Cooperative Laundromat Water and Energy Recovery Calculator
Overview
This calculator helps a member-owned (cooperative) laundromat estimate how much fresh water and energy for hot-water heating could be saved by adding (1) a greywater reuse system and (2) a drainwater heat recovery system. It converts those physical savings into annual utility-cost savings, then estimates net annual savings (after maintenance) and basic project economics such as simple payback and a discounted payback-style view.
Important: “Heat recovery” is typically a thermal concept (recovering heat from warm wastewater to preheat incoming water). Many laundromats heat water with gas rather than electric resistance. This calculator uses your Energy per load (kWh) as a proxy for the portion of energy that heat recovery can offset. If your site uses gas, you can still use the calculator by converting your estimated gas energy used for water heating into kWh-equivalent (or interpret the “energy rate” as an equivalent $/kWh for thermal energy).
What you’ll need before you start
- Washer throughput: number of washers, typical loads per washer per day, and operating days per year.
- Water use per load: from equipment specs, submetering, or a reasonable average for your mix of machines.
- Utility prices: combined water + sewer price per 1,000 gallons and an energy price per kWh-equivalent.
- Recovery performance: an expected greywater reuse percentage and heat recovery efficiency.
- Project costs: installed capital cost and annual maintenance/consumables/service costs.
Step 1: Estimate annual laundry volume
The model first estimates how many loads you run each year:
Annual loads = washers × loads per washer per day × operating days per year
Step 2: Baseline (no recovery) water use and cost
Baseline annual water use (fresh water going to washers) is:
Baseline water (gal/yr) = annual loads × fresh water used per load (gal)
Cost is calculated using your combined water + sewer rate per 1,000 gallons:
Where:
C w W = baseline annual water use (gal/yr)r w
Step 3: Baseline energy use and cost
Baseline annual energy is:
Baseline energy (kWh/yr) = annual loads × energy per load (kWh)
Baseline annual energy cost is:
Energy cost ($/yr) = baseline energy (kWh/yr) × energy rate ($/kWh)
Interpretation tip: To align with heat recovery physics, try to make “energy per load” represent the portion of energy associated with heating water (not lights, TVs, or unrelated plug loads). If you only have a total electric bill, this will be a rough approximation.
Step 4: Apply greywater reuse and heat recovery
Greywater reuse
The greywater reuse percentage represents the share of baseline fresh water demand replaced by treated/reused water. The calculator estimates:
- Water savings (gal/yr) = baseline water × (greywater % / 100)
- Water cost savings ($/yr) = (water savings ÷ 1,000) × water+sewer rate
Drainwater heat recovery
The heat recovery efficiency represents the fraction of relevant energy that can be recovered (as useful heat) from warm wastewater and used to preheat incoming water. The simplified estimate here is:
- Energy savings (kWh/yr) = baseline energy × (heat recovery % / 100)
- Energy cost savings ($/yr) = energy savings × energy rate
Note: In reality, heat recovery depends on inlet water temperature, drain temperature, flow rates, and how much washing actually uses hot water. Use a conservative efficiency if you have mixed hot/cold cycles or uncertain temperatures.
Step 5: Net savings and payback
After adding water and energy savings, the calculator subtracts annual maintenance:
- Gross savings ($/yr) = water cost savings + energy cost savings
- Net savings ($/yr) = gross savings − annual maintenance cost
Simple payback (years) is then estimated as:
Simple payback = capital cost ÷ net savings
If net savings is zero or negative, simple payback is not meaningful (the project does not pay back under the provided inputs).
Discount rate (time value of money)
The discount rate is used to express that a dollar saved in the future is worth less than a dollar saved today. A higher discount rate makes long payback projects look less attractive. If the calculator provides a “discounted payback” style output, it is generally based on accumulating discounted net savings over time until the initial capital cost is recovered.
How to interpret your results
- Annual loads drives everything; small changes to loads/day can materially change savings.
- Water savings scale with (a) gallons/load and (b) greywater reuse %. If your local sewer fee is high, water reuse becomes more valuable.
- Energy savings are most sensitive to what you put in “kWh per load” and the “energy rate.” If you’re approximating thermal energy with an electric proxy, be explicit when presenting results to a board or lender.
- Net savings is the more decision-relevant number than gross savings for co-ops, because maintenance/filters/service contracts can be non-trivial.
- Payback is a screening metric. For co-ops pursuing resilience and environmental goals, you may also weigh non-financial benefits (water security, marketing, mission alignment) alongside payback.
Worked example (using the default inputs)
Inputs: 28 washers, 5.5 loads/washer/day, 355 operating days/year, 18 gal/load, $13.50 per 1,000 gal, 1.7 kWh/load, $0.18/kWh, 60% greywater reuse, 45% heat recovery, $48,000 capex, $3,200/yr maintenance, 6% discount rate.
