Battery & Backup Calculators

Outage planning starts with two connected questions: how much battery capacity do you need, and how long will it actually last? These aren't the same calculation. Start with the backup time calculator to estimate runtime — enter your essential loads and see exactly how many hours a given battery size will sustain them. Then use the battery sizer to work backward from your target outage coverage (overnight vs multi-day) to the kWh capacity required. Running both tools together reveals whether the size you can afford actually meets your coverage goal.

The next decision is backup scope: protecting every circuit versus only the ones that matter most. The whole-home vs essential-loads calculator shows that limiting backup to critical circuits — refrigerator, lights, internet, medical devices — typically cuts required capacity by 40-60%, which often means $5,000-$10,000 less upfront. If you're not committed to battery-only backup, the generator vs battery comparison breaks down 15-20 year total ownership cost across both options including fuel, maintenance, and replacement cycles; for infrequent short outages, a generator often has lower lifetime cost, while batteries win on convenience and long-term economics when outages are frequent or solar is in the picture.

Once you have a plan, stress-test it. The blackout readiness tool runs your setup against 1-day, 3-day, and 7-day outage scenarios — the multi-day case often reveals gaps, especially if you're not solar-paired. The degradation modeler projects how usable capacity declines over 10-15 years so you can build that into your sizing decision rather than discovering it mid-outage. The guides below go deeper: preparing your home for extended outages covers load prioritization and solar recharge strategies; battery storage explained covers chemistry tradeoffs, warranty terms, and real-world cost expectations.