A three-bedroom house can use very different amounts of electricity depending on the appliances installed, the number of people living in the property, cooking methods, water heating, air conditioning, water pumping and how long electrical equipment operates each day.

There is therefore no single solar-system size that is correct for every three-bedroom house.

One three-bedroom home may operate comfortably with a relatively modest solar system because it uses gas cooking, efficient lighting and limited electrical appliances. Another may require a much larger system because it has electric cooking, several refrigerators, water heating, air conditioning, pumps and extensive electronics.

For solar installation, system sizing, battery backup and electrical services in Kenya, contact 0723763173.

The correct approach is to calculate the home's actual electricity consumption and then determine the required solar panels, inverter and battery capacity.

START WITH ELECTRICITY USE

The first question is not:

“How many solar panels do I need?”

The better question is:

“How much electricity does my three-bedroom house consume?”

Electricity consumption is measured in kilowatt-hours, or kWh.

A solar system should be designed around the home's daily energy requirement.

WHAT A THREE-BEDROOM HOME MAY HAVE

A typical three-bedroom home might contain:

• Television
• Refrigerator
• Freezer
• Wi-Fi router
• LED lighting
• Phones
• Laptops
• Washing machine
• Microwave
• Blender
• Electric kettle
• Iron
• Water pump
• Security system
• CCTV
• Electric cooker
• Water heater
• Air conditioner

Not every home has all these appliances.

The actual combination makes a major difference to solar requirements.

SMALL ELECTRICITY USER

A three-bedroom house with relatively low consumption may use electricity mainly for:

• Lighting
• Television
• Refrigerator
• Internet
• Phones
• Computers
• Security

Such a house may have a daily consumption significantly lower than a property using electric heating and cooking.

The solar system can therefore be smaller.

MEDIUM ELECTRICITY USER

A medium-use home may add:

• Washing machine
• Microwave
• Water pump
• Freezer
• Electric kettle
• Iron
• Additional electronics

The daily energy requirement increases.

The inverter must also handle several appliances operating at the same time.

HIGH ELECTRICITY USER

A high-consumption three-bedroom house may use:

• Electric cooker
• Electric oven
• Water heater
• Air conditioner
• Multiple refrigerators
• Freezer
• Pumps
• Washing machine
• Entertainment systems

This type of home may require a substantially larger solar system.

DAILY ENERGY

The most useful starting point is daily energy consumption.

For example, suppose a household consumes approximately:

8 kWh per day.

The solar array must generate enough energy to supply approximately 8 kWh of useful daily consumption while accounting for system losses.

If the house consumes:

15 kWh per day,

the solar system must be considerably larger.

LOAD CALCULATION

The basic formula is:

ENERGY = POWER × OPERATING TIME

Suppose a television consumes 100 W and operates for five hours.

100 W × 5 hours = 500 Wh

Therefore:

500 Wh = 0.5 kWh.

Repeat this calculation for the major appliances.

SAMPLE LOAD TABLE

A three-bedroom house might have an estimated load profile such as:

Appliance	Power	Daily Use	Approx. Energy
Lighting	150 W	6 hours	0.9 kWh
TV	120 W	5 hours	0.6 kWh
Refrigerator	Variable	—	1.5 kWh
Wi-Fi	15 W	12 hours	0.18 kWh
Computers	150 W	5 hours	0.75 kWh
Washing machine	500 W	1 hour	0.5 kWh
Water pump	750 W	1 hour	0.75 kWh
Microwave	1,200 W	0.3 hour	0.36 kWh
Miscellaneous	—	—	1.0 kWh

The total would then be used as a starting point for solar-system design.

Actual consumption should be measured where possible.

ELECTRICITY BILLS

A utility electricity bill can help estimate consumption.

Suppose the house uses:

240 kWh per month.

Using approximately 30 days:

240 ÷ 30 = 8 kWh/day.

This gives the designer a useful starting figure.

However, the bill does not show exactly which appliances consume the energy.

SMART METER DATA

If detailed electricity data is available, it can improve the design.

The installer can determine:

• Daily consumption
• Peak demand
• Daytime consumption
• Nighttime consumption
• Seasonal changes

This is more useful than guessing based solely on the number of bedrooms.

