Solar & battery sizing for a whole-home backup
Backup for essential circuits during outages — fridge, freezer, lights, internet and a few outlets — sized for one to two days without grid or sun.
Open this whole-home backup setup in the calculator →
Example daily load
| Device | Power | Use | Energy |
|---|---|---|---|
| Fridge | 150 W | 24 h/day | 3600 Wh |
| Chest freezer | 100 W | 24 h/day | 2400 Wh |
| LED lights | 100 W | 5 h/day | 500 Wh |
| Wi-Fi router | 12 W | 24 h/day | 288 Wh |
| TV | 90 W | 3 h/day | 270 Wh |
| Total | 7058 Wh/day |
Sized system (LiFePO4, 48V, 2 days autonomy)
Open this setup in the calculator — then adjust for your own devices →
Notes for a whole-home backup
These figures assume 4.5 peak sun hours and 2 day(s) of autonomy. If your location is cloudier, your usage is higher, or you want more buffer, increase autonomy or array size. The button above opens the full calculator pre-loaded with this whole-home backup setup, so you can change any device, voltage or chemistry and see the system resize instantly — the example is a starting point, not a prescription.
Frequently asked questions
How many batteries does a whole-home backup need?
For the example load of 7058 Wh/day with 2 day(s) of autonomy on LiFePO4 at 48V, you need roughly 19.98 kWh of battery (416 Ah). Your actual needs depend on your devices and how many cloudy days you want to cover.
What size solar array for a whole-home backup?
About 2273 W at 4.5 peak sun hours, to recharge the daily load. Cloudier locations or higher usage need more.
Looking for a definition or a quick answer? See the solar & battery glossary for terms used on this page, or the FAQ for common sizing questions.
Sources & standards
- NFPA 70 — NEC Article 702, Optional Standby Systems — Transfer-equipment and load-calculation rules for optional standby/backup power, relevant to whole-home battery backup.
- UL 1741 — Inverters, Converters, Controllers and Interconnection System Equipment for Use With Distributed Energy Resources — Safety and grid-interconnection standard for solar/battery inverters.
- IEEE 1547-2018 — Interconnection and Interoperability of Distributed Energy Resources — Technical requirements for connecting solar-plus-storage systems to the utility grid.
- NFPA 855 — Standard for the Installation of Stationary Energy Storage Systems — Clearance, ventilation and fire-safety requirements for stationary battery installations.