The pad is poured, the electrical is tied into the panel, and the plumber has already come out to run a new line from your gas meter to your generator site. This is sure to be a glorious day commissioning your brand new natural gas generator. But there's still one major obstacle still standing between you and having a reliable backup (or prime power) generator ready to deploy: the natural gas utility. Interconnection with a gas utility varies with every utility, but there are a few key guidelines to follow to ensure that interconnection goes quickly and you stay on the utility's good side:

1. Know the Demand that You're Demanding

The gas utility's biggest concern for tying your generator to the system will come down to one question: how much demand will the generator put on the utility's system. This should be readily available with your generator's specification sheet, but there are ways to get close to answering this question without a specification sheet. A conservative way to approach this problem would be to use a heat rate of 15,000 Btu/kWh. Multiplying that by the generator's kW output will provide a conservative estimate for the demand. For example, a 100 kW generator might demand 1,500,000 Btu/h.

The specification sheet will ultimately be a better method to determine the demand, but make sure that any heat rate specifications in the sheet are converted from Low Heating Value (LHV) heat rate (which is typical of a spec sheet) to a High Heating Value (HHV) heat rate by multiplying the LHV heat rate by 1.11.

2. Pressure to Perform

Almost as concerning is the pressure required to operate the generator. The generator will have a pressure regulator near its fuel inlet which will drop the pressure from the line pressure to the pressure that ultimately is compressed into the engine. The generator should list a minimum (and maximum) pressure that can be used. Typical neighborhood natural gas distribution lines operate at 60 psig or below. From the line pressure, it will be reduced a bit due to normal pressure drop through the system, then drop from the pressure cut across the pressure regulator at your property and another drop in the line between your meter and the generator. This series of pressure drops can limit available generator inlet pressure to no more than 5-10 psig from a typical distribution system without having to interconnect with the utility's high pressure system; increasing complexity and cost of the project.

Ultimately pressure and load will act in tandem; the utility may be able to provide more demand if the pressure requirement is lowered and vice versa.

3. Lead by Example

Every project is under pressure to get done quickly and on-time, but the more lead time you can provide the utility the better. Even if the project is only conceptual, there's no harm in reaching out to the utility to see if they can meet the demand and pressure requirements of the project. Large enough generators will require the utility to model running the generator during times of peak demand to ensure that the generator's load won't adversely affect other customers.

Additionally, your utility sales/marketing person will be able to give you an idea of their current workload for adding new customers, provide some perspective as to how the process of interconnection works and, most importantly, provide an estimate for how long the interconnection process will take.

When reaching out, be sure to ask if there are any special utilities rates or incentives available specifically for natural gas generation. If you're able to take your project one step further and install cogeneration (taking waste heat from the generator for use in another on-site process), further incentives or special rates may also be possible. Natural gas distribution utilities welcome these sorts of load additions because they often require gas in the summer time; a time when other natural gas demand (and therefore revenue) is low.

So fear not the utility; your goal of generating (backup or prime) power just so happens to line up perfectly with the utility's goal of selling natural gas. Good luck on your project and happy generating!

This article was brought to you through a joint effort by Warren Good, Affordable Generator and Power Systems and Anthony Cadorin, PE, MSME, DGCP, Veritas Energy Analytics, LLC.

Veritas Energy Analytics is a rapidly growing company specializing in natural gas demand modelling and planning for utilities, consumers and more.