Best Backup Power Solution: Gas Generators or Solar Battery?

Compare the Pros, Cons, and costs of Generators and Solar Batteries

The stability of power grids continues to decline. While it’s worse in some states than others right now, it’s becoming an increasing area of concern across the nation. Many homeowners and businesses are looking into backup power solutions, and this usually ends up with them trying to compare gas generators with solar battery storage.

If that’s you, then you have come to the right place. What follows is an objective comparison of the pros and cons of generators and solar batteries. Then, we’ll use an in-depth example to compare the 10-year costs for each system.

Use this list and apply it to your situation to determine your best course of action, while always keeping the goal in mind – to not lose power when the grid goes down, and to save as much money as possible in the process.

Pros and Cons of Backup Gas Generators

The advantages of gas generators include:

  • Produce more power than solar over longer periods of time
  • Power supply is stable as long as you have enough fuel
  • Flexibility in where you connect it to the grid
  • Can handle large demand with multiple horsepower
  • Easily handle it even when backing up multiple structures

The disadvantages of gas generators include:

  • Produces more power than solar over longer periods of time. (Wait a minute – wasn’t this also an advantage? Yes – see why it’s on both lists with the next point)
  • Must keep running no matter how much power is needed – energy gets wasted
  • Loud noise
  • Fuel costs
  • Fuel storage safety risks
  • Reduces air quality in the immediate vicinity and beyond
  • Requires regular servicing/repair and are subject to breakdown
  • Overall more expensive than solar batteries*

In summary, generators do well when a lot of power is needed. They can supply it consistently and reliably, even when multiple structures are in play. Generators become less efficient when less power is needed. And the fuel storage and ongoing costs and maintenance are significant disadvantages.

*See below for cost comparison

sonnen solar power battery can save your life during a hurricane

Pros and Cons of Solar Battery Storage

The advantages of solar batteries for backup power include:

  • Requires no maintenance or repair, unless you add on a manual generator for emergency power regeneration
  • Unlimited supply of energy from the sun – no fuel to purchase or store
  • Quiet
  • Has minimal negative impacts on air quality or environment
  • Costs less than generators*
  • Only powers what is needed – highly efficient

The efficiency advantage of a solar battery is significant. Unlike a generator which must always be on no matter how much power is needed, the solar battery will only use whatever energy is required in a given moment.

For example, suppose your grid goes out in the heat of summer, on a weekend when everyone is home. Now your backup power supply has to power your air conditioning, in addition to everything else in your house. That is a very different situation than if it’s a pleasant 70 degrees outside, the kids are in school, parents are at work, and the only power required is for basic systems like the hot water heater and the fridge.

In each of those scenarios, the generator must be on the whole time or your fridge and freezer will thaw. So all that gas is being used just to keep your freezer on. But the solar battery will hardly use any power in that scenario, because hardly any is required of it.

The disadvantages of solar batteries for backup power include:

  • Can ‘run out’ of power if demand is high and extends for many days
  • Struggles to re-supply itself in certain weather conditions, such as nighttime (solar actually can work even when it’s cloudy, just not as well)
  • Not quite as practical for large scale situations

10-Year Cost Comparison Between Gas Generators and Solar Battery Backup

A solar company in California, which has fielded a lot of business for solar batteries because California has been going crazy with grid blackouts the last few years (14 days in 2019!), did an in-depth cost comparison between generators and solar batteries.

It’s just one comparison, so it obviously does not apply to every situation. As stated already, for larger scale systems, the cost comparison would need different numbers. This comparison is for a typical home-sized or small business system.

They compared a 20kW propane generator – based on a real quote from a customer of theirs – with a sonnen Eco 12.5kWh battery.

Their comparison assumes you would need your backup power solution for 10 days per year, which seems a reasonable estimate.

Here’s the breakdown:

Propane Generator Costs

Upfront cost, which includes the generator, the transfer switch, the installation and the permits, comes to $13,500. This estimate did not include a pad for the generator to sit on, or a propane tank or a hookup to the tank. Now, you don’t have to use propane, but you will have to find some way to store whatever fuel you choose to use. There’s a cost to that. For this, the propane tank (and propane accessories) adds $1500 to the cost.

Thus, they estimate you would pay about $15,000 up front for a propane gas generator.

What about ongoing costs?

This particular generator burns 3.45 gallons of propane per hour, which is about 83 per day. At $2.50 per gallon, that’s about $200 per day just to use the generator. Assuming 10 days per year, that’s $2000 per year in fuel costs, and $20,000 over a ten-year period.

Let that sink in – you could spend $20,000 in fuel alone for a gas generator if you use it just ten days per year.

With an additional estimate of $1000 in repair and maintenance in years 6 and 10 – assuming no serious problems – the total 10-year cost of a gas generator comes to $36,000.

Solar Battery Storage Costs

The sonnen solar battery sells for about $30,000. Certainly not cheap. However, if you buy the battery when you buy your solar array too, you get to apply the federal tax credit known as the solar Investment Tax Credit to the purchase. In 2020, that credit gives you a 26% savings.

So, that $30,000 cost reduces to $22,200 once you do your taxes the following year.

You will also save money because of the efficiency we talked about earlier, and because the battery will also supply extra power during normal situations too. In other words, even when the grid is on, your solar battery can supply power to your home or business. If this happens during high cost, high usage periods like the evening, your battery will save you money because you won’t be using the much more costly power from the grid.

The solar company doing this estimate assumed about $500 per year in savings from the increased solar efficiency provided by the battery. You can get more details of their rationale for this here.

That’s an extra $5000 in savings, bringing the 10-year cost for solar battery storage down to $17,200. That’s less than half the cost of generator.

What’s important about this is, even if their estimates are way off, there is nearly a $20,000 difference in costs. So even if their estimates are wildly off base and it’s “only” a $10,000 difference, that’s still a $10,000 difference!

Again – there are pros and cons to both solar batteries and gas generators. But cost is on the side of the solar, and hopefully now you understand why. Put another way – with solar batteries nearly all the cost is up front, and you will recover some of that investment over time. With generators, you will never stop paying for it. And it stinks, makes noise, and fouls the air.

If you want to inquire about solar battery backup for your home or business, click below to get a quote and a free solar consultation.

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