We will see how long this gets. From these boards and my own experience through somewhere in permitting on Los Angeles:
1. What is your usage? Its easy enough to get a year's worth of bills together if you have them. You will need to convert dollars into Kilowatt hours (Kwh) used. A couple of things right off the bat. First, there is every possibility that you will need to know not only your total Kwh used, but when (as in time of day) you use. This impacts cost generally (see Net Metering, below) and Powerwall use specifically. Second, don't forget to increase estimated usage for an EV. Let's say your house uses 35kwh in a day. The Tesla Model 3 battery is 75 Kwh. Often, even if you already have an EV incentives have masked how many extra Kwh you use.
2. Do you want to cover all of that usage? Note that photovoltaic (PV) systems are rated in Kwh, but that number has to be converted. For example, my neighbor's "7.2 Kwh" system is producing an average of 40 kwh per day on sunny days. Also, the "7.2" Kwh is aspirational - a system virtually never reaches its maximum rating in any given hour. Both Tesla and a site named PVWatts will estimate yearly usage, however .......
3. What can your roof hold? Everyone's roof is different, and two identical systems will produce significantly different results in different locations and different orientations. I have a relatively flat roof, but you can see other layouts on these boards where the system is divided between several sections of roof, facing different directions. Any annoying factor at this point is some utilities actually limit the size of a system they will approve.
4. Do you want battery back up? If you are in a fire or storm zone, Powerwalls can run your house in an outage. If you are in a place where you normally don't lose power much, Powerwalls are more like a combination of insurance policy/green upgrade. Because powerwalls can charge when the sun is out and your usage is low, and then be discharged at night, they allow for some savings because many utilities charge a premium per Kwh in the evening, so Powerwalls can save money but typically not as much as they cost.
5. If you want battery back up, learn about sizing the powerwalls to the overall system. You want about one Powerwall per every 5kh of expected solar production, because that is what Powerwalls can accept. Allowing for the fact that there is loss. In my case I expect three powerwalls (15kwh max) to be well matched to a Tesla 16.32Kwh system.
6. So, far, so reasonably complicated. Next, it starts to get a bit ugly. If you want Powerwalls, how much of your house to you want them to back up? This requires acquiring a rudimentary knowledge of electronics. One super basic way of starting this is to realize each powerwall can put out about 30 amps. Amps are useful because many of us understand our breaker switches. However, it is also immediately apparent that 30 amps is nowhere near enough to run an entire house with any significant electrical appliance. The accepted rule is that three or more Powerwalls truly can power an entire house. Two powerwalls could be close. The reason this is critical is that there is significant electrical engineering involved in separating the "backed up loads" from the "non-backed up loads" in a partial home back up.
7. Next, there is no way of avoiding the math. Figure out the cost of your bill, then applicable rebates, including ones for powerwalls. Its pretty likely you will be saving money regardless, but because you can pay with cash or finance, there is some relatively complex math to do to understand what you are buying.
8. By this point you would have a good idea of what you are actually going to buy for the money. Comparing Tesla to other companies for equivalent systems is next up. Tesla compares well on price, but many say that Tesla is poor on customer service.
9. Get ready for the process. Because solar and battery systems require permits from a utility, and approval of plans, they take time. During that time, if you go with Tesla (or even if you don't) there is a lot of waiting around. Plus, you need to decide where to locate stuff (panels, conduit, powerwalls, extra breakers, etc). Location by itself is a significant design decision. Tesla generates a layout of the panels very quickly. Final approval of plans takes longer.
1. What is your usage? Its easy enough to get a year's worth of bills together if you have them. You will need to convert dollars into Kilowatt hours (Kwh) used. A couple of things right off the bat. First, there is every possibility that you will need to know not only your total Kwh used, but when (as in time of day) you use. This impacts cost generally (see Net Metering, below) and Powerwall use specifically. Second, don't forget to increase estimated usage for an EV. Let's say your house uses 35kwh in a day. The Tesla Model 3 battery is 75 Kwh. Often, even if you already have an EV incentives have masked how many extra Kwh you use.
2. Do you want to cover all of that usage? Note that photovoltaic (PV) systems are rated in Kwh, but that number has to be converted. For example, my neighbor's "7.2 Kwh" system is producing an average of 40 kwh per day on sunny days. Also, the "7.2" Kwh is aspirational - a system virtually never reaches its maximum rating in any given hour. Both Tesla and a site named PVWatts will estimate yearly usage, however .......
3. What can your roof hold? Everyone's roof is different, and two identical systems will produce significantly different results in different locations and different orientations. I have a relatively flat roof, but you can see other layouts on these boards where the system is divided between several sections of roof, facing different directions. Any annoying factor at this point is some utilities actually limit the size of a system they will approve.
4. Do you want battery back up? If you are in a fire or storm zone, Powerwalls can run your house in an outage. If you are in a place where you normally don't lose power much, Powerwalls are more like a combination of insurance policy/green upgrade. Because powerwalls can charge when the sun is out and your usage is low, and then be discharged at night, they allow for some savings because many utilities charge a premium per Kwh in the evening, so Powerwalls can save money but typically not as much as they cost.
5. If you want battery back up, learn about sizing the powerwalls to the overall system. You want about one Powerwall per every 5kh of expected solar production, because that is what Powerwalls can accept. Allowing for the fact that there is loss. In my case I expect three powerwalls (15kwh max) to be well matched to a Tesla 16.32Kwh system.
6. So, far, so reasonably complicated. Next, it starts to get a bit ugly. If you want Powerwalls, how much of your house to you want them to back up? This requires acquiring a rudimentary knowledge of electronics. One super basic way of starting this is to realize each powerwall can put out about 30 amps. Amps are useful because many of us understand our breaker switches. However, it is also immediately apparent that 30 amps is nowhere near enough to run an entire house with any significant electrical appliance. The accepted rule is that three or more Powerwalls truly can power an entire house. Two powerwalls could be close. The reason this is critical is that there is significant electrical engineering involved in separating the "backed up loads" from the "non-backed up loads" in a partial home back up.
7. Next, there is no way of avoiding the math. Figure out the cost of your bill, then applicable rebates, including ones for powerwalls. Its pretty likely you will be saving money regardless, but because you can pay with cash or finance, there is some relatively complex math to do to understand what you are buying.
8. By this point you would have a good idea of what you are actually going to buy for the money. Comparing Tesla to other companies for equivalent systems is next up. Tesla compares well on price, but many say that Tesla is poor on customer service.
9. Get ready for the process. Because solar and battery systems require permits from a utility, and approval of plans, they take time. During that time, if you go with Tesla (or even if you don't) there is a lot of waiting around. Plus, you need to decide where to locate stuff (panels, conduit, powerwalls, extra breakers, etc). Location by itself is a significant design decision. Tesla generates a layout of the panels very quickly. Final approval of plans takes longer.