Backup Generators: Is Bigger Better?

With fresh memories of Hurricane Sandy, many local homeowners are thinking about purchasing a backup electric generator. Losing power brings the hardships of no lights, no heat, no air conditioning, and in many cases, no water. Without water, your toilets won’t flush, the showers are dry, and even brushing your teeth becomes a challenge.

Backup generators come in a wide array of sizes and features. There are many small and inexpensive portable units that can run your water pump, refrigerator, and even a few lights.

Electric ranges and cooktops consume a lot of power, so a portable generator will likely be too small to help. If you have a gas-fueled range, a small generator will easily provide the small amount of power required to ignite the flame (a match will also do it).

Power needs for heating are typically relatively small, but air conditioning is another matter. The A/C compressors consume a lot of power, and would require the larger “whole house” varieties, at much higher costs.

With a “whole house” system, the big decisions are the size of the generator, and equally important, the capacity of the fuel storage system. When the power goes out in a large area, it is often impossible to get fresh fuel supplies. Pictures of long lines at gas stations after major power disruptions are all too familiar.

How big a generator do I need? This is sometimes a difficult decision, as bigger is usually better (more electrical systems will work normally). However, this decision is offset by the increased amount of fuel that bigger generators require.

Most modern homes typically have a 200-amp service entry. To provide the same amount of power, you would need approximately a 48 – 50 kW generator. This size typically uses a large (5.7L) 8-cylinder engine, which is a lot bigger than your average family car uses. Obviously, it will use more fuel than driving your car down the highway at 60 MPH.

On the other hand, a 100-amp generator (22 – 25kW) will use half the fuel, and provide plenty of power. Houses never consume all 200-amps at one time. If you exclude the non-essential, large power consumers (the sauna, steam room, electric dryer and range, etc.), 100-amps of power should be adequate to energize everything else in the house as needed.

In other words, if your stored fuel supply only gets you a day or two, the expense of a “whole house” generator might not be justified, particularly when the power is out for a week or more.

Fuel storage capacity for your backup generator is typically the biggest limitation of any system. When purchasing any backup system, make sure this aspect is not overlooked, or given too little attention.