Published by Portland Maine Generators
The Two Questions That Decide Everything
First: what must stay on? In a Maine winter, the non-negotiables are heat, water (the well pump, if you're not on town water), the sump pump, and refrigeration. Everything past that, from the range to the dryer to every last light, is a comfort decision. Second: what does your heat actually draw? A gas boiler sips electricity to run circulators and controls. Heat pumps ARE electricity, and they change the entire calculation.
The Ranges That Fit Real Houses
- 10 to 14kW: the essentials machine. Heat, well pump, sump, fridge and freezer, kitchen circuits, and a comfortable number of lights and outlets. For a modest home with fossil-fuel heat, this class keeps the house safe and livable through a week-long outage.
- 18 to 26kW: the whole-house sweet spot. Every circuit in a typical Greater Portland home, no load-shedding decisions, no "don't run the microwave while the well pump is on." This is the class most whole-house installs land in, and the class the cost guide prices in detail.
- 30kW and up: the big-load tier. Large square footage, multiple heat-pump arrays, pools, workshops, and homes with 400-amp services. Some of this tier moves into liquid-cooled machines, with pricing to match.
Why Startup Loads Are the Whole Game
A motor draws far more starting than running: a well pump that runs at 1,500 watts can demand several times that for the second it spins up. Well pumps, sump pumps, furnace blowers, and compressors all do this, and if two of them start at the same moment on an undersized generator, voltage sags and things shut down or, worse, cook slowly. This is why honest sizing uses locked-rotor amps and load management, and why the guy sizing off square footage alone is guessing. Modern systems can also shed low-priority loads automatically, which sometimes lets a smaller, cheaper unit cover a surprisingly big house. That's exactly the judgment call a licensed installer earns their fee on.
Maine-Specific Sizing Realities
- Well pumps are common and hungry. Rural Cumberland County homes almost all have them, and they're routinely the largest single startup load in the house.
- Heat pumps are taking over Maine heating, and a house that heats entirely with them needs its generator sized around their compressors, or a plan for which zones run during an outage.
- Sump pumps run hardest exactly when outages happen: during the storm. An outage plan that doesn't cover the sump pump is a flooded-basement plan.
- Fuel limits size too. A big generator on a small propane tank is a short story. Fuel planning is part of sizing, and the fuel guide covers that half.
The Honest Bottom Line
Oversizing wastes money twice: thousands more up front, and more fuel every running hour, forever. Undersizing fails on the worst night of the year. The fix for both is boring: an actual load calculation at your actual house, which is precisely what the free estimate visit is. If you're weighing whether you need standby power at all, start with the standby-vs-portable comparison; if you already know, get your house sized properly and let the number be the number.