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    Verified generator installs reviews

Top-Rated Generator install pros in Derwood - Updated Nov 2026

Long Electric, LLC
5.0(
174
)
Fixed Generator - InstallGenerator - Install - For Business

Serving Derwood, MD and surrounding areas

Approved

Super Service Award Winner

In business since 2010

Free estimates

Customers say: Quality work

"My experience is getting a new whole house generator installed by Long Electric was wonderful. They were responsive, timely and very professional. Everyone I dealt with was very courteous and answered all my questions over and over. I highly recommend their services."
Response time2 days
7 neighbors recently requested a quote
Recommended by87%of homeowners
Avatar for Rollins Repair
Rollins Repair
4.7(
56
)
Fixed Generator - RepairGenerator - Repair - For Business

Serving Derwood, MD and surrounding areas

Approved

In business since 2004

Free estimates

Credit card accepted

"Our existing generator died. James diagnosed the problem and gave us a few options to repair or replace it. We chose to replace it. James handled everything, from getting and installing the new generator to electrical and fuel (propane) connections. We have asked him to schedule us for the annual maintenance on the machine. We are pleased, though we haven't lost power since it was installed, LOL."
 Air Cooled Generator
 30KW Quitesoure
 Residential Installation
 20KW Air Cooled
 Another Residential Installation

+6

Response time9 hrs
2 neighbors recently requested a quote
Recommended by97%of homeowners
Avatar for Bailey & Shipp Electric
Bailey & Shipp Electric
4.1(
82
)
Fixed Generator - InstallFixed Generator - RepairGenerator - Install - For Business+1 more

Serving Derwood, MD and surrounding areas

Approved

In business since 2011

Free estimates

Emergency services offered

"Your technician that came out to do a yearly maintenance inspection on my generator was very nice and knowledgeable. He arrived actually earlier than expected and went right to work. I would recommend your company to anyone and it was so nice to deal with someone who acted like they enjoyed their work and wanted to please. Thank you!"
3 recessed lights
Single Recessed Light
Custom Bathroom Wiring
chandelier
Panel Replacement After

+8

Response time10 hrs
5 neighbors recently requested a quote
Recommended by91%of homeowners
Avatar for Artisan Electrical LLC
Artisan Electrical LLC
4.6(
21
)
Fixed Generator - Install

Serving Derwood, MD and surrounding areas

Approved

In business since 2020

Free estimates

Credit card accepted

"Very friendly from the technician to the secretary. They got me in fast worked with my schedule and got out fast. They also mounted my ring doorbell.. Excellent service and the price was awesome"
Fixed Generator Install
Fixed Generator Install
Fixed Generator Install
Fixed Generator Install
Fixed Generator Install

+2

Response time1 day
9 neighbors recently requested a quote
Recommended by68%of homeowners
Avatar for One Source, LLC
One Source, LLC
4.8(
6
)
Fixed Generator - InstallGenerator - Install - For Business

Serving Derwood, MD and surrounding areas

Approved

In business since 2014

Free estimates

Emergency services offered

"I had John and Aaron come to my home because I was interested in installing a Theater in my new home. They went through the new technologies and options for the Theater and were very knowledgeable. I ended up going with a 4K projector and a Dolby Atmos and absolutely love it and show it off to all my neighbors. Iâ m so glad I took their recommendation on spending the extra money on the projector to get true 4K. I watched the Pitt game this weekend in 4K and it was amazing. I totally recommend this company."
After!
Proper Grounding Showcase
Theater Screen with Starry Night Ceiling
Before!
Lighting Fixtures in a restaurant

+26

Response time2 days
Recommended by80%of homeowners
Avatar for Horizon Services, LLC (MD)
Horizon Services, LLC (MD)
3.8(
1,464
)
Fixed Generator - InstallFixed Generator - RepairPortable Generator - Install+1 more

Serving Derwood, MD and surrounding areas

Approved

In business since 1989

Free estimates

Emergency services offered

Horizon Services (MD), LLC, is the regions largest and most well respected plumbing, heating and air conditioning company, with nearly 600 employees serving tens of thousands of homeowners throughout Delaware, Southeastern Pennsylvania, Southern New Jersey and Northeastern Maryland. After a quarter of a century in business, Horizon Services (MD), LLC, remains fully committed to setting the industry standard for customer service, installation and focusing on things that are important to busy homeowners.

Recommended by89%of homeowners
Calvert Generator
New to Angi
Generator - Install - For Business

Serving Derwood, MD and surrounding areas

Approved

In business since 2021

Free estimates

Credit card accepted

Calvert Generator is committed to excellence in every aspect of our business. We uphold a standard of integrity bound by fairness, honesty, and personal responsibility. Our distinction is the quality of service we bring to our customers. Accurate knowledge of our trade combined with ability is what makes us true professionals. Above all, we are watchful of our customers' interests, and make their concerns the basis of our business. \n

Response time10 hrs
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Generator Install FAQs, answered by experts

In many cases, yes. There are models called dual-fuel generators and fuel switches, but only between certain types of fuel. For example, with the right setup you can convert a generator from natural gas to propane. Some allow switching between diesel and gasoline. There are even tri-fuel generators available in some cases, which adds a large layer of security if you are worried about fuel availability in times of crisis. Always check your generator capabilities and manual instructions before trying to switch fuels. Some generators can use another fuel but may need a fuel conversion kit to prep them first.

In most municipalities, you will need a permit to install a permanent home generator, including emergency backup, partial-home, and whole-home generators. A permit for a generator usually costs between $50 and $250, depending on where you live. Your electrician or certified generator installer will usually pull the permit for you—and might be required to do so by your building department—but you’ll be on the hook for the cost of the permit. You should ask your installer before agreeing to any work if they will pull the necessary permits for your project.

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. 

Yes. You can connect your home back-up battery to a generator with its designated charger. Be sure that the output of the generator matches the input requirements for the battery for best results.

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 Derwood, MD homeowners’ guide to generator installs

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