A typical house will need about 10kW (roughly 30 panels) if you want to produce all of your own power.
Solar systems are usually sized so that they produce enough power to equal your average electrical bill. Some months you may produce more power than you use, and some months you may produce less.
It is not a good idea to produce substantially more power than your average monthly usage because the power company pays a very low rate for the excess power that you generate.
How much money will this save me on my electrical bill?
A typical 10.0kW system will save you around $200/month on your electric bill.
Here in St. Petersburg, we have the equivalent of about 5 hours of direct sunlight a day. This means that a 10kW system will produce 50kWh per day. Over the course of a month, you will produce about 1500kWh. If your electric company charges 13 cents per kWh, this will save you $195/month on your electric bill.
How much will a solar system cost?
The installed cost of an 10kW system should be around $25,000. ($18,500 after the Federal Rebate of 26%.)
The installed cost for a solar system is usually between $2.00 and $3.00 per watt. This means that an 10kW system should cost around $25,000. There is currently a federal rebate of 26% which reduces this to $18,500.
Some things that may increase your cost per watt:
Smaller system size
High efficiency panels
Some things that may decrease your cost per watt:
Larger systems size
Standard efficiency panels
What is the payback period for a solar system?
It will usually take around 8 years to save enough money on your electric bill to equal the full sytem cost. However, with financing, many people can start saving money from day one.
Many customers will finance their solar system. A typical loan might be for 15 years at 6% interest. The monthly payment on the loan ($156) would be less than the money you are saving each month on your power bill ($195).
You are also insulated from any increases in the cost of energy from the electric company.
Finally, after the loan is paid off, you own the solar system outright.
How long will a solar system last?
Solar panels are usually warranted to produce at least 80% of their original power rating for a period of 25 to 30 years. The panel life is probably much longer than that. The power electronics (we typically use micro-inverters from Ehphase) are warranted for 25 years.
Should I install batteries with my system so that I can go off-grid?
No. We do not feel that batteries are financially beneficial yet.
Here are some reasons why we think batteries are not a good investment yet:
1. The state of Florida has net-metering laws that require the power company to let you use the electrical grid as a free battery.
2. Batteries are still quite expensive. (For example: Installing two Tesla PowerWall battery costs about $18,000 after installation. Competing products from Enphase and SolarEdge are even more expensive.)
3. Batteries degrade over time, and will need to be replaced periodically.
4. Battery technology is still improving rapidly, and the next generation of batteries looks to be much longer lasting.
Will my solar panels run my home when the power is out?
Not unless you install some very expensive batteries. Click details for some upcoming options.
A traditional gas-powered generator is probably the best choice for power outages today. We believe that there will be some better options in the very near future:
Enphase has announced that their IQ8 micro-inverters (2020 release date) will provide power during an outage.
If you own an electric car, then you might be able to purchase a Vehicle-To-Home charger that lets your car power your home during a power outage.
Finally, battery prices are falling quickly, and they should be a viable solution for power outages in just a few years.