I manage the purchasing for a mid-sized company. When my VP asked me to "figure out our backup power situation" last year, I wasn't sure where to start. After sorting through specs for a 450 kW Perkins generator in Miami, comparing an 80 kW electric generator for a smaller site, and even looking at a 1000 watt portable solar generator for a remote kiosk, I learned a few things. Here are the 5 steps I now use for any power purchase, whether it's a home natural gas generator or a plan to build a solar generator.
Step 1: Define Your 'Must-Run' Load & Duration
This is where most people mess up. They start looking at generators before knowing what they actually need to power. You don't need to be an electrician for this.
What I do now: I walk through the facility with a clipboard (or a list from the facilities manager) and write down every piece of equipment that absolutely cannot go down. For us, it's the server room, the front-desk phone system, and one fridge with critical samples. We don't need the entire office AC, just the server room cooling.
Check your estimate: Once you have the list, get the running wattage and starting wattage for each item. Your vendor will ask for this. The 80 kW diesel generator we bought for a satellite office is overkill for a small home office, but perfect for our needs. I didn't know that until I did the load calculation.
(Should mention: I once ignored this step and nearly bought a unit that was too small. It would have been a very expensive mistake—ugh.)
Step 2: Decide the Fuel & Form Factor
This is a major cost driver. You have three main choices:
- Diesel: Best for high-power, long-duration use. Think industrial sites. The 450 kW Perkins generator we looked at for our main facility is a beast, but fuel storage and noise are considerations.
- Natural Gas: Great for a home natural gas generator or a building with a gas line. No fuel storage needed. It's what we choose for our new office complex because the city has natural gas infrastructure.
- Solar/Gas Hybrid: If you want to build a solar generator or use a portable one, this is for lower-power needs. A 1000 watt portable solar generator is great for a single workstation but won't power a server room. It's for emergency resilience, not 24/7 backup.
My rule of thumb: If you need more than 10kW for more than 4 hours, diesel or natural gas are the only practical options. If you need less than 1kW, portable solar battery packs are perfect.
Step 3: Get the Specs Dealer-Specific (Don't Just Buy a 'Generator')
This is the step I see people skip the most. They find a 'Perkins generator' online and think all units with that engine are the same. They aren't. The dealer matters.
When I was sourcing that 80 kW electric generator, I called three different Perkins dealers. One offered a standard unit, one offered a sound-attenuated version (good for a quiet neighborhood), and one offered a package with a custom controller. The prices varied by 15%. I only believed this advice after ignoring it and ordering from the cheapest dealer—the unit arrived without the correct circuit breaker panel (ugh).
Always ask for: The specific model number of the generator head, the alternator brand, and the controller type. A 'Perkins' engine is a start, but the complete package (the 'gen-set') is what you're buying.
Step 4: Plan for Installation & Transfer Switch
Don't forget the transfer switch. This is the box that switches your building from grid power to generator power automatically. A generator is useless without it.
Our electrician told me (circa 2024) that installation costs can be 20-30% of the total project for a large unit. For a home natural gas generator, it might be less, but still significant. Get a quote from an electrician before you buy the generator. The quote should include:
- Transfer switch installation
- Concrete pad (if needed)
- Fuel line connection (for gas/natural gas)
- Electrical wiring
For a 1000 watt portable solar generator—well, installation is plugging it in. But for anything over 5kW, get the pro in first.
Step 5: Verify the 'Total Cost of Ownership'
The sticker price isn't the final price. The low price a 450 kW diesel generator in Miami might not include freight, a 5-year warranty, or the first oil change kit.
When I did a vendor consolidation project in 2024, I created a simple spreadsheet. I asked each vendor for their quote, then added:
- Delivery and freight
- Installation (if not included)
- Warranty (3 years vs 5 years)
- Service contract cost per year
- Fuel consumption per hour (e.g., a 450 kW diesel burns about 15-20 gallons/hour under load)
The best price on paper was often not the best price when I added in the 3-year warranty and the higher fuel consumption. The vendor who could provide proper invoicing and a clear service contract saved me time and budget later. It's a small thing, but after 5 years of managing these relationships, dealing with a bad vendor isn't worth a 10% price difference.
Final Thoughts (from a real office manager)
I don't have hard data on industry-wide failure rates for every generator model. But based on managing roughly $50k annually across 8 vendors for different needs, my sense is that 90% of problems come from poor planning (Steps 1 & 4), not from a bad engine. If you're a 20-person company looking at a home natural gas generator, or a facility manager looking at a 450 kW Perkins generator, these steps will work for you. (As of January 2025, pricing on large generators has gone up about 5-10% compared to 2023, so get your quote verified.)
Good luck. And don't forget the transfer switch.
