A whole house generator is the ultimate insurance policy against power outages and the cornerstone of any serious winter emergency kit. Unlike portable generators that require manual setup and only power select circuits, a standby generator sits permanently beside your home, monitors the utility feed, and kicks on automatically within seconds of detecting an outage — whether you are home or not.
For homeowners in New Hampshire and across New England, where nor’easters, ice storms, and summer thunderstorms regularly knock out power for hours or days, a standby generator is not just convenient. It protects your home’s heating system from freezing pipes, keeps the sump pump running to prevent flooding, preserves food in the refrigerator and freezer, and maintains security systems and well pumps that stop working the moment the grid goes down.
The market has several strong options across a range of capacities and price points. Here is how they compare and which one makes sense for your situation. You can find more product guides like this in our Tech section.
How Whole House Generators Work
A standby generator is permanently installed on a concrete pad outside your home, typically near the utility meter. It connects to your electrical panel through an automatic transfer switch (ATS), which constantly monitors the incoming utility power.
When the transfer switch detects an outage, it signals the generator to start. Within 10 to 20 seconds, the generator is running and the transfer switch routes your home’s electrical load from the dead utility line to the generator. When utility power returns, the process reverses — the transfer switch reconnects you to the grid and the generator shuts down.
Most residential standby generators run on natural gas or liquid propane (LP). Natural gas units connect to your existing gas line and provide essentially unlimited fuel as long as the gas utility is operating. Propane models draw from a tank on your property, which gives you fuel independence from utilities but requires periodic refilling.
For rural New Hampshire properties that rely on propane already for heating, a propane-fueled generator integrates naturally into the existing setup. If a full standby installation is beyond your budget, a high-capacity portable power station can cover essential circuits during shorter outages at a fraction of the cost.
Best Overall: Generac Guardian 24kW
Generac dominates the home standby generator market for good reason, and the Guardian 24kW is the company’s flagship residential unit. With 24,000 watts of power, it can run an entire mid-sized home including central air conditioning, an electric range, a well pump, and all the lights and devices you would normally use.
The Guardian features Generac’s proprietary G-Force engine, which is purpose-built for generator use rather than adapted from an automotive or industrial engine. That means it is optimized for the kind of load cycling that generators experience — periods of high demand when the heating system or AC kicks on, followed by lighter loads when those systems cycle off.
The 200-amp whole-house automatic transfer switch is included, which simplifies installation and ensures your entire electrical panel is backed up rather than just selected circuits. Smart monitoring through Generac’s Mobile Link app lets you check generator status, run history, and maintenance schedules from your phone.
For the typical four-bedroom New Hampshire home with central heating, a well pump, and a standard electrical load, the 24kW Generac provides comfortable headroom above your actual demand. That headroom matters because generators are less efficient and wear faster when running at full capacity for extended periods.
Best Budget Option: Generac Guardian 14kW
Not every home needs 24 kilowatts of backup power, and the 14kW Guardian delivers reliable standby protection at a significantly lower purchase and installation cost.
At 14,000 watts, this unit manages essential circuits — heating system, refrigerator, well pump, sump pump, lights, and electronics — without difficulty. Where it requires some planning is with large simultaneous loads. You probably cannot run the electric dryer and the central AC at the same time, but with a 16-circuit transfer switch and some prioritization, you can keep your home functional and comfortable through any outage.
The 14kW uses the same G-Force engine platform as its larger siblings, so reliability and longevity are not compromised by the lower price point. It runs on natural gas or LP, includes the Wi-Fi-enabled Mobile Link monitoring, and carries the same 5-year limited warranty.
For smaller homes, condos, or homeowners who are primarily concerned about keeping the heat running and the pipes from freezing during New Hampshire winters, the 14kW is the right-sized and right-priced solution.
Best Premium: Kohler 26RCAL
Kohler generators have long been the choice of homeowners who prioritize build quality and quiet operation, and the 26RCAL embodies that reputation. With 26,000 watts of output, it comfortably powers large homes and handles high-demand scenarios that would push lesser units to their limits.
The Kohler’s most notable advantage over Generac is its corrosion-resistant aluminum enclosure, which holds up better over decades of outdoor exposure — a meaningful consideration in New Hampshire’s climate of salt air near the coast, road salt spray, and freeze-thaw cycles everywhere. The PowerBoost technology delivers extra starting power for high-inrush loads like air conditioners and well pumps without requiring an oversized generator.
Noise levels are notably lower than comparable Generac units, which matters if your generator pad is near a bedroom window or close to a neighbor’s property. Kohler’s OnCue Plus monitoring system provides remote access similar to Generac’s Mobile Link.
The premium comes at a premium price — the Kohler typically costs 15 to 25 percent more than a comparable Generac for the unit alone, and installation costs can also be higher because fewer electricians stock and service Kohler parts. In areas with strong Kohler dealer networks, that gap narrows.
Best for Natural Gas: Briggs & Stratton 20kW
Briggs & Stratton re-entered the standby generator market with a lineup that emphasizes value for homeowners connected to natural gas. The 20kW model hits a capacity sweet spot for most homes while keeping costs below Generac’s comparable units.
