Solar battery backup in Washington, DC, Maryland, and Northern Virginia
Battery storage adds backup power capability to a solar system, providing electricity during grid outages and potentially improving financial returns. This guide covers when batteries make sense for DMV homeowners.
How solar batteries work
A battery stores excess solar production during the day for use at night or during outages. Without a battery, excess solar production is sent to the grid (net metering), and you draw from the grid when solar is not producing.
During a grid outage:
- Without a battery: Solar systems automatically shut off for safety. You have no power.
- With a battery: The battery powers essential circuits. Solar continues charging the battery during daylight.
Battery capacity and what it powers
Battery capacity is measured in kilowatt-hours (kWh). Typical residential batteries:
- Tesla Powerwall: 13.5 kWh
- Enphase IQ Battery 5P: 5.0 kWh (stackable)
- Generac PWRcell: 8.6 kWh base (expandable)
What 13.5 kWh can power during an outage:
- Refrigerator: 1–2 kWh per day
- Lights (LED): 0.5–1 kWh per day
- WiFi/router: 0.2 kWh per day
- Phone charging: minimal
- Sump pump: 0.5–1 kWh per day (critical in basement homes)
- Microwave or coffee maker: brief usage, ~1 kWh per use
A single Powerwall can typically power essential loads for 1–2 days without solar input, longer with sunny days.
DMV outage considerations
Summer storms: Thunderstorms and derechos (like the 2012 derecho) can cause multi-day outages, especially in Montgomery County, Fairfax County, and Loudoun County.
Winter ice storms: Ice accumulation on power lines causes outages in Northern Virginia and Maryland suburbs.
Hurricane remnants: Tropical systems can bring high winds and flooding, causing extended outages.
Basement sump pumps: Many DMV homes have basements with sump pumps. A battery can keep the pump running during outages, preventing flooding.
Medical equipment: Homes with medical devices that require electricity should consider battery backup or a generator.
Financial considerations
Battery cost: $10,000–$20,000+ installed, depending on capacity and brand.
Federal tax treatment: Do not assume a battery credit in a 2026 plan. The current IRS residential-clean-energy guidance says the credit is not available for qualifying property placed in service after December 31, 2025; confirm the applicable tax year and facts with the IRS or a tax professional.
Time-of-use optimization: If your utility offers time-of-use rates, you can charge the battery during low-rate periods and discharge during peak rates. This is more relevant in some markets than others.
Backup vs. daily cycling: Using the battery daily for time-of-use optimization may reduce its lifespan compared to keeping it charged primarily for backup.
Battery alternatives
Portable power stations: Jackery, EcoFlow, and similar brands offer 1–3 kWh portable units. Good for short outages and essential devices, but not whole-home backup.
Generators: Propane or natural gas generators can power the whole home but require fuel storage, maintenance, and produce noise and emissions.
Whole-home batteries vs. partial backup
Some installations power only "essential loads" (refrigerator, lights, outlets) through a critical load panel. Others can power the entire home if the battery and inverter are sized appropriately. Whole-home backup costs significantly more.
How to decide if a battery is right for you
Consider a battery if:
- You experience frequent or extended outages
- You have medical equipment requiring power
- You have a basement sump pump
- You work from home and cannot afford downtime
- Your utility has time-of-use rates that favor storage
A battery may not be worth it if:
- Your outages are rare and brief
- You have a reliable backup generator
- Your budget is tight (solar alone still provides significant savings)
How Renovessa helps
The Renovessa solar planner includes battery sizing and cost options. We help you understand whether battery backup makes sense for your specific situation and coordinate quotes that include battery options if desired.