The 9-5 Alignment: Why Offices and Solar Are a Perfect Match
Offices and commercial solar PV systems are a near-perfect match. The core working day — 9am to 5pm — aligns almost exactly with peak solar generation. Air conditioning runs hardest on sunny summer days when panels produce the most. And unlike homes that sit empty during daylight hours, offices are full of computers, lighting, and equipment consuming electricity precisely when the sun is shining.
This alignment means offices can achieve 70-90% self-consumption — among the highest of any building type. That translates to substantial savings: a medium-sized office can cut £10,000-£30,000 from annual electricity bills while demonstrating environmental leadership to staff, clients, and stakeholders.
This guide covers everything you need to know — from system sizing and costs to the complexities of multi-tenant buildings, landlord vs tenant decisions, and how solar affects your EPC rating.
Why Offices Are Ideal for Solar
| Factor | Why It Helps |
|---|---|
| 9-5 operation | Core hours match peak solar generation almost exactly |
| High daytime load | IT equipment, lighting, HVAC running throughout working hours |
| Air conditioning demand | Cooling peaks on hot sunny days — exactly when solar output peaks |
| Large flat roofs | Modern office buildings often have extensive flat roof areas |
| High electricity costs | Commercial rates of 25-35p/kWh make savings substantial |
| ESG requirements | Growing pressure for measurable environmental commitments |
| EPC regulations | Solar improves EPC rating, helping meet MEES requirements |
| Staff expectations | Employees increasingly expect sustainable workplaces |
| Client requirements | Many corporate clients assess supplier environmental credentials |
Solar for Offices at a Glance
| Typical system size | 20-200kW (small to large office) |
| Cost range | £15,000-£180,000 |
| Cost per kW | £700-£1,000 installed |
| Annual savings | £4,000-£60,000 |
| Payback period | 4-7 years |
| Self-consumption rate | 70-90% |
| CO₂ savings | 5-100+ tonnes per year |
| Lifespan | 25-30 years |
| EPC improvement | Typically 1-3 bands |
Understanding Office Energy Use
Typical Electricity Consumption
| Office Type | Floor Area | Annual Electricity Use | Annual Bill (at 30p/kWh) |
|---|---|---|---|
| Small office | 200-500m² | 20,000-50,000 kWh | £6,000-£15,000 |
| Medium office | 500-2,000m² | 50,000-150,000 kWh | £15,000-£45,000 |
| Large office | 2,000-5,000m² | 150,000-400,000 kWh | £45,000-£120,000 |
| Corporate HQ/campus | 5,000-20,000m² | 400,000-1,500,000 kWh | £120,000-£450,000 |
Where Office Electricity Goes
| Equipment | % of Office Electricity | When It Runs |
|---|---|---|
| HVAC (heating, cooling, ventilation) | 30-45% | Working hours (cooling peaks with sun) |
| Lighting | 15-25% | Working hours |
| IT equipment (computers, servers) | 20-30% | Working hours + some baseload |
| Small power (desk equipment) | 10-15% | Working hours |
| Lifts and escalators | 3-8% | Working hours |
| Catering/kitchen | 3-8% | Morning and lunchtime |
| Other (security, external) | 5-10% | Various/24/7 |
The Perfect Alignment
Office electricity demand peaks between 10am and 4pm — precisely when solar panels generate most. This creates exceptional self-consumption rates:
| Building Type | Typical Self-Consumption | Why |
|---|---|---|
| Residential home | 30-50% | Occupants often out during peak solar |
| Retail | 50-70% | Good daytime use, but varies by sector |
| School | 60-75% | Good match, but holidays reduce average |
| Office | 70-90% | Near-perfect alignment with 9-5 |
| Industrial (day shift) | 65-85% | Good match if single-shift operation |
Higher self-consumption means more value per kWh generated. Electricity used on-site saves 25-35p/kWh; exported electricity earns only 4-15p/kWh.