BEDROOM COUNT DOES NOT DETERMINE SOLAR SIZE

A three-bedroom house can have very different electrical requirements from another three-bedroom house.

For example:

HOUSE A

Gas cooker, solar water heater, efficient lights, one TV and one refrigerator.

HOUSE B

Electric cooker, electric water heater, two refrigerators, freezer, three TVs, air conditioning and large water pump.

Both have three bedrooms.

Their solar requirements can be dramatically different.

SOLAR PANEL SIZE

Once daily energy consumption is known, the solar array can be estimated.

A simplified calculation is:

SOLAR ARRAY ≈ DAILY ENERGY ÷ EFFECTIVE SOLAR HOURS

System losses and design margin must then be included.

The actual design should use appropriate local solar-resource assumptions.

EXAMPLE

Suppose the house consumes:

10 kWh/day.

If the design uses an equivalent solar production assumption of five useful peak-sun hours:

10 ÷ 5 = 2 kW

This is only a theoretical starting point.

Losses, weather, temperature, panel orientation and other factors mean the final PV capacity may need to be higher.

500-WATT PANELS

Suppose the final design requires approximately 4 kW of solar panels.

Using 500 W panels:

4,000 ÷ 500 = 8 panels.

Eight 500 W panels provide:

4 kW nominal PV capacity.

The actual final number depends on the inverter's electrical limits and roof layout.

450-WATT PANELS

If 450 W panels are used:

4,000 ÷ 450 ≈ 8.9.

The practical design would therefore use a suitable number of panels that meets the required capacity and string configuration.

PANEL STRING DESIGN

The panel count is only one part of the design.

The installer must also determine:

• Series configuration
• Parallel strings
• MPPT inputs
• Operating voltage
• Open-circuit voltage
• Input current

The panel configuration must remain within the inverter's specifications.

ROOF SPACE

The three-bedroom house must have enough suitable roof area.

The installer should consider:

• Roof size
• Roof orientation
• Roof pitch
• Shading
• Water tanks
• Chimneys
• Satellite dishes
• Roof structure

Theoretical panel requirements must be checked against the physical roof.

SHADING

Trees can cause significant shading.

Other buildings can also block sunlight.

The installer should inspect the roof at different times of day.

A roof that appears sunny at 9 a.m. may be shaded by a neighboring building at 3 p.m.

INVERTER SIZE

The inverter should be sized according to peak electrical demand.

For example, if the house can draw approximately 5 kW simultaneously, the installer needs an inverter capable of handling the expected load and any relevant surge requirements.

3KW INVERTER

A 3 kW inverter may be appropriate for a modest essential-load system.

However, it may not operate all high-power household appliances simultaneously.

It could be suitable for loads such as:

• Lighting
• TV
• Refrigerator
• Wi-Fi
• Computers
• Small appliances

while excluding heavy electric cooking and water heating.

5KW INVERTER

A 5 kW inverter provides more capacity.

It may be appropriate for a medium household depending on the actual peak load.

However, the installer should still check whether high-power appliances can operate simultaneously.

8KW INVERTER

An 8 kW inverter may be considered for larger residential loads.

It can provide more capacity for:

• Cooking
• Pumps
• Refrigeration
• Washing machines
• Entertainment
• Selected air conditioning

The exact system must still be calculated.

10KW OR LARGER

Large three-bedroom homes with extensive electrical equipment can potentially require 10 kW or more of inverter capacity.

This is particularly possible when the home includes:

• Multiple air conditioners
• Electric cooking
• Water heating
• Large pumps
• Multiple refrigeration systems

BATTERY SIZE

Battery capacity depends on how much electricity the homeowner wants to store.

The main questions are:

• How much energy is used at night?
• How many hours of backup are required?
• Which appliances need to remain operational?
• Is grid electricity available?
• Is the system hybrid or off-grid?

SMALL BATTERY SYSTEM

A smaller battery can support essential loads.

For example:

• Lighting
• Wi-Fi
• TV
• Refrigerator
• CCTV

This can provide backup without attempting to run every appliance.

LARGE BATTERY SYSTEM

A larger battery can support more appliances and longer backup periods.

However, battery capacity increases project cost.

The battery should therefore be selected according to actual requirements.

BATTERY BACKUP EXAMPLE

Suppose the essential household load averages:

1.5 kW.

