Home batteries and portable power stations: size the loads

Portable station or installed system?

A portable power station supplies compatible loads through its outlets. An installed system can support selected household circuits through appropriately designed electrical equipment. The latter adds installation work but may provide automatic operation and better integration. Confirm whether the system delivers the voltage and motor-starting capability your loads require.

A solar generator is usually a battery and inverter paired with solar charging equipment. It does not create energy by itself. Panel output, weather, available daylight and input limits determine recharging. A large battery with a small panel may take much longer to replenish than a promotional image suggests.

Calculate an outage energy budget

For an example 12-hour outage, assume a refrigerator averages 70 W over its cycles, network equipment uses 20 W continuously and three lights use 27 W for five hours. Energy is (70 × 12) + (20 × 12) + (27 × 5) = 1,215 Wh. Adding 100 Wh for phones and other small loads gives 1,315 Wh at the appliances.

At an illustrative 85% delivered-energy fraction, required nominal energy is 1,315 ÷ 0.85 = 1,547 Wh before any extra reserve. Confirm what the manufacturer means by usable capacity to avoid counting losses twice. A 1 kWh unit would not meet this example. Refrigerator starting power also needs checking even though its average consumption is only 70 W.

Power is a separate constraint

A kettle or heater can demand much more instantaneous power than several lights and a router together. Build a simultaneous-load list and check continuous output, surge capability and surge duration. Motor loads such as well pumps require appropriate starting performance and voltage; a generous energy rating alone does not prove compatibility.

Never connect a battery output to household wiring through an improvised backfeed cable. Have a qualified electrician design any connection to building circuits. For medical or other critical loads, agree on an outage plan with the equipment provider and do not rely on a generic consumer runtime estimate.

Estimate bill savings without confusing them with resilience

For an illustrative time-of-use plan, suppose you buy 10 kWh at $0.10/kWh and deliver 9 kWh after losses, avoiding $0.30/kWh peak energy. Gross daily value is (9 × $0.30) − (10 × $0.10) = $1.70. At 200 such days, that is $340 before battery wear, fees and installation cost.

Flat-rate tariffs, limited price spreads or full-value solar export credits can make bill savings much smaller. Compare usable capacity, warranty throughput, remaining capacity guarantees, standby consumption, temperature limits and expansion compatibility. Ask how much energy must remain reserved for outages before estimating the amount available for daily bill management.

Before you request a quote or buy

• Measured or documented watt-hours for priority loads
• Continuous and starting power at the correct voltage
• Usable capacity, conversion losses and reserve policy
• Recharge time with the actual panels or charging source
• Installed electrical scope and warranty throughput limits

Frequently asked questions