System Sizes and Costs by Office Type
Small Office (200-500m²)
| Typical electricity use | 20,000-50,000 kWh/year |
| Recommended system size | 15-35kW |
| Number of panels | 36-84 |
| Roof area needed | 75-180m² |
| Installed cost | £12,000-£32,000 |
| Annual generation | 12,750-29,750 kWh |
| Annual savings (80% self-use) | £3,500-£8,500 |
| Payback period | 4-5 years |
Medium Office (500-2,000m²)
| Typical electricity use | 50,000-150,000 kWh/year |
| Recommended system size | 35-100kW |
| Number of panels | 84-240 |
| Roof area needed | 180-520m² |
| Installed cost | £28,000-£85,000 |
| Annual generation | 29,750-85,000 kWh |
| Annual savings (80% self-use) | £8,000-£24,000 |
| Payback period | 4-5 years |
Large Office (2,000-5,000m²)
| Typical electricity use | 150,000-400,000 kWh/year |
| Recommended system size | 100-250kW |
| Number of panels | 240-600 |
| Roof area needed | 520-1,300m² |
| Installed cost | £75,000-£200,000 |
| Annual generation | 85,000-212,500 kWh |
| Annual savings (80% self-use) | £22,000-£58,000 |
| Payback period | 4-5 years |
Corporate Campus (5,000m²+)
| Typical electricity use | 400,000-1,500,000+ kWh/year |
| Recommended system size | 250kW-1MW+ |
| Number of panels | 600-2,400+ |
| Roof area needed | 1,300-5,200m²+ |
| Installed cost | £180,000-£750,000+ |
| Annual generation | 212,500-850,000+ kWh |
| Annual savings (75% self-use) | £52,000-£210,000+ |
| Payback period | 4-5 years |
Cost Breakdown
Here’s what a typical 75kW office installation includes (for more detailed pricing information, see our commercial solar costs guide):
| Component | Cost |
|---|---|
| Solar panels (180 x 420W) | £18,000-£24,000 |
| Inverter(s) | £5,000-£8,000 |
| Flat roof mounting system | £8,000-£12,000 |
| Cabling, switchgear, metering | £3,000-£5,000 |
| Installation labour | £10,000-£15,000 |
| Scaffolding/access equipment | £1,500-£3,000 |
| DNO application and connection | £500-£2,500 |
| Structural survey | £500-£1,000 |
| Design and project management | £2,000-£4,000 |
| Total | £48,500-£74,500 |
Cost per kW by System Size
| System Size | Cost per kW | Total Cost |
|---|---|---|
| 20kW | £850-£1,000 | £17,000-£20,000 |
| 50kW | £780-£920 | £39,000-£46,000 |
| 75kW | £720-£870 | £54,000-£65,000 |
| 100kW | £700-£850 | £70,000-£85,000 |
| 150kW | £680-£820 | £102,000-£123,000 |
| 250kW | £650-£780 | £162,500-£195,000 |
| 500kW+ | £620-£750 | £310,000+ |
Larger systems benefit significantly from economies of scale — cost per kW drops by 25-35% from small to large installations.
Worked Example: Medium Office Building
Riverside Business Centre is a 1,200m² three-storey office building housing 80 employees across multiple tenants.
Current Situation
| Annual electricity use | 95,000 kWh |
| Current electricity rate | 30p/kWh |
| Annual electricity bill | £28,500 |
| Roof area available | 450m² flat roof |
| Current EPC rating | D |
Proposed System
| System size | 65kW |
| Panels | 156 x 420W |
| Layout | East-west dual tilt on flat roof |
| Annual generation | 55,250 kWh |
| Self-consumption estimate | 85% (46,960 kWh used on-site) |
| Export | 15% (8,290 kWh) |
Financial Analysis
| Installation cost | £52,000 |
| Less: AIA tax relief (25%) | -£13,000 |
| Effective cost after tax | £39,000 |
| Avoided electricity (46,960 kWh × 30p) | £14,088 |
| Export income (8,290 kWh × 8p) | £663 |
| Total annual benefit | £14,751 |
| Simple payback (before tax relief) | 3.5 years |
| Payback after tax relief | 2.6 years |
| Annual bill reduction | 52% |
| New annual bill | £13,750 (vs £28,500 previously) |
25-Year Value
| Total generation (25 years) | 1,330,000 kWh |
| Total savings (with 3% inflation) | £520,000+ |
| Net profit after system cost | £465,000+ |
| EPC improvement | D → B |
Landlord vs Tenant: Who Should Install?
Office buildings are often leased rather than owner-occupied, creating the classic “split incentive” problem: the landlord owns the building but the tenant pays the electricity bill.
