How Much Does a Whole House Generator Cost

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How much does it cost to add a whole house generator?

Another storm, another power outage. You tread through the mud and make your way to your shed. You start digging through your things to find your portable generator and your power cord. In the rain you wheel it out and hook it up to your inlet box. You pull and pull the cord but it just won’t start. Is the gas still good? Maybe it’s the spark plug? You were too busy this year and forgot to get it ready for the unpredictable event of an outage. Now you’re wondering what to do next or how to get it running while your family sits in the dark waiting for you to find a solution. At this moment you tell yourself: I’ve got to look into a whole house generator.

-What SIZE generator do you need?

A generator is sized by the power (wattage) that you need. Having a 200 amp service is very common in our area, but this doesn’t necessarily mean that you use all 200 amps available. Basing our calculations on the size your home as well as the quantity and size of your appliances, we’ll determine the correct generator size required for your home. A generator in the range of 20 – 24KW will often be sufficient.

-What’s the COST of the generator and installation?

It depends. We’ll need to purchase the generator along with the battery and a 2” concrete pad. If you live in a flood zone, we recommend setting generator on a raised platform away from potential flood damage. Installation of the generator, gear and wiring will be between $3,000 – $5,000, price affected by the distance from generator location and electrical service. We will also need to provide either Liquid Propane (LP) or Natural Gas to run your generator. If you live on a slab or if your electrical panel is near the garage, we may need to include some money in the budget to repair sheetrock and touch up paint. If you’d like Oak Electric to handle everything with this project, turnkey price is typically $12,000 – $15,000.

-How does the installation PROCESS go?

Ideally, setting and wiring the generator is a two day process. First, the generator and ATS location is decided and both are mounted and set. Two conduits are installed: one for power and one for communication. These are ran, wire pulled through and terminated. All piping necessary for the Liquid Propane or Natural Gas to feed the generator are also ran and connected at this time (this means no more having to drag out gas cans to fill your generator). At this point, inspections are to be done for both the electrical and gas installation. After the inspection has passed, power is shut off momentarily to your home to tie the generator into your electrical service. This should take about an hour, with a few power blips for testing after power is restored. After this step, we perform the start up procedure on your generator to bring it online and working with your service.

-Any MAINTENANCE on my generator?

As with any engine, avoiding maintenance can mean a very costly repair in the future and will void your warranty. To keep your generator in top shape and ready for any emergency, it is recommended to change the spark plugs, air filter, oil and oil filter once a year. It may also be necessary to change your battery if it’s no longer holding it’s charge. The MobileLink App makes it easy by sending notifications to your email from your generator and will let you know when it is time for regular maintenance.


Turnkey Price for items directly associated with generator project: average $12,000 – 15,000

Maintenance costs (spark plugs, air filter, oil & oil filter change): $250 per year

Disclaimer: This article focuses on the cost of adding a STAND BY generator with an Automatic Transfer Switch. There is a significant price difference between a portable generator on wheels that must manually be connected versus a stand by generator that automatically turns on when it detects a power outage. Prices and details displayed in the article are based off of the 2021 Generac Master List, a brand with a great reputation.