Solar Panels for 2-Bedroom House

What Solar System Size Does a 2-Bedroom House Need by Region?

Sunshine is the regional variable. The sizing formula is:

System size (kW) = annual kWh ÷ (peak sun hours per day × 365 × 0.80)

The 0.80 factor is a conservative planning allowance for heat, wiring, inverter, soiling, and shading losses. For reference, NREL’s PVWatts calculator uses default system losses of about 14%, which is a derate of roughly 0.86, so your PVWatts result may be slightly higher than this formula suggests.

Peak sun hours are not hours of daylight. They are the equivalent number of full-intensity hours of sunlight your roof receives per day. NREL-based figures commonly range from about 3.5 in western Washington and Oregon to about 6 in Las Vegas, southern inland California, and western Arizona, with most of the continental U.S. between roughly 4.2 and 5.5. Look up your exact location in PVWatts.

System size and panel count by monthly usage and sun hours (400 W panels)

Panel counts are rounded up to the next whole panel. All values are calculated with the formula above.

Chart summary: The same 550 kWh/month home needs 17 panels at 3.5 peak sun hours but only 10 panels at 6.0, so sunshine alone changes the panel count by about 40% across the range shown. At the 4.5-hour planning value used in this guide, the answer is 13 panels.

Four other factors change the final count:

• Roof orientation and tilt. South-facing roofs generally produce the most. East- or west-facing roofs usually produce less, often by 10% to 20% depending on tilt and location, which can mean one or two extra panels. Model your actual roof in PVWatts.
• Shading. Trees and neighboring buildings can cut output more than orientation does.
• Panel wattage. Higher-wattage panels (for example 430 W instead of 400 W) reduce the count if roof space is limited.
• Future loads. If you plan to add an EV charger or heat pump, ask installers to quote a larger system as well. It is usually simpler to size for those loads at installation than to expand later.

For comparison, see our guide to Solar System Size for a 3-Bedroom House and Solar System Size for a 5,000 sq ft House.

How Long Does Solar Take to Pay for Itself on a 2-Bedroom Home?

Simple payback is net system cost divided by annual bill savings. In the worked example, the 5.2 kW system produces about 6,800 kWh in year one, enough to cover the home’s 6,600 kWh of use. At the 2026 national average residential rate of about 18.3 cents per kWh (EIA data), that is roughly $1,208 per year, or about $100 per month. Against an installed cost of $13,000 to $18,200 with no federal credit, simple payback is about 11 to 15 years, or 13 years at the $3.00/W midpoint.

Your electricity rate is the biggest lever. EIA-based figures for July 2026 put residential prices at roughly 12.7 cents in Louisiana, 15.9 in Texas, 30.5 in Massachusetts, 33.6 in California, and 48.0 in Hawaii. Monthly prices move, so check your current bill. In a per-kilowatt model at $3.00 per watt and 4.5 sun hours, simple payback is about 4.8 years at Hawaii’s 48.0¢, 6.8 at California’s 33.6¢, 7.5 at Massachusetts’ 30.5¢, 12.5 at the national average, 14.4 at Texas’ 15.9¢, and 17.9 at Louisiana’s 12.7¢.

Chart summary: With no federal credit, a $15,600 cash purchase reaches break-even in year 13 at flat electricity rates and in year 12 if rates rise 2% per year. By year 25 the cumulative gain is about $13,700 at flat rates and about $21,800 with 2% growth. Lower installed prices or state incentives would move the break-even earlier; below-retail export credits would push it later.

Net metering matters. The savings model assumes every kWh of solar is valued at your retail rate. Where exported power earns less, payback is longer. California moved to its Net Billing Tariff (NEM 3.0) in April 2023, which credits exports at a fraction of the retail rate, and Arizona and Nevada also pay below-retail export credits. Rules vary by utility and change often, so confirm your export rate before signing.

Degradation and upkeep. A common planning assumption is that panels lose about 0.5% of output per year, which adds a small amount to payback. Inverters may need replacement during the system’s life, a cost not included in these figures.

25-year view. Using the example’s numbers, the system avoids about $29,300 of electricity purchases over 25 years if rates stay flat, against a $15,600 cost, for a net of about $13,700. If rates rise 2% per year, the net is about $21,800. These estimates exclude financing costs, inverter replacement, and any state incentives. Use our solar payback calculator to test your own numbers.

Sources and Methodology

This guide’s figures are calculated with the stated assumptions and checked against these sources, accessed in October 2026:

• U.S. Energy Information Administration, Average Monthly Bill, Residential (2024) and How much electricity does an American home use?; residential prices from Electric Power Monthly, Table 5.6.A.
• IRS, Residential Clean Energy Credit and Public Law 119-21 (One Big Beautiful Bill Act).
• NREL, PVWatts Calculator, for location-specific production and peak sun hours.
• Berkeley Lab, Price Premiums for U.S. Solar Home Sales (2015).
• DSIRE and state agency pages for state incentives and net metering rules.
• 2026 installer and marketplace pricing guides for the $2.50–$3.50 per watt range.

Method. Annual kWh ÷ (peak sun hours × 365 × 0.80) gives system size; panel counts use 400 W panels rounded up. Savings assume solar output offsets usage at the retail rate (18.3¢/kWh national average), with 0.5% annual degradation. Payback is cost divided by first-year savings. Loan payments use standard amortization. This is general information, not financial, tax, or legal advice; consult a qualified professional and get written installer quotes.