- Annual loads = 28 × 5.5 × 355 = 54,670 loads/yr
- Baseline water = 54,670 × 18 = 984,060 gal/yr
- Water savings = 984,060 × 0.60 = 590,436 gal/yr
- Water cost savings = (590,436 ÷ 1,000) × 13.5 ≈ $7,970.89/yr
- Baseline energy = 54,670 × 1.7 = 92,939 kWh/yr
- Energy savings = 92,939 × 0.45 ≈ 41,822.55 kWh/yr
- Energy cost savings = 41,822.55 × 0.18 ≈ $7,528.06/yr
- Gross savings ≈ 7,970.89 + 7,528.06 = $15,498.95/yr
- Net savings ≈ 15,498.95 − 3,200 = $12,298.95/yr
- Simple payback ≈ 48,000 ÷ 12,298.95 = 3.90 years
This example is illustrative: your actual heat recovery savings will depend on how much hot water is used, incoming water temperature, and whether your heating energy is electric or gas.
Scenario comparison table (example)
Use this kind of comparison when discussing options with a cooperative board or sustainability committee.
| Scenario | Greywater reuse | Heat recovery | Typical effect on savings | Common reasons to choose |
|---|---|---|---|---|
| Baseline (no upgrades) | 0% | 0% | No savings | Status quo; defer capex |
| Greywater only | High (e.g., 40–70%) | 0% | Large water/sewer savings; little/no energy effect | High water/sewer prices; water constraints |
| Heat recovery only | 0% | Moderate (e.g., 30–60%) | Energy savings tied to hot-water usage | High energy prices; strong hot-water demand |
| Combined system | Moderate–high | Moderate | Highest gross savings; more maintenance complexity | Mission-driven upgrades; maximize resilience |
Assumptions & limitations
- Energy simplification: Heat recovery is applied as a percent of the provided kWh per load. If that input includes non-heating electricity (lighting, controls, unrelated plug loads), energy savings will be overstated.
- Fuel type not modeled explicitly: The calculator does not separately model gas vs electric water heating. For gas-heated systems, convert to kWh-equivalent or treat the “energy rate” as an equivalent $/kWh of thermal energy.
- No demand charges: Electric demand charges, time-of-use rates, and seasonal price variation are not modeled.
- Greywater constraints: Local codes, permitting, treatment performance, storage needs, and downtime can reduce achievable reuse %. This tool assumes the reuse percentage you enter is achievable and sustained.
- Maintenance uncertainty: Filter replacement, membrane cleaning, disinfection, pumps, and service contracts can vary widely. Use a conservative maintenance estimate for board-level decisions.
- No water heating thermodynamics: The calculator does not compute savings from inlet/outlet temperatures (ΔT), flow profiles, or heat exchanger effectiveness; it uses a simple percent-based approximation.
- Financial scope: Taxes, depreciation, incentives/rebates, financing interest, and grant compliance costs are not included. If incentives cover part of capex, reduce the capital input accordingly.
- Operational changes not included: Behavior changes (more cold-water cycles, different detergents, occupancy shifts) can materially change real savings.
Why Cooperative Laundromats Need a Recovery Calculator
Community-owned laundromats anchor neighborhoods with affordable cleaning services, job creation, and spaces to swap resources. However, they also consume enormous amounts of water and energy. Every load drained into the sewer takes dollars and heat with it. For cooperatives that reinvest profits into members rather than shareholders, trimming utility bills can unlock funds for child care, extended hours, or debt retirement. Yet many operators struggle to translate technical retrofit proposals into real-world savings numbers. Vendors might promise big returns for greywater reuse or heat recovery, but without transparent modeling it is hard to prioritize which upgrade comes first. This calculator helps members weigh options in plain language, centered on cooperative governance rather than corporate spreadsheets.
The inputs reflect questions board members and worker-owners debate at planning meetings: How many washers run daily? What is the utility tariff? How efficient are the machines? What portion of water can we safely recycle after proper filtration? What does the heat recovery loop capture from outgoing wastewater? What does installation cost, and what maintenance budget should we set aside? By plugging these assumptions into the form, cooperatives get an immediate read on annual savings, operating cost reductions per load, greenhouse gas benefits, and payback timelines. The tool also highlights when an upgrade remains financially out of reach without grants or subsidies, empowering members to advocate for public support.
How the Model Works
The calculator estimates baseline water use by multiplying the number of washers by loads per day, operating days per year, and gallons per load. It converts water costs from dollars per thousand gallons into dollars per gallon before multiplying by consumption. The greywater savings represent the portion of fresh water offset by reclaimed water, reducing both purchasing and sewer fees. On the energy side, the tool multiplies loads by electricity per load to get annual kilowatt-hours. Heat recovery efficiency describes the percentage of that energy recaptured to preheat incoming water. By multiplying the captured energy by the electricity rate, the tool calculates avoided costs.
