Commercial Solar vs Alternatives: Honest Comparison

A UK SME with £80,000 of capex available for energy work has five credible paths: on-site solar PV, green tariff procurement, combined heat and power (CHP), heat pump for thermal load, or lighting-only LED retrofit. Each has different costs, different payback profiles, different decarbonisation impacts, and different fits depending on the energy use shape of the business. This page lays out the honest side-by-side comparison — including the cases where solar isn't the right answer. The short version: solar wins for the majority of SMEs because it cuts cost and decarbonises and adds asset value at the same time. But there are specific scenarios where one of the alternatives is a better choice, and we say so.

The five-route side-by-side at £80,000 budget

For a typical UK SME spending £40,000-£60,000 per year on electricity and gas combined, here is what £80,000 of capex delivers under each route. Numbers are for a representative mid-sized business — your specific maths will move depending on operating profile.

1. On-site solar PV — 80 kW system

• Capex: £80,000 turnkey for ~80 kW (£1,000 per kW including all DNO admin, mounting, inverters, commissioning).
• AIA tax relief: 25% × £80,000 = £20,000 year-one. Net effective capex £60,000.
• Annual benefit: 76,000 kWh generated × 70% self-consumption × 24p saving + 30% × 6p SEG = £14,140 per year.
• Simple payback: 4.2 years on net capex, 5.7 years on gross capex.
• 25-year IRR: 17.5% on net capex, 14.0% on gross.
• Carbon impact: Scope 2 reduced by ~35-50% on a typical SME bill (the proportion of imported grid electricity displaced).
• Asset value: EPC uplift one or two bands typically; RICS valuation uplift 1-3%.
• Lifetime: 25-30 years effective, 25-year panel performance warranty.

2. Green tariff (REGO-backed)

• Capex: £0 — operational cost only.
• Premium over standard tariff: typically 5-15% — for a £40k annual bill, £2,000-£6,000 per year additional.
• Annual cost: £2,000-£6,000 every year, indefinitely.
• Carbon impact: debatable. REGO certificates are widely understood as weak — they re-allocate existing renewable generation rather than driving additional renewable build. SBTi and CDP increasingly discount REGO-only claims. Some buyers refuse to accept REGO as evidence of Scope 2 reduction.
• Asset value: none — operational, no EPC change.
• Defensibility: defensible holding position for businesses with no capex headroom or no suitable roof; not a strategic decarbonisation move.

3. Combined Heat & Power (CHP) — 80 kW gas-fired

• Capex: £80,000 covers an 80 kW electrical / 130 kW thermal CHP unit including civils.
• Operating profile required: 5,000+ operating hours per year with continuous thermal demand.
• Annual benefit (best case): 400,000 kWh electrical at marginal grid cost saving plus 650,000 kWh thermal at gas cost saving = £20,000-£35,000 depending on fuel input cost.
• Simple payback: 3-5 years where conditions are met.
• Carbon impact: emits CO2 from gas combustion. As grid intensity falls and gas prices rise, CHP economics degrade and CO2 advantage versus grid disappears. Already in 2026 most modern CHP installations have higher Scope 1+2 footprint than equivalent grid + heat pump.
• Strategic risk: locks in 15-year gas dependency. Net zero policy direction is firmly against new gas combustion in commercial buildings.
• Best fit: hospitals, hotels with leisure, food processing — sites with continuous thermal demand.

4. Heat pump — 80 kW air-source for thermal load

• Capex: £80,000 covers an 80 kW air-source heat pump including buffer tank, controls and integration with existing wet system. Larger commercial heat pumps run £600-£1,000 per kW.
• Annual benefit: replaces gas heating at 80% efficiency with electric heating at 300-400% efficiency (Coefficient of Performance 3-4). For a building with £20,000 per year gas heating bill, replacement saves ~£8,000-£14,000 per year depending on grid electricity price.
• Simple payback: 6-10 years if replacing gas; longer if replacing electric heating already.
• Carbon impact: reduces Scope 1 (gas combustion) at the cost of higher Scope 2 (electricity). Net carbon depends on grid intensity — at 2026 UK grid intensity (~100 gCO2/kWh), heat pump beats gas by 60-75% on lifecycle. Pairing with on-site solar produces near-zero heating emissions.
• Best fit: any site with significant heating demand currently met by gas.

