What is a solar system really?A solar system is basically just a generator that produces electricity measured in kilowatt hours. This is always shown abbreviated as kWh.

So what is a kilowatt hour?1 kilowatt equals 1000 watts. Remember the old 100 watt light bulbs? Take ten of those bulbs and turn them on for 1 hour. That would be 1 kilowatt hour (1kWh). This is how PG&E bills you: by the amount of kWh’s you use in a month.

x1 hour = 1kWh

How does PG&E charge?Residential customers are charged in 4 tiers. Each tier is allotted a certain amount of kWh’s. When you have used all the hours in that tier, you move up to the next. You start out in tier 1 and as you use more power you climb up to tiers 2, 3 and 4. Tier 1 rates are about 15￠ /kWh, tier 2 rates go up to about 19￠ /kWh. Tier 3 gets much higher at 32￠ /kWh and finally tier 4, a whopping 35￠ /kWh.

How does net metering work?It’s pretty simple actually. When the sun is shining and your solar system is producing more power than you’re using, your meter spins backwards, giving you credits in kWh’s. When the sun goes down, or on a cloudy day, the meter spins forward, and you’re charged for those kWh’s. Instead of being billed every month you will get a true up statement at the end of the year. If you use more kWh’s than you generated, you’ll owe the balance to PG&E. If you produce more than you use, PG&E will give you credit at the rate of 5￠ /kWh. PG&E will still charge you a base fee for connection to their grid. These fees are usually about $4.50 - $5.00/ month for residences.

Roof mount vs. ground mount systemsRoof Mount: Generally cost less than a ground mount. Composition shingle roof installations are the cheapest, while tile roofs - especially Spanish tile - are more expensive and require more care. Be sure that only a certified roofing contractor drill holes in your roof! If your roof needs to be replaced, do it before installing solar. When a roof needs replacing, the solar panels must come off and then be replaced afterward.

Ground Mount: Easier to keep clean. More expensive due to trenching, digging holes, pouring concrete, and higher labor costs. A good solution if you don’t have a decent roof to mount panels on or you just don’t like them on your roof.

How to size a solar systemThere is no financial incentive to produce more power than you use. PG&E only pays 5￠ /kWh for excess power produced. Therefore, you don’t want to overbuild your solar system.For those with higher PG&E bills (over $200/month), you’ll get the most bang for your solar buck by eliminating tiers 3 & 4 because those rates are so high. It becomes less cost effective to eliminate tiers 1 & 2 because you are being charged a lower rate. For example let’s say 10 panels saves you $120/month in tiers 3 & 4. Those same 10 panels will only save you $60/month in tiers 1 & 2.

What is an inverter?Solar panels produce DC electricity that needs to be converted to AC. That’s the job of an inverter. There are two types of inverters, string inverters and micro-inverters.

What is a string inverter?String inverters are a single unit that converts the power of many panels. They act like Christmas tree lights; when one light in the string goes out, the rest of the lights in front of it go out. If a panel gets shaded, has an obstruction, or fails, it affects other panels on the string until the condition is resolved. There are companies like SolarEdge who sell string inverters with power optimizers that control each panel separately, eliminating the “string” issue. String inverters usually have a lifespan of 10-15 years and will need to be replaced at least once during the life of a system.

What is a micro-inverter?These small inverters are mounted behind the solar panel. Each solar panel gets its own micro-inverter and becomes independent of the rest. This means if one panel is shaded, it does not affect any other panel in the system, which increases efficiency. Micro-inverters convert the DC at the solar panel which eliminates the need for high voltage DC wires on your roof, making it a safer solution. Micro-inverter systems are usually a little more expensive than string inverters but they come with a 25 year warranty.

What is online monitoring all about?Most solar systems sold today include some sort of online monitoring. Systems using micro-inverters or power optimizers allow you to see how much power your system is generating - at any given moment - on your computer, tablet or smartphone.

Online monitoring alerts the installer if there is an issue with the system and allows them to diagnose the issue over the computer.

Does a solar system require maintenance?

A couple of points to consider:If you’re using a string inverter, at some point it will need to be replaced. If you need to replace your roof in the future, the solar panels will have to be removed and put back in place afterward. If your roof is old, it’s best to have it replaced before installing a solar system.Solar Panel Maintenance

Specialist

That’s one of the beauties of solar - there really is no maintenance involved other than occasionally hosing off the panels or keeping them clean in general.