Single-Tenant Building (Owner-Occupied)
If you own and occupy the building, the decision is simple:
- You pay for installation
- You receive all savings
- You benefit from improved EPC and asset value
- Payback: 3-5 years after tax relief
Recommendation: Install solar. The business case is compelling.
Landlord-Owned, Single Tenant
| Option | Who Pays | Who Benefits | Considerations |
|---|---|---|---|
| Landlord installs, landlord benefits | Landlord | Landlord (via rent increase or service charge) | Tenant needs to agree; improves EPC and asset value |
| Landlord installs, tenant benefits | Landlord | Tenant (lower bills) | Landlord can justify rent premium; demonstrates green credentials |
| Tenant installs (with permission) | Tenant | Tenant | Need landlord consent; what happens at lease end? |
| Shared investment | Both | Both | Proportional share of savings; works with long leases |
Multi-Tenant Building
Multi-tenant offices add complexity:
- Landlord common areas: Solar can power landlord-controlled areas (reception, lifts, corridors, external lighting) — landlord benefits directly
- Tenant allocation: Solar benefits can be allocated to tenants via service charge reduction
- Sub-metering: Complex arrangements needed if tenants are to benefit directly
Common Approaches
| Approach | How It Works | Best For |
|---|---|---|
| Landlord takes all benefit | Solar offsets common area electricity; tenants unaffected | Buildings with high common area loads |
| Service charge reduction | Solar savings passed to tenants via reduced service charge | Full-service leases |
| Green lease premium | Landlord invests in solar; charges “green premium” on rent | ESG-focused tenants willing to pay more |
| PPA with tenants | Landlord sells solar electricity to tenants at discount to grid | Large buildings with sub-metering |
Tenant Considerations
If you’re a tenant considering funding solar installation yourself:
- Check your lease: Does it permit alterations? Who owns fixtures at lease end?
- Lease length: Is there enough time remaining to recover your investment?
- Landlord consent: Get written permission before proceeding
- End-of-lease terms: Negotiate whether system stays, is removed, or you receive compensation
- Dilapidations: Clarify that solar won’t trigger dilapidations claims
Generally, tenant-funded solar only makes sense with 7+ years remaining on the lease.
EPC Ratings and MEES Compliance
Solar panels significantly improve Energy Performance Certificate (EPC) ratings — increasingly important given tightening regulations.
Current and Future MEES Requirements
| Date | Minimum EPC for Commercial Lettings |
|---|---|
| Current (2024) | E |
| 2027 (proposed) | C |
| 2030 (proposed) | B |
Many office buildings currently rated D or E will need significant improvements to remain lettable. Solar is one of the most cost-effective ways to jump multiple EPC bands.
Typical EPC Improvement from Solar
| System Size (relative to building) | Typical EPC Improvement |
|---|---|
| Small system (10-20% of demand) | 5-15 points (may improve 1 band) |
| Medium system (30-50% of demand) | 15-25 points (typically 1-2 bands) |
| Large system (50%+ of demand) | 25-40+ points (2-3 bands possible) |
A D-rated office with solar can often achieve B or even A, making the building more attractive to tenants and future-proofing against regulations.
Asset Value Impact
Beyond EPC compliance, solar adds tangible asset value:
- Higher rents: Green-certified buildings command 3-10% rental premium
- Lower void periods: ESG-focused tenants prioritise sustainable buildings
- Future-proofing: Avoids costly retrofit before 2027/2030 deadlines
- Exit value: Buyers pay premium for buildings with solar and strong EPC
Air Conditioning: The Perfect Partner
Air-conditioned offices have particularly strong solar economics because cooling demand peaks precisely when solar output peaks:
| Factor | How It Helps |
|---|---|
| Hot sunny days = high cooling demand | AC runs hardest when panels generate most |
| Midday peak cooling | Coincides with midday solar peak |
| Summer intensity | Highest AC use in months with highest solar output |
| Baseload even on mild days | Server rooms, IT areas need cooling year-round |
An air-conditioned office might achieve 85-95% self-consumption on hot summer days — almost perfect alignment.
Example: AC Load vs Solar Generation
A typical air-conditioned office on a hot July day:
| Time | Solar Output (50kW system) | AC + Other Load | Grid Import |
|---|---|---|---|
| 9am | 25kW | 30kW | 5kW |
| 11am | 42kW | 38kW | 0kW (exporting 4kW) |
| 1pm | 48kW | 45kW | 0kW (exporting 3kW) |
| 3pm | 44kW | 42kW | 0kW (exporting 2kW) |
| 5pm | 28kW | 25kW | 0kW (exporting 3kW) |
On this day, the office runs almost entirely on solar — grid import near zero during working hours.
