Solar and battery backup for Illinois homes on well water

Your well pump runs on electricity, and most are hardwired into the home's electrical panel. When the grid goes down, the pump stops and your pressure tank empties after a few uses: no running water, no flushing, no showers. Michigan's environmental agency also warns that a well that loses pressure can let bacteria into the water system.

Many Chicago-area homes are in this position. The Village of Barrington Hills says most homes there have private wells and septic systems, the Illinois State Water Survey describes Campton Township in Kane County as having one of the highest densities of private wells in Illinois, and McHenry County relies entirely on groundwater for drinking water.

Usually, if it's sized for the pump's starting surge. A well pump can draw up to six times its running power for a moment as it starts, so starting power matters more than storage. Tesla rates Powerwall 3 to start loads drawing up to 185 amps for one second, and FranklinWH rates aPower 2 at 15 kW for 10 seconds and 25 kW for one second.

The range depends on the generator's voltage regulation, and Franklin says two-wire motors need about 50% more. A battery isn't a generator, but the table shows why a 1 HP pump needs a system that can deliver several kilowatts at once.

• A soft starter ramps the pump up gradually. The maker of the SoftStart well pump kit says it cuts starting current by as much as 40%.
• A constant-pressure pump with a variable-speed drive starts gently by design. Grundfos says its SQ pumps have a built-in soft start that brings the motor up to speed within about 2 seconds.
• Load management keeps the pump from starting at the same moment as central air or other big appliances.

Ask installers to check your pump's horsepower and starting current against the battery's specs before you buy.

For essentials plus the well pump, one large battery is often enough, especially with a soft starter. Adding central air, an electric range or a second large pump usually takes two or more. The Illinois rebate of about $300 per kWh covers part of the cost: about $4,050 for one 13.5 kWh battery and $8,100 for two.

Solar recharges the battery on sunny days, which matters most in a multi-day outage. See whole-home vs. essentials backup and Powerwall 3 vs. Enphase vs. FranklinWH.

It depends on the type. A conventional gravity septic system works without electricity. Systems with pumps, such as mound or drip systems and aerobic treatment units, need power, so include the septic pump on your list of backed-up circuits.

1. 1

   Will the battery start my well pump?

   Give them the pump's horsepower and voltage, and ask for the starting current check in writing.

2. 2

   Do I need a soft starter?

   Ask whether one is included and what it costs.

3. 3

   What else is on the backup panel?

   Make sure the well pump, sump pump, septic pump and refrigerator are all covered.

4. 4

   How long will water last in an outage?

   Ask for an estimate with and without solar recharging.

Weighing a generator instead? See standby generator vs. battery.