What Size Generator Do I Need
for My Home?
Most people guess too small or spend too much on a unit that's way oversized. This guide walks you through how to figure out exactly what your home needs.
Power outages in Clark County aren't constant, but they happen. Ice storms, wind events, the occasional transformer blowout. If you've sat through one with no heat, no fridge, and no way to charge your phone, you've probably thought about getting a generator.
The question everyone asks is the same: what size do I actually need?
Ryan Newman, owner of Newman Electric in Vancouver, WA, says the biggest mistake he sees is homeowners buying a generator based on a rough guess. "You end up with a portable that can barely run the fridge, or a standby unit that's twice the size you need and cost $5,000 more than it should have." The right approach starts with knowing what you want to power and working backward from there.
Common appliance wattage requirements
Every appliance in your home has a running wattage and a startup wattage. The startup draw is usually 2 to 3 times higher than running. Motors are the worst offenders. Your well pump, AC compressor, and sump pump all surge when they kick on.
| Appliance | Running Watts | Startup Watts |
|---|---|---|
| Refrigerator | 150 - 400 | 1,200 |
| Gas furnace (blower) | 500 - 700 | 1,400 |
| Well pump (1/2 HP) | 1,000 | 2,100 |
| Sump pump (1/3 HP) | 800 | 1,300 |
| Central AC (3-ton) | 3,500 | 4,500 |
| Heat pump | 4,000 - 5,000 | 6,000+ |
| Electric water heater | 4,500 | 4,500 |
| Microwave | 1,000 - 1,500 | 1,500 |
| LED lights (10 bulbs) | 100 | 100 |
| Garage door opener | 550 | 1,100 |
Add up the running watts of everything you want to keep on during an outage. Then add the highest single startup wattage on top of that number. That total is the minimum generator size you should be looking at.
Portable vs standby: two different tools
Portable Generator
- $ $500 to $2,000
- W 3,000 to 12,000 watts
- F Gasoline (some dual-fuel)
- S Manual start, manual connection
Best for occasional, short outages. You have to go outside, start it up, run extension cords or flip a manual transfer switch. Good for the fridge, a few lights, and charging devices. Not great if you're gone when the power drops or if someone in the house has medical equipment.
Standby Generator
- $ $4,000 to $15,000+ (before install)
- W 10,000 to 48,000 watts (10 - 48 kW)
- F Natural gas or propane
- S Automatic startup in seconds
Permanently installed on a concrete pad. Kicks on within 10 to 30 seconds of a power failure with no effort from you. Runs on your existing gas line, so no refueling. This is what most homeowners in Vancouver WA end up going with when they want genuine peace of mind.
How to size it right
There are two schools of thought on generator sizing, and both are valid depending on your situation.
Essentials-only approach: You pick the things that absolutely must stay on. Fridge, furnace blower, a few circuits of lights, maybe the well pump. For most homes in Clark County, that lands you in the 10 to 14 kW range for a standby unit. This keeps the cost down and covers the basics.
Whole-home approach: The generator is sized to run everything in the house at once. You don't have to think about which circuits are on the transfer switch and which aren't. For a typical 2,000 square foot home with gas heat and a 200-amp panel, that's usually 16 to 22 kW. If you have a heat pump or electric water heater, you might need 24 kW or higher.
Ryan's recommendation to most homeowners is simple: if you can swing it financially, go whole-home. "You never call me back wishing the generator was smaller. It's always the other direction."
The transfer switch matters as much as the generator
A transfer switch is what disconnects your home from the utility grid when the generator starts. Without it, your generator would backfeed electricity into the power lines, which can kill utility workers trying to restore power. Washington State requires a transfer switch on every generator installation, and it has to be inspected.
- Manual transfer switch: You physically flip a handle to switch from utility power to generator power. Costs less, works with portable generators. You have to be home to do it.
- Automatic transfer switch (ATS): Detects the outage and switches to generator power automatically. Required for standby generators. No human intervention needed.
Newman Electric installs automatic transfer switches with every standby generator. For portable setups, Ryan's crew can install a manual transfer switch with a designated panel so you're not running extension cords through windows.
"We decided to bite the bullet and get a whole-home generator. Ryan came out as scheduled and we went for it. James did the installation, and was terrific: he worked fast, clean, and efficiently."