The homeowner wants:

5 hours of backup.

Energy required:

1.5 × 5 = 7.5 kWh.

The nominal battery capacity must be greater than the theoretical 7.5 kWh requirement because usable capacity and conversion losses must be considered.

WHOLE-HOUSE BACKUP

If the customer wants every appliance to operate during a blackout, the battery requirement can become much larger.

For example, operating:

• Refrigerator
• Lights
• TV
• Washing machine
• Microwave
• Water pump
• Electric cooker
• Water heater

requires significantly more stored energy than operating only essential loads.

DAYTIME SOLAR USE

A three-bedroom home can reduce battery requirements by using solar energy directly during the day.

For example:

• Washing machine during daylight
• Water pumping during daylight
• Charging electronics during daylight
• Running selected appliances during strong solar production

This can reduce the amount of energy that must be stored.

NIGHTTIME LOADS

Nighttime electricity typically comes from:

• Battery
• Grid
• Generator

An off-grid system needs enough battery capacity to supply the nighttime load.

A hybrid system can use the grid when battery energy is insufficient.

ELECTRIC COOKER

Electric cooking is one of the most important factors when sizing a home solar system.

A cooker can have several heating elements.

If multiple elements operate simultaneously, demand can become very high.

A home using an electric cooker may need a significantly larger inverter than a similar house using gas cooking.

ELECTRIC OVEN

Electric ovens also consume significant energy.

If the homeowner wants the oven to run entirely from solar, the solar array, inverter and battery must be designed accordingly.

ELECTRIC KETTLE

An electric kettle can have high instantaneous power but relatively short operating time.

The inverter must handle the power.

The battery does not necessarily need to be extremely large solely because of the kettle's wattage, provided its operating time is short.

MICROWAVE

The same principle applies to microwaves.

A microwave may consume around 1 kW or more while operating but is typically used for short periods.

The inverter must handle the instantaneous demand.

IRON

An electric iron can also have a relatively high wattage.

If several high-power appliances are used simultaneously, the peak load can exceed the inverter's capacity.

WASHING MACHINE

A washing machine can be powered by solar.

However, machines with electric water heating may consume substantially more energy.

The installer should check the actual model specifications.

REFRIGERATOR

Refrigerators are generally suitable for solar systems.

However, compressor startup should be considered when selecting the inverter.

Efficient modern refrigerators can reduce daily energy consumption.

FREEZER

A freezer adds another continuous or cycling load.

If the house has both a refrigerator and freezer, their combined energy consumption should be included.

WATER PUMP

Domestic water pumps can be included in the system.

The pump's motor starting characteristics should be considered.

A system that runs lights and televisions successfully may still struggle to start a large pump if the inverter's surge capability is inadequate.

BOREHOLE PUMP

A borehole pump is a much larger design consideration.

The system must account for:

• Motor size
• Starting characteristics
• Borehole depth
• Head
• Flow
• Daily pumping requirement

Solar water-pumping equipment may be designed separately from the household battery system.

SOLAR WATER HEATING

If the house uses a solar water heater, this can reduce the electrical load that would otherwise be used for water heating.

This can make the photovoltaic solar system smaller.

AIR CONDITIONING

One or more air conditioners can significantly increase solar requirements.

The installer should consider:

• Unit capacity
• Electrical input
• Number of units
• Operating hours
• Compressor behavior

A three-bedroom home with three air conditioners can have a very different energy profile from one without air conditioning.

MULTIPLE TELEVISIONS

Three-bedroom homes may have several TVs.

Although individual TVs generally have modest power consumption, multiple units operating for many hours contribute to total daily energy consumption.

COMPUTERS

If residents work from home, computer usage can become an important load.

The system should include:

• Computers
• Monitors
• Printers
• Routers
• Networking equipment

WORK-FROM-HOME LOADS

Remote work can shift electricity consumption into daytime hours.

This can actually be favorable for solar because the appliances operate while solar generation is available.

HOME SECURITY

Security equipment can include:

• CCTV
• Alarm
• Electric fence
• Gate motor
• Security lights

Some of these operate continuously and therefore contribute to daily energy requirements.

ELECTRIC FENCE

Electric fences normally use relatively modest amounts of energy but operate continuously.

They should still be included in the load calculation.

