Electric vs Gas Boiler: The Honest Comparison
The headline arithmetic is blunt: electricity costs several times gas per kWh, and an electric boiler converts it one-to-one — so on running costs, gas wins clearly wherever mains gas exists. Electric boilers earn their place in the gaps: flats without gas or flues, small low-demand properties, and situations where gas infrastructure costs more than the running-cost penalty. And hovering over the whole comparison is the heat pump, which turns the same electricity into 3–4× the heat and rewrites the off-gas answer.
The running cost reality
An electric boiler is ~100% efficient — every kWh becomes heat — but the unit price gap does the damage: with electricity at typically 3.5–4× the gas price, heating a 12,000 kWh-demand home costs correspondingly multiples more than gas, commonly £1,000+ extra per year at standard tariffs. Efficiency percentages in electric-boiler marketing are true and irrelevant; the fuel price ratio is the whole story.
Mitigations exist at the margins — time-of-use tariffs with storage strategies, small well-insulated properties where absolute demand is low — but they narrow the gap rather than close it. Anywhere mains gas is available and usable, the gas boiler wins the running-cost column without suspense.
Where electric boilers genuinely fit
The legitimate niches: flats and apartments without gas supply or viable flue routes (the largest honest market — many blocks simply can't host combustion appliances), small low-occupancy properties where total demand is modest enough that the ratio penalty stays tolerable, annexes and garden buildings, and properties where a gas connection would cost thousands the running penalty won't repay for years.
Within the niche, electric boilers offer real virtues: compact, silent, no flue, no annual combustion servicing, simple installation (£1,200–£2,500 typical), and wet-system compatibility — they drive normal radiators and cylinders, which distinguishes them from panel-heater electrics and preserves the plumbing investment for any future technology change.
The heat pump elephant
For any property weighing electric heating, the heat pump comparison is now mandatory arithmetic: the same electricity delivering 3–4 kWh of heat per kWh (versus the electric boiler's 1) divides the running cost by the SCOP — turning the worst-cost option into a competitive one, with the Boiler Upgrade Scheme supporting the capital side for eligible homes. Off-gas houses choosing between oil, LPG, electric boiler and heat pump increasingly find the pump winning the whole-life sums.
The electric boiler retains the flats-and-constraints territory where outdoor units and cylinders don't fit — but 'no gas here' should trigger the heat pump survey before the electric boiler order, not after. The number of properties where the electric boiler beats both gas and a feasible heat pump is real and small.
Verdicts and edge cases
Decision summary: mains gas available → gas boiler (or heat pump by choice), electric boiler not a contender on cost. Off-gas house with outdoor space → heat pump survey first; oil/LPG comparisons second; electric boiler a distant third. Flat without gas/flue → electric boiler's home ground (with communal/HIU systems and high-heat-retention alternatives considered by building type). Tiny or intermittent-use properties → electric's simplicity can outweigh the ratio.
Edge honesty both ways: don't let an electric boiler's low install quote hide a four-figure annual running penalty in a full-size home — and don't let gas dogma force a £4,000 gas connection into a small flat an electric boiler would serve simply. The comparison is territory-based; knowing which territory you're in is the entire decision.
| Route | Energy used | Cost driver |
|---|---|---|
| Gas boiler @90% | ~13,300 kWh gas | gas unit rate |
| Electric boiler @100% | ~12,000 kWh elec | elec unit rate (3.5–4× gas) |
| Heat pump @SCOP 3.5 | ~3,430 kWh elec | elec rate ÷ 3.5 effectively |
| Install cost context | gas £1,800–£2,800 / elec £1,200–£2,500 / HP £7k–£14k pre-grant |
Making this decision with an engineer
The comparison above gives you the framework; a survey gives you the missing variables — your measured mains flow rate, the room-by-room heat loss, the state of the existing system, and what the pipework and flue routes actually allow. The productive sequence: form a provisional view from this guide, then let a qualified engineer confirm or challenge it with measurements. Quotes sharpen noticeably when the customer clearly understands the options.
Frequently asked questions
Are electric boilers cheaper to run than gas?
No — electricity's unit price at 3.5–4× gas overwhelms the efficiency parity, typically costing £1,000+ more per year in a full-size home. Electric boilers win on fit (no gas, no flue), never on running cost against gas.
Who should actually buy an electric boiler?
Flats without gas or flue routes, small low-demand properties, annexes, and homes where a gas connection costs more than years of the running penalty. Within that territory they're compact, simple and legitimate.
Electric boiler or heat pump for an off-gas house?
Survey the heat pump first: same electricity, 3–4× the heat, grant support available — it usually wins the whole-life sums where it physically fits. The electric boiler is the fallback for constrained properties, not the default.
Do electric boilers need servicing?
No combustion means no flue-gas work — maintenance is minimal (periodic checks of elements, controls and the wet system). It's a genuine ownership simplicity, worth something even where it doesn't decide the comparison.
Where written advice reaches its limit
Guidance like this can tell you what usually causes a symptom, but only an engineer with instruments on your actual appliance can confirm it. If what you're seeing doesn't quite match any pattern described here — or matches several at once — that ambiguity is itself useful information to hand over. Our engineers do this triage daily, and an honest one will tell you on the phone when your problem sounds like a cheap fix, a bigger job, or something that isn't the boiler's fault at all.
Carbon monoxide safety: symptoms, alarms and what to do — essential reading for every home with a fuel-burning appliance.