5. LED-only retrofit — comprehensive lighting upgrade

• Capex: typical commercial LED retrofit £15,000-£40,000 — well under £80k budget. Headroom remains.
• Annual saving: 50-70% reduction on lighting load. Lighting is typically 10-25% of total commercial energy. Net bill saving: 5-15%.
• Simple payback: 1-2 years — fastest of any route.
• Carbon impact: material but bounded — caps at lighting share of energy use.
• Best fit: universal — every commercial site benefits from LED retrofit and it should be done before solar to right-size the array.
• Limitation: cannot replace solar or heat pump as a primary decarbonisation strategy — too small in absolute terms.

Why solar wins for most UK SMEs

Solar PV combines four advantages that no other single route delivers together. Cost reduction. 30-60% reduction on electricity bill for the lifetime of the system, with the saving locked in at panels-and-inverter cost (4-8p per kWh effective) versus rising grid retail. Scope 2 carbon reduction that is real, measurable, audit-trail clean — not a REGO claim. EPC uplift that materially improves the building's compliance position with MEES (Minimum Energy Efficiency Standards) — increasingly important as the threshold rises through 2027 and 2030. Asset value uplift recognised by RICS valuers in commercial property valuation. The combination of all four explains why on-site solar has gone from niche specialist purchase to mainstream commercial energy infrastructure across the UK SME base in 2024-2026.

Mathematically: an £80k solar install delivers ~£14k per year of value over 25 years. CHP at the same capex delivers more in years 1-5 if the operating profile fits, but degrades sharply over time. Heat pump delivers comparable value but only addresses heating load. Green tariff delivers no value, just cost. LED-only delivers the fastest payback but caps the prize at 5-15% of total bill. Solar is the broadest and most durable single intervention.

When alternatives win — be honest

CHP wins when: the site runs 5,000+ hours per year with continuous thermal demand alongside power demand. Hospitals, large hotels with leisure facilities and laundries, food processing with steam, breweries, dairies. CHP economics on these sites in 2026 still beat solar in years 1-5 — but the gap is narrowing year by year, and CHP locks in 15 years of gas dependency at a moment when policy direction is firmly the other way. We will quote CHP for genuinely suitable sites but always alongside an alternative solar+heat-pump comparison.

Heat pump wins when: the dominant load is heating rather than power. A medium-sized hotel where gas heating costs £40k per year and electricity is £15k per year — addressing the heating load with a heat pump is the bigger lever. Pairing heat pump with solar produces full decarbonisation across both energy vectors. Choosing heat pump alone (no solar) is a half-measure; we recommend the combination wherever capex headroom allows.

LED-only wins when: total energy bill is under £15,000 per year. Below that level the absolute pounds available for capex don't justify the mobilisation cost of a solar install — LED retrofit captures the meaningful savings without the overhead. Small offices, micro-retail, low-volume hospitality.

Green tariff wins when: there is genuinely no other option. Tenant on a 2-year lease without roof rights, severely structurally compromised building, deeply shaded site. Green tariff is then a defensible holding position while the longer-term decision (relocation, refurbishment, off-site PPA) is worked out.

Stacking strategy: solar + battery + LED + heat pump

For energy-intensive UK businesses with capex headroom, the strongest decarbonisation strategy stacks multiple interventions in sequence. Year 0: LED retrofit (1-2 year payback, 10-25% bill reduction, right-sizes the rest of the plan). Year 1: Solar PV sized to post-LED demand (5-8 year payback, 30-60% bill reduction). Year 2: Battery storage if PV self-consumption sits below 70% — battery captures evening demand offset of summer surplus (8-12 year payback, additional 5-15% reduction). See battery storage for the maths. Year 3-5: Heat pump replacing gas heating, sized to operate primarily on solar+battery output (5-10 year payback, eliminates gas Scope 1 emissions and reduces heating cost long-term). Year 5+: EV charging infrastructure if fleet electrifies, drawing from solar+battery during dwell time.

