Power Outages and Self Generation

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Update: Power was restored at 11:00am on the 31st for an approximately 28 hour outage.

At 7:16am Wednesday October 30th, SDG&E proactively cut power to about 1,000 RSF customers including half of the Village, the Golf Course, and most northern and eastern residents. Southwestern residents were not affected. The SDG&E outage map says that the outage is expected to last until 6pm October 31st, meaning that power will be out for about two days. Last year, a portion of San Marcos was without power for six days.

Given that the reason for such outages (Santa Ana winds, aerial transmission lines, and a cautious utility that doesn’t want to get sued into bankruptcy like what is happening to PG&E) isn’t going to change for many years, it is safe to assume that this is the new normal and we should protect ourselves accordingly. 

Following is a how to guide on how you can generate your own electricity for these kinds of situations.

Whole House or Critical Load?

When designing a backup power solution, you initially have a choice of whether to provide emergency power to your entire house, or only to some critical loads. Your battery or generator could be much smaller if you designed your system to only power certain loads during a power outage. For instance, you could choose to just power:

  • Refrigerator, freezer
  • Gates
  • Some Lights
  • Instant hot water heaters
  • Internet connection and office 
  • Alarm/Security
  • Stove/Oven
  • Bedroom Air Conditioners or, in winter, heaters

When you gather such a “critical load” list, especially if you consider the power outage could be several days long, it could end up being rather long. Another issue is that as your house gets larger, you end up with more and more electrical subpanels. Critical loads could be spread among many subpanels and extracting these loads out and powering them from a single critical load panel may not be easy. For these reasons, I am assuming below that you will opt for a whole house backup system.

Solar + Battery

Solar panels can be an effective way of generating electricity but they will not work during a power outage unless you also have a battery system. Solar panels just by themselves turn off during a power outage.

Tesla and others make battery backup systems that integrate with solar panels. If you have a modest sized home (around 4,000 sq ft and under), this solution can work well. During the day, the solar panels power your home and charge your batteries, and then you use battery power overnight. However, you must make sure your have enough solar panels and enough battery storage to last days. 

40 panel, 13 kW ground mount solar system

For example, I helped a friend install a 13 kW solar panel system for his 4,100 sq ft house. They have no children (so power needs are more modest), and their solar panel system generates just enough electricity to cover their usage over the course of a year. To do this, they needed a 40 panel ground mount system (just putting panels on the roof would not have been enough).

To give him reliable backup power to last days, he would need at least three Tesla Powerwall batteries, at a cost of about $20,000 plus installation.  See below, but an equivalent generator would cost about $5,000 plus installation.

Once you get to larger estate sized houses, solar+batteries become impractical. The amount of solar panels needed would cover a good sized field, and your batteries would be very expensive.

In operation, a solar + battery system appears seamless when the power goes out. Computers might reboot during power transfer, but battery power will be supplied within a second of the outage.

Generator

20kW generator for houses up to 5,000 sq ft.

A generator is an engine (similar to a car engine) that uses combustible fuel (gasoline, propane, natural gas or diesel) to generate electricity. They are sized according to your peak power needs. 

Houses up to about 5,000 sq ft can use a 20 kW generator. This is the sweet spot for pricing with many different manufacturers selling units in this size range at around $5,000. 

A whole house generator is installed by a contractor/electrician. It is typically powered by either natural gas or propane. If you use propane, you might need to increase the size of your propane tank to handle long outages. 

48kW generator suitable for a large estate house

Larger, estate sized houses will need a 30 kW or larger generator and those are priced in the $10K to $20K range.

These generators will start after the power has been out for about 10 seconds. They will automatically shut down once power has been restored by the utility.

Generators are noisy. Think of a fairly loud car engine. To hear one in operation today or tomorrow, head to the top of the golf course top parking lot and listen to RSF Connect’s generator running. One thing you can do to reduce noise is to buy a slightly more costly generator that runs at 1,800 RPM instead of the standard 3,600 RPM. Whole house generators will typically automatically run an “exerciser” cycle once a week for about 10 minutes to ensure the engine is ready for an outage. Expect to have your generator serviced every few years (oil change, spark plugs, starter battery, etc). 

Generator Installation

Installation is somewhat complex and should be handled by a contractor. Click here to watch a 13 minute video of a contractor installing a 22 kW generator for a suburban home.

The first thing you need to do is get CDRC approval. While the CDRC won’t disallow generator installation, they may require noise screening depending on placement (typically a stucco’d concrete wall). 