GATE MOTOR

Gate motors operate intermittently.

Their energy consumption may be small compared with continuous appliances, but their motor-starting current should be considered.

INTERNET AND ROUTERS

Internet equipment is ideal for solar backup because it generally consumes little power and can be important during power outages.

THREE-BEDROOM HOUSE WITH GRID

If grid electricity is available, a hybrid system can be a practical choice.

Solar can supply loads during the day.

The battery can provide backup.

The grid can supplement the system when required.

THREE-BEDROOM HOUSE WITHOUT GRID

If the property has no utility connection, an off-grid system must be designed.

This generally requires:

• Adequate PV capacity
• Sufficient battery storage
• Appropriate inverter
• Proper protection
• Backup planning

HYBRID SYSTEM

A hybrid system can provide:

SOLAR + BATTERY + GRID

This can offer flexibility.

During the day:

Solar can power the house.

Excess energy can charge the battery.

During an outage:

The battery and solar can supply selected loads.

ON-GRID SYSTEM

An on-grid system may be appropriate when the main objective is reducing grid electricity consumption rather than providing backup.

A conventional grid-tied system may not operate during a grid outage unless specifically designed with backup capability.

OFF-GRID SYSTEM

An off-grid system needs to be self-sufficient.

The design must account for periods of lower solar generation.

This can require additional battery capacity and PV generation.

HOW MANY PANELS?

There is no fixed number for every three-bedroom house.

As an illustration:

4 kW PV system

could use approximately:

• 8 × 500 W panels

5 kW PV system

could use approximately:

• 10 × 500 W panels

6 kW PV system

could use approximately:

• 12 × 500 W panels

These are nominal examples.

The actual panel count must be determined by the system design and equipment specifications.

HOW MUCH BATTERY?

Again, there is no single answer.

A three-bedroom home might use:

• Small battery for essential backup
• Medium battery for several hours
• Large battery for whole-house backup
• Multiple batteries for off-grid operation

Battery capacity should be calculated from the actual load.

EXAMPLE SYSTEM

Consider a three-bedroom home with:

Daily consumption: 10 kWh

Peak load: 4.5 kW

Nighttime consumption: 4 kWh

A possible design direction might involve:

• Several kilowatts of PV capacity
• A suitably sized hybrid inverter
• A battery providing several kWh of usable energy

The exact equipment must be selected after detailed calculation.

FUTURE EXPANSION

The homeowner should consider future plans.

Potential additions include:

• Electric vehicle
• Electric cooker
• Water heater
• Air conditioning
• Additional freezer
• Borehole
• Workshop equipment

The system can sometimes be designed with expansion capacity.

ROOF DESIGN

A three-bedroom house may have sufficient roof space, but the available area should be measured.

The installer must account for:

• Panel dimensions
• Walkways
• Roof edges
• Shading
• Structural supports
• Maintenance access

PANEL WEIGHT

The roof structure must be capable of supporting the solar installation.

An assessment should consider:

• Panel weight
• Mounting structure
• Wind forces
• Roof condition
• Structural integrity

MOUNTING

Panels should be mounted using appropriate hardware.

The mounting system must provide:

• Mechanical stability
• Correct panel positioning
• Suitable drainage
• Appropriate weather resistance

CABLE ROUTING

The distance between the roof and inverter affects cable selection.

Longer cable runs can increase voltage drop.

The inverter should therefore be positioned strategically.

INVERTER LOCATION

A suitable location should be:

• Dry
• Accessible
• Well ventilated
• Protected from unnecessary heat
• Safe from physical damage

BATTERY LOCATION

The battery location must follow manufacturer requirements.

Consider:

• Temperature
• Ventilation requirements
• Accessibility
• Physical protection
• Water exposure
• Fire safety

SYSTEM MONITORING

A modern system can allow the homeowner to monitor:

• Solar generation
• Battery state
• Household load
• Grid consumption
• Faults

This helps identify changes in system performance.

SOLAR MAINTENANCE

A three-bedroom home's solar system should be inspected periodically.

Maintenance can include:

• Panel cleaning
• Cable inspection
• Connector inspection
• Inverter inspection
• Battery monitoring
• Mounting inspection
• Earthing checks
• Performance analysis

COMMON SIZING MISTAKES

Avoid choosing the system based only on:

• Number of bedrooms
• Number of panels
• Inverter price
• Battery size

The system should be based on measured electrical requirements.