The Symphony II power management module is a standout feature. Rather than simply cutting power to a circuit when demand exceeds capacity, Symphony II manages loads in real time — temporarily cycling the AC compressor or water heater off for a few seconds while the well pump starts, then bringing them back online once the startup surge passes. This intelligent load management effectively lets a 20kW generator handle the same household that might otherwise need a 24kW unit.
The unit runs on natural gas or LP and includes a 200-amp automatic transfer switch. The engine is a commercial-grade Vanguard, which Briggs & Stratton also sells to commercial equipment manufacturers — a sign of its durability.
For New Hampshire homes on natural gas — which includes much of the southern tier of the state — the Briggs & Stratton 20kW offers the best power-per-dollar ratio in the market.
Best for Large Homes: Generac Protector 30kW
Properties over 4,000 square feet, homes with multiple heating and cooling zones, or households with workshops, pools, or other high-draw amenities may need more than the residential-grade units can provide. The Generac Protector 30kW bridges the gap between residential and light commercial generators.
With 30,000 watts of continuous output, the Protector can power virtually any residential load without compromise. You will not need to think about which circuits to prioritize or worry about the AC and well pump starting simultaneously — there is enough capacity for everything.
The Protector runs on natural gas or LP and features a liquid-cooled engine, which is quieter and more durable than the air-cooled engines in smaller residential units. Liquid cooling also maintains more consistent performance in extreme temperatures, both the deep cold of New Hampshire winters and the heat of enclosed installation spaces.
The trade-off is size, noise, and cost. The Protector is physically larger than residential units, requires more clearance from structures, and costs significantly more to purchase and install. But for the right property, it provides peace of mind that nothing short of a fuel supply interruption will affect your home’s power.
Installation: What to Expect
Professional installation of a whole house generator typically takes one to two days and involves a licensed electrician and often a plumber for gas line connections. The process includes pouring or placing a concrete pad, setting the generator, running a gas line from your supply, installing the automatic transfer switch at your electrical panel, and connecting everything.
In New Hampshire, you will need an electrical permit from your town, and many municipalities require a gas permit as well. Some towns also have setback requirements that dictate how far the generator must be from property lines and structures. Your installer should be familiar with local requirements, but it is worth checking with your building department before committing to a specific placement.
Total installed cost varies widely based on unit size, fuel type, electrical panel complexity, and local labor rates. For New Hampshire, expect roughly $5,000 to $8,000 installed for a 14kW unit and $10,000 to $18,000 for a 22-26kW unit, including the transfer switch and all necessary work. These prices can run higher for complex installations requiring extensive gas line work or electrical panel upgrades. Generac’s generator sizing calculator can help you estimate your specific needs, and the Electrical Safety Foundation International (ESFI) provides important safety guidance for any generator installation.
Sizing Your Generator
The most common mistake is undersizing. A generator that runs at or near full capacity during heavy loads will be louder, consume more fuel, and wear out faster than one that has comfortable headroom.
To estimate your needs, add up the wattage of the appliances and systems you want to keep running. A central air conditioner draws 3,000 to 5,000 watts, a well pump takes 1,000 to 2,000, a refrigerator needs 100 to 400, a furnace blower uses 500 to 800, and lights and electronics might add another 1,000 to 2,000. The total gives you a baseline, and you should add 20 to 25 percent for headroom.
Most New Hampshire homes with standard heating, a well pump, and a full electrical load land between 16 and 24 kilowatts. Homes with electric heating, multiple AC units, or shops and outbuildings may need 26kW or more. While a generator handles your electricity, keeping your home warm during extended outages is another matter entirely — many New Hampshire homeowners pair their generator with a wood stove or pellet stove as an independent heat source that works regardless of the grid. For reliable connectivity during those same outages, a mesh WiFi system paired with a battery backup ensures you stay online.
How much does a whole house generator cost installed in New Hampshire?
Total installed cost in New Hampshire ranges from roughly $5,000 to $8,000 for a 14kW unit to $10,000 to $18,000 for a 22-26kW system. This includes the generator, automatic transfer switch, concrete pad, gas line connection, electrical work, and permits. Costs vary based on fuel type, installation complexity, and local labor rates.
What size whole house generator do I need?
Most standard homes need between 16 and 24 kilowatts. To determine your size, add the wattage of all systems you want to back up — heating system, well pump, refrigerator, lights, electronics — and add 20-25% headroom. Homes with electric heating, large AC systems, or workshops may need 26kW or more. A qualified installer can perform a detailed load calculation for your specific home.
How long can a whole house generator run continuously?
Natural gas generators can run indefinitely as long as the gas utility supply remains active. Propane generators run until the tank is depleted — a standard 500-gallon tank can fuel a 22kW generator for roughly 5-8 days under moderate load. Most manufacturers recommend servicing after 200-500 hours of continuous operation, which equates to about 8-21 days of nonstop use.