Generators are typically placed near the main electrical panel and near a power source (natural gas line or propane tank). You can place them anywhere, but it might mean a longer electrical conduit or fuel pipe. 

The most complex part of the installation is configuring the electrical panel. You will need an additional panel called an Automatic Transfer Switch (ATS) near your main electrical panel. Homes that have a 200A main panel are relatively easy to integrate with a generator. If you have a 400A or 600A panel (or, like me, you have a funky 400A split panel that is a 200A panel plus a 150A breaker offshoot), then it becomes more complicated. Ask lots of questions from your contractor about where the ATS panel will be located, how it will be mounted, etc.

Conduit and fuel line piping will need to be run to the generator from the main panel and fuel source.

While most electricians can install a generator, you will also typically need a plumber for the fuel piping, and maybe need general construction for a wall, stucco, etc. A general contractor might be appropriate for a larger job, or use a manufacturer’s dealer for more straightforward installations. 

One local resident recently installed a large 48 kW generator and had his handyman do the trenching and electrical conduit, while the dealer (OC Generators) did the electrical work, plumbing and generator installation. 

The two main generator manufacturers are Generac and Kohler. Click on their dealer locators in their web sites to find an installer/dealer. 

Sizing

Here are two ways of doing a back of the envelope calculation to determine how big a generator or battery system you need.

First, some terminology. The amount of electrical power you are using at any one instant in time is denoted in watts, but the specific unit we use for household power is in units of 1,000 watts, or kilowatts, abbreviated kW. The other unit is called kilowatt-hours, abbreviated kWh and is used to measure how much total energy you’ve used over a period of time.

All the numbers shown above are in kW and thus tell you how much power the generator/battery/solar can output at any one point in time. Basically, you need to size your generator/battery so that it can output more power than your peak power usage.

SDG&E meter showing house using 7.206 kW of power

One method of determining peak power usage is to look at your SDG&E meter when you’ve got all your AC units humming, lights on, cooking a meal on your electric range, drying clothes in your electric dryer, etc. Your SDG&E meter cycles through a lot of information, but every 30 seconds or so, it shows current power usage in kW. Here’s a video I just took of my SDG&E meter that shows this.

You want to do this test when you’ve intentionally turned on as many appliances and AC units as you think is reasonable to get an accurate reading of typical peak power usage. And then give yourself some headroom. So if your peak power reading is 20 kW, maybe look for a 30kW or bigger generator. 

Another way to determine peak power usage is through the SDG&E online energy usage portal. For that, you need to have an online account with SDG&E. Once in the main screen, click the My Energy Overview menu entry under the My Energy menu. Give it some time, their web site is slow.

Then click the My Energy Usage link on the bottom left. This will pop up a graph of total energy usage each day for the past month. Look for a day where you used the most energy. You can also go back a month at a time to find other high usage days. Pay attention to the vertical axis as it rescales for every month or day it displays. So click on a high usage day and the system will then show you total energy usage for that day broken down into 15 minute increments. 

For example, here’s a high usage day for me:

Total energy used during each 15 minute increment.

So sometime around 9:15am, I used around 6 kWh of total energy during a 15 minute period. Multiply this by 4 to find out what the average power usage was during that 15 minute time period (Why 4? Exercise left to the reader). So, on average, I used 24 kW of power during that 15 minute interval. This means that sometimes I used less than 24 kW and sometimes I used more. How much more, which is what I really want to know? You can’t tell from this data. Multiply it by 1.5 to get a back of the envelope estimate of me needing at least a 36 kW generator to handle my peak load. 

RSF Connect

Incidentally, RSF Connect is working fine during this power outage due to their propane powered generator. Since this was their first power outage, something had to go wrong, and a piece of equipment that wasn’t quite up to the task this morning failed. So RSF Connect was down for about an hour until Race technicians diagnosed the problem and replaced the faulty piece of equipment. 

Of course, only people that have generators or battery systems at their house can continue to use the Internet…

Summary

With a fairly modest investment ($8K – $25K, including installation), you can equip your house with trouble free whole house electricity backup. Given the new normal of fairly frequent multi day blackouts whenever the Santa Ana winds blow, I would recommend people look into backup power if you live in the part of Rancho Santa Fe that is getting these blackouts. If you’re like me and live in the southwestern portion, you might get by just by crossing your fingers…

Click here to discuss this topic, ask advice, trade installation or operation war stories, etc.