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.
Will my electric bill go to zero if I install solar?
No, there is still a minimum fee of around $15.00 per month for Duke Energy customers.
How much will a solar system cost?
The installed cost of an 10kW system should be around $25,000. ($17,500 after the Federal Rebate of 30%.)
The installed cost for a solar system is usually between $2.00 and $2.75 per watt. This means that an 10kW system should cost between $20,000 and $27,500. There is currently a federal rebate of 30% for most customers.
Some things that may increase your cost per watt:
Extremely High efficiency panels
Smaller system size
Difficult roof access
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 so tat the monthly payment on the solar loan will be less than the previous power power bill.
Installing solar also insulates you 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 years or more. 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, and they will run your home for about 12 hours.)
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 (2021 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.