Annual savings combine water and energy reductions, then subtract ongoing maintenance tied to the retrofit. Net savings feed into a discounted payback calculation that considers the time value of money. Rather than quoting a simple payback (capital cost divided by annual savings), the script computes the number of years required for cumulative discounted cash flows to offset the initial investment. If savings never catch up because the discount rate is too high or efficiencies are too low, the tool flags that reality so members are not surprised later.
Key Formula
The discounted payback calculation sums annual savings discounted by the rate entered. In MathML the cumulative value after years is:
where is annual net savings and is the discount rate expressed as a decimal. The calculator increments until meets or exceeds the initial capital cost. If it never does within a 25-year horizon, the result notes that the investment does not pay back under the current assumptions.
Worked Example: Member-Owned Retrofits
Picture a cooperative with 28 washers serving 5.5 loads each per day. Machines draw 18 gallons of fresh water per load and 1.7 kWh of electricity. Water and sewer fees cost $13.50 per thousand gallons, and electricity costs $0.18 per kilowatt-hour. Engineers estimate that a heat recovery loop can capture 45% of waste heat, while a greywater system can safely reuse 60% of water after filtration and disinfection. The upgrades cost $48,000 upfront with $3,200 in annual maintenance. The shop runs 355 days per year, and the co-op uses a 6% discount rate to reflect opportunity costs of capital and inflation.
Baseline water use equals 28 × 5.5 × 355 × 18 = 984,060 gallons annually. At $13.50 per thousand gallons, the co-op spends roughly $13,275 a year on water and sewer. Recovering 60% of that water offsets 590,436 gallons, saving about $7,966 each year. Electricity use totals 28 × 5.5 × 355 × 1.7 = 93,254 kWh. Recapturing 45% of that energy avoids buying 41,964 kWh, which saves $7,553 annually at the given rate. Combined savings reach $15,519. After subtracting the $3,200 maintenance budget, net savings equal $12,319 per year. Discounting those savings at 6% produces a payback just shy of 4.5 years. If members secure rebates, the payback accelerates; if they must finance the capital with loans at a higher rate, the payback lengthens.
Scenario Comparison Table
Use the table to compare retrofit strategies, assuming the same baseline facility described above.
| Scenario | Greywater Reuse | Heat Recovery | Net Savings | Discounted Payback | Notes |
|---|---|---|---|---|---|
| Baseline Retrofit | 60% | 45% | $12,319 | 4.5 years | Matches example |
| Water-Only | 70% | 0% | $6,486 | 7.9 years | Lower capital cost |
| Energy-Only | 0% | 55% | $5,721 | 8.5 years | High energy relief |
| Full Upgrade with Grant | 60% | 45% | $12,319 | 2.2 years | 50% grant support |
The water-only scenario stretches payback because energy waste remains untouched. The energy-only scenario slashes electricity costs but misses water savings, which can be a political goal if the city faces drought. When grants cover half the capital, the cooperative recoups costs in just over two years, strengthening the case for applying to green infrastructure funds.
Resilience and Equity Table
Beyond finances, member-owners care about community outcomes. This table ties technical metrics to resident impact.
| Outcome | Baseline | Retrofit | Change | Community Impact |
|---|---|---|---|---|
| Water Use per Load | 18 gal | 7.2 gal | -60% | Supports drought mandates |
| Energy Use per Load | 1.7 kWh | 0.94 kWh | -45% | Stabilizes rates for members |
| Annual Carbon Emissions* | ~41 metric tons | ~22 metric tons | -19 tons | Improves air quality |
| Emergency Operation Hours (with storage) | 4 | 10 | +6 | Greater disaster resilience |
*Assumes 0.44 kg CO2 per kWh from the grid. Lower emissions reduce strain on frontline neighborhoods already burdened by pollution. Longer emergency operation hours stem from the ability to store reclaimed hot water for hygiene during outages, especially when paired with the resilience hub backup power calculator and the community EV carshare reserve calculator, which together shape a holistic preparedness plan.
Limitations and Assumptions
The model assumes linear savings and uniform loads, yet actual laundromat traffic fluctuates by day of week and season. Some greywater systems may not legally reuse 60% of water depending on local health codes. Heat recovery efficiency can degrade if lint filters are not cleaned or if water temperatures drop. The tool ignores financing costs, taxes, depreciation, and membership dividends. It also does not calculate benefits from bundling upgrades with solar panels modeled in the community solar subscriber balancer. Always consult engineers, accountants, and code officials before making purchases.
Even with those caveats, the calculator arms cooperatives with evidence to negotiate rebates, union-scale labor bids, or community development grants. It reframes efficiency not as austerity but as solidarity—redirecting savings into member needs. Share the narrative in the explanation with lenders, municipal partners, or mutual aid allies to show the breadth of benefits beyond profit.