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Verified Reviews for Generator Install pros in Grantham, NH

*The Angi rating for Generator Install companies in Grantham, NH is a rating based on verified reviews from our community of homeowners who have used these pros to meet their Generator Install needs.

*The HomeAdvisor rating for Generator Install companies in Grantham, NH is a rating based on verified reviews from our community of homeowners who have used these pros to meet their Generator Install needs.

Last update on May 01, 2025

Find Generator install pros in Grantham

Avatar for Vermont Generator Systems
Vermont Generator Systems
5.0(
1
)

Serving Grantham, NH and surrounding areas

Approved

In business since 2008

Free estimates

Emergency services offered

Since 2004, Vermont Generator Systems has proudly supported the backup power needs of homes and businesses across parts of Vermont and New Hampshire. Our experienced team is with you every step of the way, from the initial site assessment to professional installation and ongoing maintenance. VGS has deep expertise in installing and servicing Generac generator systems.

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Response time6 hrs
27 neighbors recently requested a quote
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Richard Hebert Master Electrician
5.0(
1
)

Serving Grantham, NH and surrounding areas

Approved

In business since 2020

Credit card accepted

Offers commercial services

We can take on a wide range of residential and commercial electrical projects to include full installation for additions and remodels as well as wiring/panel upgrades, and a variety of other projects. We take pride in the quality of our work and our commitment to outstanding results. We look forward to building strong, long-term relationships with our clients and guarantee your satisfaction.

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Levi Electric
New to Angi

Serving Grantham, NH and surrounding areas

Approved

Free estimates

Emergency services offered

Warranties offered

Levi is a Master Electrician with over 10 years of experience in the electrical trade. He has primarily worked in high-end residential and custom homes, bringing strong expertise in electrical layout, lighting design, and coordination with insulation and building systems. Levi is highly knowledgeable in all aspects of residential electrical work, from rough-in to finish, and is committed to safe, code-compliant, and high-quality installations.

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Avatar for JM Electric LLC
JM Electric LLC
4.5(
26
)

Serving Grantham, NH and surrounding areas

In business since 1989

Free estimates

Emergency services offered

"The amount of work that needed to be done to our 1880 house was extensive. Joe listened to our needs and concerns and offered suggestions that improved our plans. His quote was very fair. He is easy to talk to, professional and honest. Caleb and Dylan who did the work were amazing to deal with. They were very knowledgable, worked hard, and were careful and patient dealing with the oddities of an old house. I highly recommend this company and will call on them for all my electrical needs."
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+15

Recommended by100%of homeowners
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NH Generator Installers, Inc.
New to Angi

Serving Grantham, NH and surrounding areas

In business since 2009

Free estimates

Credit card accepted

About NH Generator Installers (formerly Corr & Son's Electric) - Concord, NH\n\nNH Generator Installers is a team of motivated team members dedicated to providing top-quality power generator installations at competitive prices, including home generators and commercial electric generators. We are a professional, reliable, hard working generator distribution and installation company that takes pride in completing all jobs accurately and in a timely manner. \n\nWe are committed to establishing long lasting relationships with our customers by exceeding expectations, gaining trust through exceptional performance, unparalleled service, and honest and ethical business practices. We recognize that teamwork is essential in order to achieve successful project completion.\n

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Avatar for Southridge Electrical Contracting LLC
Southridge Electrical Contracting LLC
5.0(
3
)

Serving Grantham, NH and surrounding areas

In business since 2022

Free estimates

Emergency services offered

"They were fast and responsive to what we needed. I will bring them back again. They were very professional and cleaned up well."
Response time1 day
Recommended by100%of homeowners
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Generator Install questions, answered by experts

No, you should never plug a generator directly into a wall outlet in your house. This practice is extremely dangerous, often illegal, and can cause "back-feeding," where power from the generator flows back into utility lines, creating a life-threatening hazard for utility workers. It can also damage your home's electrical system, including appliances like pumps and HVAC fans. If the main power is restored while the generator is connected, it can destroy the generator and cause an electrical fire. To safely connect a generator, you must use a professionally installed transfer switch or an interlocking kit, which prevents back-feeding by disconnecting your home from the utility grid before the generator provides power.

To determine the right size generator for your house, you should calculate the total wattage of the appliances and devices you want to power during an outage. List all essential items, note their start-up wattages, and add them together.

Here are some typical wattage requirements for common appliances:

  • Refrigerator: 600 watts

  • Large dehumidifier: 700 watts

  • Large window air conditioner: 1,400 watts

  • Water heater: 3,000 to 4,500 watts

  • Electric furnace: 5,000 to 25,000 watts

A 7,500-watt generator might be sufficient for essentials like a refrigerator, freezer, well pump, and lighting circuits. However, for high-demand items like a water heater or furnace, a whole-home generator is a better choice. A portable generator may be enough if you only need to power a few critical items.

While home square footage can offer a rough estimate, it is not always a reliable indicator. For reference, here are some typical generator sizes based on square footage:

  • 1,000 sq ft: 6–9 kW

  • 1,500 sq ft: 7–10 kW

  • 2,000 sq ft: 10–14 kW

  • 2,500 sq ft: 12–16 kW

  • 3,000 sq ft: 16–20 kW+

For the most accurate sizing, consult a professional who can calculate your home's peak and average power consumption and recommend the optimal generator.

The cost to install a whole-house generator averages $5,200, with a typical price range of $1,500 to $8,900. However, total costs can vary from $400 for a small portable unit to over $18,000 for a large-capacity system. The most significant cost factor is the generator's size and capacity, but other variables include the brand, fuel type, and labor for assembly and installation.

Generator costs can be broken down by type:

  • Portable or Emergency Backup Generators (1kW–7.5kW): $500 to $2,000

  • Partial-Home Generators (9kW–20kW): $2,000 to $6,500

  • Whole-House Generators (22kW–48kW): $5,000 to $18,000

To avoid paying for more power than you need, consider hiring an electrician to calculate the electrical load for your essential appliances. It is also recommended to get at least three quotes to find the best deal for your specific needs and budget.

Yes, in some locations, it is required by the National Electric Code (NEC) to have a transfer switch installed for electrical emergencies. In addition to following electrical code, generator transfer switches ensure your home is fully protected during a power outage. By switching the power from the main breaker to the generator breaker, you can seamlessly operate your HVAC, lights, appliances, devices, and more during an emergency. 

The amount of time a standby generator can run continuously is around 3,000 hours on average. However, standby generators can generally run indefinitely as long as they have a continuous fuel supply. Generators hooked up to a home’s natural gas supply are the best option for extended usage, as these won’t rely on a finite fuel supply based on how much you have in storage. Generators running on liquid propane or diesel won’t last as long, as these require fuel storage and regular refueling to stay running.

The Grantham, NH homeowners’ guide to generator installs

From average costs to expert advice, get all the answers you need to get your job done.

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