Battery Storage for Offices
Given offices’ high self-consumption, batteries are less critical than for other building types. However, they can still add value:
When Batteries Make Sense
- Evening use: If significant work happens after 6pm
- Demand charge reduction: Some commercial tariffs have expensive peak demand charges that batteries can shave
- Power resilience: Critical operations need backup power
- Grid constraints: If export is limited, batteries store surplus for later use
- Weekend use: Buildings with weekend activity can use stored weekday surplus
When to Skip Batteries
- High daytime self-consumption: If you’re already using 85%+ of generation, batteries add cost with limited benefit
- Standard 9-5 operation: Daytime solar already matches usage well
- Budget constraints: Solar alone delivers better returns than smaller solar + battery
Battery Costs for Offices
| Battery Size | Cost | Best For |
|---|---|---|
| 30kWh | £14,000-£22,000 | Small office, peak shaving |
| 50kWh | £22,000-£35,000 | Medium office, demand management |
| 100kWh | £40,000-£65,000 | Large office, significant evening use |
| 200kWh+ | £75,000-£130,000+ | Campus, resilience requirements |
For most standard offices, we recommend installing solar first without batteries. Monitor actual consumption patterns for 6-12 months, then assess whether batteries would add value.
EV Charging Integration
Office car parks are ideal locations for EV charging, and solar integration makes them even more attractive:
Benefits of Solar + EV Charging
- Staff benefit: Employees arrive with low batteries, leave fully charged — using solar generated during their workday
- Visitor charging: Client and visitor charging as an amenity
- Surplus absorption: EV chargers use any surplus solar that would otherwise export
- Fleet charging: Company vehicles can charge on free solar electricity
- Staff attraction/retention: Free or subsidised workplace charging is increasingly valued
Typical Setup
| Charger type | 7-22kW AC (ideal for all-day parking) |
| Number of chargers | 5-20% of parking spaces initially |
| Cost per charger | £800-£2,500 installed |
| Smart features | Load management, solar integration, payment systems |
| Workplace Charging Scheme grant | Up to £350 per socket (check eligibility) |
Staff parking for 8+ hours means even 7kW chargers deliver meaningful charge — perfect alignment with working day and solar generation.
Car Park Solar Canopies
If roof space is limited but car parking is available, solar canopies offer an alternative:
| What it is | Elevated structure over parking spaces with solar panels as the roof |
| Typical cost | £1,000-£1,500 per kW (including structure) |
| Premium vs roof-mount | 40-70% more expensive |
| Additional benefits | Weather protection for vehicles, natural EV charger location, visible green statement |
| Planning | Usually requires planning permission |
Car park canopies make sense when:
- Roof space is insufficient or unsuitable
- Visible demonstration of sustainability is valued
- EV charging infrastructure is planned anyway
- Premium cost is acceptable for additional benefits
Tax Benefits and Incentives
Capital Allowances
Solar panels qualify for valuable tax relief:
- Annual Investment Allowance (AIA): 100% first-year deduction against taxable profits (up to £1 million)
- Full expensing: For incorporated companies, 100% deduction (through March 2026)
- Effect: A £75,000 solar system reduces taxable profit by £75,000 in year one
Tax Relief Example
| Solar system cost | £75,000 |
| Corporation tax rate | 25% |
| Tax saving (AIA) | £18,750 |
| Effective cost after tax relief | £56,250 |
| Annual savings | £17,500 |
| Payback (after tax relief) | 3.2 years |
VAT
- Installation VAT: 20% standard rate for commercial properties
- VAT recovery: VAT-registered businesses reclaim input VAT
- Net effect: VAT-neutral for most commercial occupiers
Smart Export Guarantee
Exported electricity (the 10-30% not used on-site) earns 4-15p/kWh under SEG. While a small portion of overall savings, it ensures no generated electricity is wasted.
