Free tool

Generator sizing calculator

The same engine that sizes our battery fleet also tells you when a load is beyond battery — heavy well pumps, electric heat, and central air call for a continuously fueled Kohler LP standby. Add your loads and see where you land.

Outage Survival Challenge

Step 1 of 5

Pick an outage and find out if your home makes it through.

Expert mode: exact sizing

What do you want to keep running?

Check the circuits that matter and set how many hours a day each one really runs. Appliances cycle — a furnace may only run four hours on a cold day, and a fridge cycles seven. These defaults are winter-typical; adjust them to your home.

W ×hrs/day
W ×hrs/day
W ×hrs/day
W ×hrs/day
W ×hrs/day
W ×hrs/day
Add your own load
Days of backup you want without sun1 day
half a day7 days
Free Sparxx solar array

Solar panels are included at no extra cost with your rental term. Each panel is 400W and generally produces about 80% of rated capacity (320W working).

Season
Your numbers
1,395 W
Draw at once (realistic)
3,195 W
Peak surge
7.2 kWh
Daily use

Your circuits add up to 2,140 W on paper, but fridges, furnaces and pumps cycle independently — the inverter only has to carry about 1,395 W at any one moment.

Generator Control Box load
12%1,395 W / 12,000 W continuous rating

The Sparxx GCB installation manual specifies a maximum continuous load of 12,000 W. Your realistic draw is within the GCB's continuous rating.

How long the battery lasts · Sparxx Turbo Booster
1.8 days
Realistic household runtime

How long the house actually stays livable, using the hours per day each appliance really runs. Without any sun at all: 1.8 days.

6.1 hrs
Full load runtime

Worst case only: every selected circuit running at the same time, nothing cycling off, until the battery is empty. Real homes never run this way.

With the 12-panel array recharging each day, backup stretches to about 5.5 days in winter.

Free solar array · 12 panels
Array rated
4.8 kW
Working output
3.8 kW
Winter harvest
4.8 kWh/day
Net daily draw
2.4 kWh/day

The array could make 9.6 kWh, but the Sparxx Turbo Booster accepts 4.8 kWh of solar input per day — the extra capacity covers cloudy days.

Snow cover, shading, and long cloudy stretches change these numbers. Use the Solar Angle tab to set the tilt and aim that get the most out of the array.

Essentials-only Micro option

The Booster Micro still covers the circuits that matter most

Of what you selected, the Micro can carry Refrigerator, Chest freezer, Furnace / blower, Sump pump, Lights & receptacles, Internet / router / Wi-Fi — about 7.2 kWh a day, roughly 1 days of backup. Food stays cold, the heat stays on, the basement stays dry, and the internet stays up — at $200/mo on a 12-month term.

It's the 240V circuits you added — well pump, water heater, range, dryer — that require a larger unit, not the outage itself.

Compare all three units

Every Sparxx Booster measured against your exact selection. Pick the one you want on your application.

Your selection

Sparxx Turbo Booster

Sustained split-phase power — well pump, water heater, range, and daily solar load shedding.

Output
5 kW
Voltage
120/240V split phase
Solar input
4.8 kWh
Battery
16 kWh
Rental estimate
$400/mo
Month to month
$350/mo
12-mo · year 1
$200/mo
Year 2+
  • Your circuits total 2,140 W, but realistically draw about 1,395 W at once — inside the 5 kW output.
  • 16 kWh covers about 1.8 days of realistic household cycling — or 6.1 hours if every circuit ran nonstop.
  • 12 free panels stretch backup to about 5.5 days in winter.
All Sparxx Booster rentals
UnitMonth-to-monthYr 1Yr 2+
Sparxx Booster Micro$250/mo$200/mo$150/mo
Sparxx Turbo Booster$400/mo$350/mo$200/mo
Sparxx Mega Booster$500/mo$450/mo$250/mo
  • $700 install deposit covers the Sparxx Generator Control Box and sub-feed panel — fully refunded after 6 consecutive rental months.
  • No deposit required if a Generator Control Box is already installed.
  • Placeholder rental available at $75 per two weeks.
  • Maintenance, transfer switch, and gas install: $0 — Sparxx owns and services every generator.
  • Estimates only. Your final rate is confirmed on the rental agreement.

Running watts vs. surge watts

Motors — well pumps, sump pumps, fridge compressors, furnace blowers — pull two to four times their running watts for the first second they start. A generator or inverter that fits your running load can still stall on the surge. This calculator applies each appliance's real surge factor and a diversity factor for loads that never peak together, so the recommendation reflects how a house actually behaves.

When battery isn't enough

Electric heat plus central air, or a deep-well pump with other 240V loads, can exceed what any portable battery system delivers. In those cases the calculator recommends a Kohler 12 kW or 24 kW liquid-propane standby — which Sparxx rents with delivery, installation, and all maintenance handled. Start with the Backup Guide if you'd rather answer questions than add up watts.