James Luttenbacher, Google Review
Fuel type: natural gas vs propane vs gasoline
If you have a natural gas line to your house (most homes inside the City of Vancouver do), that's the simplest option for a standby generator. The gas supply doesn't run out, and you never have to think about refueling. The generator taps into your existing gas line with a dedicated connection.
If you're in an area without natural gas, which includes parts of unincorporated Clark County and most of Cowlitz County, propane is the standard alternative. You'll need a propane tank (typically 250 to 500 gallons for a whole-home unit) and a delivery schedule. The upside is that propane stores indefinitely and the generator runs the same as natural gas.
Gasoline is only realistic for portable generators. It goes stale after 3 to 6 months, you need to store it safely, and you have to refill the tank every 8 to 12 hours during an outage. If you're running a portable, keep at least 10 gallons of treated fuel on hand.
Permits and code requirements in Clark County
Any permanently installed generator in Clark County needs an electrical permit. If you're running a new gas line to the unit, you'll also need a gas/mechanical permit. Inside the City of Vancouver, both permits go through the city's Community Development Department (360-487-7890). Outside city limits, the electrical permit goes through Washington State L&I (360-896-2300).
Placement rules also apply. Most jurisdictions require the generator to sit at least 5 feet from any window, door, or soffit to prevent exhaust from entering the home. Your HOA may have additional setback requirements.
Newman Electric handles the entire permit process for every generator installation. Ryan's crew files the applications, schedules the inspections, and meets the inspector on-site.
"James did everything I expected and quickly with a minimum of power interruptions, which is important because my wife is on continuous supplemental oxygen and we had to use a tank for less than an hour while James completed the wiring. He hauled my 7.5K generator down to the garage and fired it up to test that all worked as needed. Thanks Newman"
Central Point, Google Review
Frequently Asked Questions
What size generator do I need for a 2,000 square foot house?
Most 2,000 square foot homes in the Vancouver WA area need a 16 to 22 kW standby generator to run everything during an outage. If you only want essentials covered (fridge, furnace, well pump, and a few lights), a 10 to 14 kW unit will handle it. Newman Electric does a load calculation specific to your home so you get the right size without overspending.
How much does a whole-home generator cost installed?
A whole-home standby generator with installation, automatic transfer switch, and permit runs between $8,000 and $18,000 in the Vancouver WA area. The price depends on the generator size, fuel source, distance from your panel, and whether a concrete pad already exists. Newman Electric provides free on-site estimates with exact pricing before any work starts.
Do I need a permit for a generator in Clark County?
Yes. Any permanently installed generator requires an electrical permit. Inside the City of Vancouver, permits go through the city (360-487-7890). Elsewhere in Clark County, permits go through Washington State L&I (360-896-2300). If a new gas line is involved, you'll need a separate gas permit too. Newman Electric handles all permitting.
Can I install a generator myself?
Washington State requires a licensed electrician for the electrical connection and transfer switch installation. The transfer switch prevents your generator from backfeeding into the utility grid, which is dangerous for line workers. You can pour the concrete pad yourself, but the electrical and gas connections need to be done by a licensed professional and inspected.
What is the difference between a portable and standby generator?
A portable generator runs on gasoline, costs $500 to $2,000, and requires you to manually start it and plug things in during an outage. A standby generator is permanently installed, runs on natural gas or propane, and turns on automatically within seconds of a power failure. Standby generators cost more upfront but require zero intervention during an outage.
Related Services
Generator Installation
Full service page with pricing, sizing, and installation details
Electrical Panel Upgrade
Your panel needs to support the generator's transfer switch
Whole House Surge Protection
Protect electronics when power comes back on after an outage
Dedicated Circuits
Individual circuits for high-draw appliances
Heat Pump Wiring
Heat pumps are the biggest load to plan for in generator sizing
Electrical Safety Inspection
Make sure your electrical system is ready before adding a generator
Want to talk generator sizing with someone who does this every week?
Newman Electric installs standby and portable generator setups across Vancouver WA, Clark County, and Cowlitz County. Ryan will come out, look at your panel, and tell you exactly what size you need. No charge for the estimate.