ESG Reporting and Sustainability
Solar delivers measurable ESG metrics that matter to stakeholders:
Scope 2 Emissions Reduction
On-site solar directly reduces Scope 2 (purchased electricity) emissions:
| Grid electricity carbon intensity (2026) | ~180g CO₂/kWh (UK average, declining) |
| Solar electricity carbon intensity | ~20-40g CO₂/kWh (lifecycle) |
| Reduction per kWh | ~140-160g CO₂ |
Example Emissions Savings
| 75kW system annual generation | 63,750 kWh |
| Annual CO₂ saving | 9-10 tonnes |
| 25-year CO₂ saving | 225-250 tonnes |
| Equivalent | ~55 cars off the road for a year |
Reporting Frameworks
Solar supports compliance and reporting under:
- SECR (Streamlined Energy and Carbon Reporting): Reduces reported emissions
- TCFD (Task Force on Climate-related Financial Disclosures): Demonstrates climate action
- CDP (Carbon Disclosure Project): Improves scores for renewable energy use
- Science-Based Targets: Contributes to verified emissions reduction pathways
- Net Zero commitments: Tangible progress towards stated goals
Marketing and Communication
Solar provides compelling content for sustainability communications:
- Real-time generation displays in reception
- Monthly/annual statistics for reports
- Visual imagery of panels for marketing materials
- Staff engagement around sustainability
- Client communications demonstrating environmental leadership
Installation Process
Timeline
| Stage | Duration | Notes |
|---|---|---|
| Initial assessment and quotes | 2-4 weeks | Site visits, usage analysis, proposals |
| Internal approval | Variable | Board approval, landlord consent if applicable |
| Detailed design | 2-3 weeks | Structural survey, electrical design |
| DNO application | 4-10 weeks | Depends on local network and system size |
| Planning (if required) | 8-12 weeks | Usually not required for roof-mount |
| Procurement and scheduling | 2-4 weeks | Equipment ordering, installation booking |
| Installation | 1-3 weeks | Depends on system size |
| Commissioning and handover | 1-2 days | Testing, metering, documentation |
Total timeline: typically 3-6 months from decision to generation.
Minimising Disruption
- Roof work: Almost entirely external — no disruption to office operations
- Electrical connection: May require brief power outage (2-4 hours) — schedule for weekend or evening
- Access: Installer needs roof access route — coordinate to minimise impact
- Noise: Some drilling/construction noise — warn occupants in advance
Procurement Options
Direct Purchase
- Pros: Best long-term returns, own the asset, full control
- Cons: Capital outlay required
- Typical returns: 15-25% IRR
Lease/Hire Purchase
- Pros: Spread payments, preserve capital, still own asset at end
- Cons: Finance costs reduce overall returns
- Typical terms: 5-7 years
Power Purchase Agreement (PPA)
- Pros: Zero upfront cost, immediate savings, no maintenance responsibility
- Cons: Lower savings (10-25% vs 40-60% for owned), long contract (15-25 years)
- Best for: Organisations unable or unwilling to invest capital
Operating Lease
- Pros: Off balance sheet, predictable costs
- Cons: Never own the asset, lower overall benefit
- Best for: Short-term occupancy or balance sheet considerations
Summary
| Aspect | Details |
|---|---|
| Typical system size | 20-200kW (scales with building size) |
| Cost range | £15,000-£180,000 |
| Cost per kW | £650-£1,000 (lower for larger systems) |
| Annual savings | £4,000-£60,000 |
| Payback period | 4-7 years (3-5 years after tax relief) |
| Self-consumption | 70-90% (near-perfect 9-5 alignment) |
| EPC improvement | 1-3 bands (helps meet MEES requirements) |
| CO₂ savings | 5-100+ tonnes per year |
| Tax benefit | 100% AIA reduces effective cost by 19-25% |
| Key advantage | 9-5 operation matches solar generation perfectly |
Office buildings and commercial solar PV systems are an ideal match. The alignment between standard working hours and solar generation creates self-consumption rates of 70-90% — among the highest of any building type. Combined with substantial tax benefits, improving EPC ratings, and growing stakeholder expectations for sustainability, the case for office solar is compelling.
Payback periods of 3-5 years after tax relief, followed by 20+ years of savings, deliver exceptional returns. Whether you’re an owner-occupier, institutional landlord, or commercial tenant, solar makes financial and strategic sense.
For more information on solar PV system types, or to understand typical solar installation costs, see our comprehensive guides. Commercial property owners should also review our detailed commercial solar cost breakdown.