This stacked approach typically takes a typical mid-market UK SME from baseline £100k+ annual energy spend with significant Scope 1+2 emissions to under £25k annual spend and near-zero direct emissions over 5 years, at a total capex of £200k-£400k spread across the period. Asset finance covers most of this with monthly cost lower than the bill saving from day one. See finance options for full route comparison.

Honest limitations of solar PV

Five scenarios where solar is not the right answer and we say so. Night-shift only operations with near-zero daytime demand. PV generation goes mostly to SEG export at 5-7p versus avoided import at 24p — economics collapse. Very small bills under £15,000 per year where mobilisation costs swamp the prize. Severely shaded sites losing 30%+ of modelled yield to shade. Structurally compromised roofs requiring £30-£60 per square metre reinforcement on top of install cost. Short lease without portability where payback exceeds remaining lease — opt for PPA or skip. We have walked away from quotes in all five categories rather than oversell. See are commercial solar panels worth it for full decision framework.

ESG and procurement context

The procurement and reporting context around UK SME energy decisions is moving fast. Procurement mandates from major buyers (Tesco, Unilever, BMW, IKEA, Microsoft, Google, John Lewis Partnership and an expanding list) are formally requiring suppliers to publish Scope 1 and 2 emissions and demonstrate annual reduction trajectories aligned with Science-Based Targets (SBTi). Suppliers without credible emissions reduction face de-listing or higher cost-of-supply penalties. SECR (Streamlined Energy and Carbon Reporting) applies to large UK companies. Climate-Related Financial Disclosures are mandatory for premium-listed and large unquoted firms, increasingly extending down the supply chain via stakeholder pressure. SDR (Sustainability Disclosure Requirements) phases in through 2026-2027, formalising sustainability claim disclosure standards.

On-site solar PV is the simplest, most defensible Scope 2 reduction available — measurable, locked in for 25+ years, and immune to the REGO weakness that increasingly discounts green-tariff claims. Customers and procurement teams accept it without question. CHP, by contrast, increases Scope 1 emissions and faces growing scrutiny in ESG reporting. Heat pumps are also defensible but require pairing with clean electricity to deliver the full benefit. Solar is the broadest and easiest ESG win available to UK SMEs in 2026.

Decision matrix — which route is right for you

• Office building, 9-5 occupancy, £40k bill: LED first, then solar (high self-consumption, 5-7 yr payback). Skip CHP and heat pump unless gas heating dominates.
• Manufacturing facility, 24/7, £200k bill, gas process heat: LED first, then solar (excellent self-consumption), then heat pump for process heat where COP supports it, IETF grant if eligible. CHP only if process steam at scale.
• Distribution warehouse, 24/7, £150k bill, refrigerated: LED first, then solar (very high self-consumption from chiller load), then battery to capture remaining export.
• Hotel, year-round, £80k bill split power and heating: LED first, then solar, then heat pump replacing gas boilers, possibly CHP if leisure demand is high enough.
• Small retail unit, single-shift, £20k bill: LED retrofit only — solar economics marginal at this scale.
• Tenant on 3-year lease, no roof rights: Green tariff (REGO) until lease decision, then revisit. Possible PPA from off-site solar farm.

Authority resources

Science-Based Targets initiative — emissions reduction methodology: SBTi. UK government net zero strategy: gov.uk Net Zero Strategy. Ofgem on REGO and green tariffs: Ofgem REGO. MCS installer accreditation: MCS. Department for Energy Security and Net Zero — IETF for industrial decarbonisation: IETF.

Related decision pages

For the underlying solar economics: are commercial solar panels worth it. For DNO connection process: G98 application (sub-100 kW) or G99 application (above 100 kW). For sector-specific analysis: industrial solar panels, factories, warehouses, offices, hotels, hospitals, schools. For pricing and finance: cost guide, finance options, grants and funding. For battery integration: battery storage.