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Solar Powered Backup vs. Propane or Natural Gas Generators

We’ve lived in rural Maine and rural New Hampshire where we’ve experienced extended power outages. Areas that are prone to Nor’esters, blizzards, snowstorms, hurricanes, ice storms, tropical storms and violent thunderstorms. Previously we’ve had propane backup generators installed.

The backup generators would come on after a few seconds when the power goes out. Although they are automatic, they have their issues. For example, we had one generator blow an oil filter and was taken back to the shop for months.

They also require weekly exercising which means they run for about 15 minutes once a week at a set time. Hopefully, you or your neighbors aren’t sleeping when it goes off because they are noisy. They also require an oil change and oil filter change after a certain number of hours used. They also only work if your propane tank is filled. If the pressure in the tank drops below a certain threshold, they don’t work. So the propane truck has to be able to get to the tank to refill it.

The gas-powered backup generators also require a spot in the yard to sit, hopefully not near a window or vent as the combustion engine gives off toxic fumes. Natural gas appliances are also major contributors to greenhouse gasses as leaks escape and emit the gas into the atmosphere. You can see this leakage every time the delivery truck comes to fill up the tank. A smell of rotten eggs is added to the gas so it can be detected.

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Gas Backup Generator vs. Battery Backup

A gas backup generator will cost you around $15K after installation, electrical work and propane tank hook-up. A battery backup generator like a Tesla Powerwall will be similar.

The gas backup generator will run until the propane or natural gas runs out. A single 10.5 kWh battery can run a house for perhaps a day before needing to be recharged.

Most outages tend to be five hours or less but for a multiple-day outage, a battery backup would not be sufficient. One would have to have a gasoline-powered generator in the garage to pull out starting with the second day.

Roof-top Solar Plus Battery Backup

A roof-top solar array allows one to replenish the backup battery and run the household on clean solar power. During a power outage, the battery provides electricity at night and then is recharged the following day, unless heavy snow covers the panels. We find that we use about 20 kWh in a typical day. One 10.5 kWh Tesla Powerwall can provide about half our usage. During an outage, conservative use of electricity can extend the limits of the single battery but many people install two Powerwalls to totally cover their usage during a power outage.

Adding solar panels creates an overall system that actually pays for itself in 10 years or less. You can’t do that with a propane backup generator.

Advantages of solar + backup battery system

  • Solar panels refill the battery the following day (unless covered by snow)
  • Silent operation
  • No oil changes
  • No weekly warm-up
  • No worrying about the tank running out of propane
  • No fumes
  • No fossil fuel use
  • No moving parts to break
  • No methane leaks
  • The switchover from grid to battery is instantaneous
  • 30% Tax rebates available
  • Power generated is used all year round (paying for itself after a number of years)
  • Extra power is sold back to the utility.
  • Costs of running is “free” as you are harvesting sunlight
  • The battery is installed in the garage or house
  • If you have an EV, you can charge at home using solar power
  • Batteries are recharged locally i.e. from the roof – no relying on fuel delivery
  • Warranties on the solar panels are typically 20-25 years and the batteries 10 years. After the warranty periods end, the systems still work, just at slightly less efficiency.
  • If you finance the system, you know what your monthly costs will be. No fluctuation of fuel prices.