Abstract: A home battery backup system is sized for critical loads — refrigeration, lighting, internet, and medical equipment. But many homeowners ask whether pool pumps, water heaters, and other luxury appliances deserve backup priority. The short answer is no. A 10 kWh battery cannot run a 2 kW pool pump and a 4 kW water heater for more than an hour, and diverting energy to them means the fridge and router run out before morning. This article ranks common backup loads by priority and explains how to size your battery accordingly.
The backup priority list
When grid goes down, the battery has limited energy. Decide what matters most:
Priority 1: Keep food safe
- Refrigerator and freezer (100–200 W, cycling)
- Time to backup: 24–48 hours on a 5 kWh battery
Priority 2: Keep communication and medical equipment
- Internet router, modem, phone charger (30–50 W)
- Medical devices (oxygen concentrators, CPAP) — these may need 200–500 W
- Time to backup: 24–72 hours
Priority 3: Keep basic comfort
- LED lighting (50–100 W)
- Ceiling fans
- Garage door opener
- Time to backup: 12–24 hours
Priority 4: Convenience appliances
- TV, computer, kitchen small appliances
- Can run for 2–4 hours on a 10 kWh battery
Not recommended for battery backup:
- Electric water heater (3–4 kW)
- Pool pump (0.5–2 kW)
- Electric oven, induction cooktop (2–3 kW)
- Electric heating (2–5 kW)
- EV charger (3.7–11 kW)
These high-wattage appliances drain a 10 kWh battery in 1–2 hours.
Why pool pumps are a bad backup choice
A typical pool pump draws 0.5–1.5 kW running continuously. Even a 0.75 kW pump:
- Drains a 5 kWh battery in about 5 hours
- Leaves no energy for the fridge overnight
- Pumping pool water during an outage is not a health emergency — your pool can sit for a few days without circulation
If you live in a hurricane or wildfire zone where outages last 3–7 days, you need a generator, not just a battery, to run the pool pump.
Why water heaters are a bad backup choice
An electric water heater draws 3–4 kW. A 10 kWh battery:
- Heats 50 liters of water in 1 hour
- Drains the entire battery in 2–3 hours
- Leaves no backup for the fridge or router
If you have a gas water heater, it does not need electricity (except for the igniter, which uses a trickle). An electric water heater should either:
- Stay off during outages (you can heat water on a gas stove)
- Be backed up by a generator, not the battery
What size battery do you actually need?
If you only back up priorities 1–3 (fridge, router, lights, medical):
- A 5 kWh battery covers most homes for 12–24 hours
- A 10 kWh battery covers larger homes for 24–48 hours
If you also want occasional TV or computer use, add 2–3 kWh.
If you want to run the pool pump or water heater, add 5–10 kWh — but be aware that the battery will not last as long as you expect.
What about whole-home backup?
A "whole-home backup" marketing claim usually means the battery can start large motors (like an air conditioner compressor). It does not mean it can run your entire house for hours.
To run a whole house (10 kW average load) for 4 hours, you need 40 kWh of battery plus a generator for longer outages. That is a 3–4 cabinet installation, not a single wall battery.
Design your backup panel correctly
Ask your installer to set up a dedicated critical-loads panel that includes:
- Fridge and freezer circuits
- Bedroom and hallway lighting
- Router and modem
- Medical equipment circuits
- Garage door opener
Do not include:
- Water heater
- Pool pump
- Oven or stove
- EV charger
- Central air conditioning
If you want to run these occasionally, add a transfer switch and a portable generator.
A practical example
A 10 kWh battery backing up:
- Fridge (150 W cycling, ~0.5 kWh/day)
- Router + lights (100 W for 8 hours = 0.8 kWh)
- TV + laptop (100 W for 3 hours = 0.3 kWh)
- Total: ~1.6 kWh/day
That battery lasts 5–6 days before needing a charge. It is comfortable and reliable.
If you add the pool pump (750 W for 6 hours = 4.5 kWh/day), the battery lasts less than 2 days and you risk the fridge warming up.
Bottom line
Size your battery for essentials first. Add luxury backup only if you have extra capacity. Pool pumps and water heaters belong on a generator, not on the battery.
Ruibit recommends the HZEB-LCT-10 as the sweet spot for most European homes — enough for essentials plus occasional convenience, without overpaying for backup you will never use.
FAQs
Q: Can I run my refrigerator on a 5 kWh battery? Yes. A typical fridge uses about 1 kWh per day. A 5 kWh battery covers the fridge for 3–4 days.
Q: Should I back up my garage door opener? If you need to leave during an outage, yes. It draws little power (100–300 W).
Q: How long can a 10 kWh battery run a fridge? About 5–7 days, assuming the fridge cycles and nothing else is drawing from the battery.
Q: What about sump pumps? If you have a basement and live in a flood zone, a sump pump is a priority. It draws 0.5–1 kW for short cycles. A 5 kWh battery can run it for a few hours over several days.
Q: Can I run my air conditioning on the battery? Central AC draws 2–5 kW. It drains a 10 kWh battery in 2–3 hours. For summer outages, a mini-split on a dedicated circuit is more practical than central AC.
