you start a plan, that may be a good idea...