CHEAPEST IS NOT ALWAYS BEST

A very cheap solar installation may use:

• Undersized cables
• Low-quality batteries
• Inadequate protection
• Poor mounting
• Incorrect inverter sizing

This can result in poor performance and higher long-term costs.

PROFESSIONAL ASSESSMENT

A proper solar assessment should establish:

• Daily kWh
• Peak kW
• Nighttime kWh
• Solar availability
• Roof area
• Shading
• Battery requirement
• Inverter requirement
• Panel requirement
• Future loads

THREE-BEDROOM SOLAR OPTIONS

A practical way to think about three-bedroom homes is through usage levels.

BASIC HOME

Primarily lighting, TV, refrigerator, internet and security.

MEDIUM HOME

Adds washing machine, microwave, pumps, freezer and several electronics.

HIGH-LOAD HOME

Adds electric cooking, water heating, air conditioning and larger pumps.

Each category requires a different system.

CAN SOLAR RUN EVERYTHING?

Yes, if the system is designed accordingly.

However, running every appliance simultaneously may require a large inverter.

The customer may instead choose intelligent load management.

LOAD PRIORITY

A practical household system can prioritize:

ESSENTIAL

• Lights
• Refrigerator
• Internet
• CCTV
• Security

NORMAL

• TV
• Computers
• Washing machine
• Pump

HEAVY

• Oven
• Cooker
• Water heater
• Air conditioning

This approach allows the system to provide reliable backup without requiring the maximum possible system size.

SOLAR DURING POWER OUTAGES

For backup during a blackout, the system must have an inverter architecture capable of supplying the required circuits independently of the grid.

A standard grid-tied system should not be assumed to provide blackout power.

Hybrid systems are commonly used when backup is required.

BATTERY BACKUP PRIORITY

The battery can be reserved for important loads.

This can increase the duration of backup.

For example, if only essential loads average 500 W, a battery will last much longer than if the entire house averages 3 kW.

ENERGY EFFICIENCY

Reducing electricity consumption can reduce solar-system size.

Useful measures include:

• LED lighting
• Efficient refrigerators
• Efficient air conditioners
• Efficient pumps
• Avoiding unnecessary standby loads
• Scheduling heavy appliances during solar production

Energy efficiency is effectively another form of solar capacity.

SOLAR SYSTEM PAYBACK

The financial benefit depends on:

• Electricity consumption
• Solar production
• Equipment cost
• Battery cost
• Grid tariffs
• Maintenance
• System lifespan

A detailed financial analysis should be based on actual consumption.

FINAL SIZING PROCESS

For a three-bedroom house, follow this process:

1. LIST ALL APPLIANCES

Identify the equipment that needs solar power.

2. RECORD POWER RATINGS

Use manufacturer specifications where possible.

3. ESTIMATE OPERATING HOURS

Determine how long each appliance operates.

4. CALCULATE DAILY ENERGY

Convert consumption into kWh/day.

5. DETERMINE PEAK LOAD

Identify which appliances can operate simultaneously.

6. DETERMINE BACKUP REQUIREMENT

Decide which loads must remain operational during outages.

7. SIZE THE SOLAR ARRAY

Calculate the PV capacity required.

8. SIZE THE INVERTER

Match it to peak and surge demand.

9. SIZE THE BATTERY

Match it to nighttime and backup energy requirements.

10. CHECK THE ROOF

Confirm sufficient space and suitable structure.

FINAL ANSWER

There is no universal solar size for a three-bedroom house.

A modest three-bedroom home may require a relatively small solar installation, while a high-consumption home with electric cooking, water heating, air conditioning and pumps may require a much larger system.

The correct system is determined by:

DAILY ENERGY + PEAK LOAD + BACKUP REQUIREMENT + SOLAR RESOURCE + FUTURE LOADS

The number of bedrooms is only a starting point.

For professional solar assessment, panel sizing, inverter sizing, battery sizing, hybrid solar installation, off-grid systems and complete residential solar installation in Kenya, contact 0723763173.

The next topic in the series is how many solar panels are required for a 5 kW inverter, including panel wattage, series connections, MPPT voltage, string sizing and practical installation examples.